Thursday, December 31, 2009

What is Embedded System

Embedded system employs a combination of software & hardware to    perform a specific function. It is a part of a larger system which may not be a “computer”Works in a reactive & time constrained environment.
Any electronic system that uses a CPU chip, but that is not a general-purpose workstation, desktop or laptop computer is known as embedded system. Such systems generally use microprocessors; microcontroller or they may use custom-designed chips or both. They are used in automobiles, planes, trains, space vehicles, machine tools, cameras, consumer and office appliances, cell phones, PDAs and other handhelds as well as robots and toys. The uses are endless, and billions of microprocessors are shipper every year for a myriad of applications.
In embedded systems, the software is permanently set into a read-only memory such as a ROM or flash memory chip, in contrast to a general-purpose computer that loads its programs into RAM each time. Sometimes, single board and rack mounted general-purpose computers are called "embedded computers" if used to cont
Embedded System Applications :-
  • Consumer electronics, e.g., cameras, cell phones etc.
  • Consumer products, e.g. washers, microwave ovens etc.
  • Automobiles (anti-lock braking, engine control etc.)
  • Industrial process controller & defense applications.
  • Computer/Communication products, e.g. printers, FAX machines etc.
  • Medical Equipments.
  • ATMs
  • Aircrafts
There are two types of Microcontroller architecture designed for embedded system development. These are:
  1. RISC- Reduced instruction set computer :  RICS stands for Reduced Instruction Set Computer. The philosophy behind it is that almost no one uses complex assembly language instructions as used by CISC, and people mostly use compilers which never use complex instructions. Therefore fewer, simpler and faster instructions would be better, than the large, complex and slower CISC instructions. However, more instructions are needed to accomplish a task. Atmell’s AVR microcontroller based on RISC architecture. 
  2. CISC- Complex instruction set computer : CISC stands for Complex Instruction Set Computer. Most PC's use CPU based on this architecture. For instance Intel and AMD CPU's are based on CISC architectures. Typically CISC chips have a large amount of different and complex instructions. In common CISC chips are relatively slow (compared to RISC chips) per instruction, but use little (less than RISC) instructions. MCS-51 family microcontrollers based on CISC architecture. 
 DIFFERENCE BETWEEN MICROPROCESSORS AND MICROCONTROLLERS:
  • A Microprocessor is a general purpose digital computer central processing unit(C.P.U) popularly known as CPU on the chip. The Microprocessors contain no RAM, no ROM, and no I/P O/P ports on the chip itself. On the other hand a Microcontroller has a C.P.U(microprocessor) in addition to a fixed amount of RAM, ROM, I/O ports and a timer all on a single chip.
  • In order to make a Microprocessor functional we must add RAM, ROM, I/O Ports and timers externally to them,i.e any amount of external memory can be added to it. But in controllers there is a fixed amount of memory which makes them ideal for many applications.
  • The Microprocessors have many operational codes(opcodes) for moving data from external memory to the C.P.U  whereas Microcontrollers may have one or two operational codes.

What is e-commerce

E-commerce (electronic commerce or EC) is the buying and selling of goods and services on the Internet, especially the World Wide Web. In practice, this term and a newer term, e-business, are often used interchangeably. For online retail selling, the term e-tailing is Sometimes used.
E-commerce can be defined from the following perspectives:
  • Communications: From a communication perspective, e-commerce is the delivery of goods, services, information, or payments over computer networks or by any other electronic means. 
  • Commercial (trading): From a commercial perspective, e-commerce provides the capability of buying and selling products, services and information on the Internet and via other online services.
  • Business process:  From a business process perspective, e-commerce is doing business electronically by completing business processes over electronic networks.
  • Service: From a service perspective, e-commerce is a tool that addresses the desire of governments, firms, consumers, and management to cut service costs while improving the quality of customer service and increasing the speed of service delivery.
  • Learning: From a learning perspective, e-commerce is an enabler of online training and education in schools, universities, and other organizations.
  • Collaborative:  From a collaborative perspective, e-commerce is the framework of inter- and intra-organizational collaboration. 
  • Community: From a community perspective, e-commerce provides a gathering place for community members to learn transact and collaborate.
History
The meaning of electronic commerce has changed over the last 30 years. Originally, electronic commerce meant the facilitation of commercial transactions electronically, using technology such as Electronic Data Interchange (EDI) and Electronic Funds Transfer (EFT). These were both introduced in the late 1970s, allowing businesses to send commercial documents like purchase orders or invoices electronically. The growth and acceptance of credit cards, automated teller machines (ATM) and telephone banking in the 1980s were also forms of electronic commerce. Another form of e-commerce was the airline reservation system typified by Sabre in the USA and Travicom in the UK. Online shopping was invented in the UK in 1979 by Michael Aldrich and during the 1980s it was used extensively particularly by auto manufacturers such as Ford,Peugeot-Talbot, General Motors and Nissan. From the 1990s onwards, electronic commerce would additionally include enterprise resource planning systems (ERP), data mining and data warehousing.
Perhaps it is introduced from the Telephone Exchange Office, or maybe not.The earliest example of many-to-many electronic commerce in physical goods was the Boston Computer Exchange, a marketplace for used computers launched in 1982. The first online information marketplace, including online consulting, was likely the American Information Exchange, another pre-Internet online system introduced in 1991.
Although the Internet became popular worldwide in 1994, it took about five years to introduce security protocols and DSL allowing continual connection to the Internet. And by the end of 2000, a lot of European and American business companies offered their services through the World Wide Web. Since then people began to associate a word "ecommerce" with the ability of purchasing various goods through the Internet using secure protocols and electronic payment services.
In the emerging global economy, e-business have increasingly become a necessary component of business strategy and a strong catalyst for economic development. The integration of information and communications technology (ICT) in business has revolutionized relationships within organizations and those between and among organizations and individuals. Specifically, the use of ICT in business has enhanced productivity, encouraged greater customer participation, and enabled mass customization, besides reducing costs.
With developments in the Internet and Web-based technologies, distinctions between traditional markets and the global electronic marketplace such as business capital size, among others-are gradually being narrowed down. The name of the game is strategic positioning, the ability of a company to determine emerging opportunities and utilize the necessary human capital skills (such as intellectual resources) to make the most of these opportunities through an e-business strategy that is simple, workable and practicable within the context of global information and new economic environment. With its effect of leveling the playing field, e-commerce coupled with the appropriate strategy and policy approach enables Small and medium scale enterprises to compete with large and capital-rich businesses.
On another plane, developing countries are given increased access to the global Marketplace, where they compete with and complement the more developed economies. Most, if not all, developing countries are already participating in e-commerce, either as sellers or buyers. However, to facilitate e-commerce growth in these countries, the relatively underdeveloped information infrastructure must be improved.
Current scenario of electronic commerce:
E-commerce is a technology-mediated exchange between parties (individuals or organizations) as well as the electronically based intra-or inter-organizational activities that facilitate such exchanges.
E-commerce consists primarily of the distributing, buying, selling, marketing, and servicing of products or services over electronic systems such as the Internet and other computer networks. The information technology industry might see it as an electronic business application aimed at commercial transactions. It can involve electronic funds transfer, supply chain management, e-marketing, online marketing, online transaction processing, electronic data interchange, automated inventory management systems, and automated data-collection systems. It typically uses electronic communications technology such as the Internet, extranets, e-mail, Ebooks, databases, and mobile phones.
E-commerce brings the universal access of the Internet to the core business processes of buying and selling goods and services. It helps generate demand for products and services and improves order management, payment, and other support functions. The overall goal is to cut expenses by reducing transaction costs and streamlining all kinds of processes.
E-commerce can be divided into:
  • E-tailing or "virtual storefronts" on Web sites with online catalogs, sometimes gathered into a "virtual mall". 
  • The gathering and use of demographic data through Web contacts.
  • Electronic Data Interchange (EDI), the business-to-business exchange of data.
  • E-mail and fax and their use as media for reaching prospects and established customers (for example, with newsletters).
  • Business-to-business buying and selling. 
E-COMMERCE ADVANTAGES 
  • Being able to conduct business 24 x 7 x 365. E-commerce systems can operate all day every day. Your physical storefront does not need to be open in order for customers and suppliers to be doing business with you electronically.
  • Access the global marketplace. The Internet spans the world, and it is possible to do business with any business or person who is connected to the Internet.
  • Speed. Electronic communications allow messages to traverse the world almost instantaneously. There is no need to wait weeks for a catalogue to arrive by post: that communications delay is not a part of the Internet / e-commerce world.
  • Market space. The market in which web-based businesses operate is the global market. It may not be evident to them, but many businesses are already facing international competition from web-enabled businesses.
  • Opportunity to reduce costs. The Internet makes it very easy to 'shop around' for products and services that may be cheaper or more effective than we might otherwise settle for. It is sometimes possible to, through some online research, identify original manufacturers for some goods - thereby bypassing wholesalers and achieving a cheaper price.
  • Computer platform-independent, ‘Many, if not most, computers have the ability to communicate via the Internet independent of operating systems and hardware. Customers are not limited by existing hardware systems' (Gascoyne & Ozcubukcu, 1997:87).
  • Allowing customer self service and 'customer outsourcing'. People can interact with businesses at any hour of the day that it is convenient to them, and because these interactions are initiated by customers, the customers also provide a lot of the data for the transaction that may otherwise need to be entered by business staff. This means that some of the work and costs are effectively shifted to customers; this is referred to as 'customer outsourcing'.
  • Stepping beyond borders to a global view. Using aspects of e-commerce technology can mean your business can source and use products and services provided by other businesses in other countries.
E-COMMERCE DISADVANTAGES AND CONSTRAINTS
  • Time for delivery of physical products. It is possible to visit a local music store and walk out with a compact disc, or a bookstore and leave with a book. E-commerce is often used to buy goods that are not available locally from businesses all over the world, meaning that physical goods need to be delivered, which takes time and costs money. In some cases there are ways around this, for example, with electronic files of the music or books being accessed across the Internet, but then these are not physical goods.
  • Physical product, supplier & delivery uncertainty. When you walk out of a shop with an item, it's yours. You have it; you know what it is, where it is and how it looks. In some respects e-commerce purchases are made on trust. This is because, firstly, not having had physical access to the product, a purchase is made on an expectation of what that product is and its condition. 
  • Perishable goods. Forget about ordering a single gelato ice cream from a shop in Rome! Though specialised or refrigerated transport can be used, goods bought and sold via the Internet tend to be durable and non-perishable: they need to survive the trip from the supplier to the purchasing business or consumer. 
  • Limited and selected sensory information. The Internet is an effective conduit for visual and auditory information: seeing pictures, hearing sounds and reading text. However it does not allow full scope for our senses: we can see pictures of the flowers, but not smell their fragrance; we can see pictures of a hammer, but not feel its weight or balance. If we were looking at buying a car on the Internet, we would see the pictures the seller had chosen for us to see but not the things we might look for if we were able to see it in person.
  • Returning goods. Returning goods online can be an area of difficulty. The uncertainties surrounding the initial payment and delivery of goods can be exacerbated in this process. Will the goods get back to their source? Who pays for the return postage? Will the refund be paid? Will I be left with nothing? How long will it take? Contrast this with the offline experience of returning goods to a shop.
  • Privacy, security, payment, identity, contract. Many issues arise - privacy of information, security of that information and payment details, whether or not payment details (e.g. credit card details) will be misused, identity theft, contract, and, whether we have one or not, what laws and legal jurisdiction apply.
  • Defined services & the unexpected. E-commerce is an effective means for managing the transaction of known and established services, that is, things that are everyday. It is not suitable for dealing with the new or unexpected. For example, a transport company used to dealing with simple packages being asked if it can transport a hippopotamus, or a customer asking for a book order to be wrapped in blue and white polka dot paper with a bow. Such requests need human intervention to investigate and resolve.
  • Personal service. Although some human interaction can be facilitated via the web, e-commerce can not provide the richness of interaction provided by personal service. For most businesses, e-commerce methods provide the equivalent of an information-rich counter attendant rather than a salesperson. 
  • Size and number of transactions. E-commerce is most often conducted using credit card facilities for payments, and as a result very small and very large transactions tend not to be conducted online. The size of transactions is also impacted by the economics of transporting physical goods. 

Wednesday, December 30, 2009

Registers of the 8086 CPU

Four 16-bit registers can be divided into two 8-bit registers
  • AX = AH|AL - Accumulator (Accumulator High|Accumulator Low)  The ax register (Accumulator) is where most arithmetic and logical computations take place. Although you can do most arithmetic and logical operations in other registers, it is often more efficient to use the ax register for such computations.
  • BX = BH|BL - Base (High|Low)- can be used as "pointer"  The bx register (Base) has some special purposes as well. It is commonly used to hold indirect addresses, much like the bx register on the x86 processors.
  • CX = CH|CL - Count (High|Low) - used for counting loops  The cx register (Count), as its name implies, counts things. You often use it to count off the number of iterations in a loop or specify the number of characters in a string.
  • DX = DH|DL - Data (High|Low) - paired with AX for "combined" 16-bit register. DX is high word, AX is low word.  The dx register (Data) has two special purposes: it holds the overflow from certain arithmetic operations, and it holds I/O addresses when accessing data on the 80x86 I/O bus.
4 general purpose registers (AX, BX, CX, DX) are made of two separate  registers, The same is for other 3 registers, "H" is for high and "L" is for low part.


Four 16-bit registers used for Indexing and Stack
  • SI - Source Index - used for indirect addressing 
  • DI - Destination Index - used for indirect addressing.  The si and di registers (Source Index and Destination Index ) have some special purposes as well. You may use these registers as pointers (much like the bx register) to indirectly access memory. You'll also use these registers with the 8086 string instructions when processing character strings. 
  • SP - Stack Pointer - accesses Stack Segment . The sp register (Stack Pointer) has a very special purpose - it maintains the program stack. Normally, you would not use this register for arithmetic computations. The proper operation of most programs depends upon the careful use of this register.  
  • BP - Base Pointer. The bp register (Base Pointer) is similar to the bx register. You'll generally use this register to access parameters and local variables in a procedure. 
Uses of General-Purpose Data Registers
The 16-bit general-purpose data registers AX, BX, CX, DX, SI,  DI, BP, and  SP are provided for holding the following items:
  • Operands for logical and arithmetic operations
  • Operands for address calculations
  • Memory pointers
Although all of these registers are available for general storage of operands, results, and pointers, caution should be used when referencing the ESP register. The ESP register holds the stack pointer and as a general rule should not be used for any other purpose.
General Purpose 16 bit Registers
6 Special Purpose Registers
  • CS (Code); DS (Data); ES (Extra); (SS) Stack segment registers. The 8086 has four special segment registers: cs, ds, es, and ss. These stand for Code Segment, Data Segment, Extra Segment, and Stack Segment, respectively. These registers are all 16 bits wide. They deal with selecting blocks (segments) of main memory. A segment register (e.g., cs) points at the beginning of a segment in memory.  Segments of memory on the 8086 can be no larger than 65,536 bytes long. 
    • CS  The cs register points at the segment containing the currently executing machine instructions. Note that, despite the 64K segment limitation, 8086 programs can be longer than 64K. You simply need multiple code segments in memory. Since you can change the value of the cs register, you can switch to a new code segment when you want to execute the code located there.
    • DS  The data segment register, ds, generally points at global variables for the program. Again, you're limited to 65,536 bytes of data in the data segment; but you can always change the value of the ds register to access additional data in other segments.
    • ES  The extra segment register, es, is exactly that - an extra segment register. 8086 programs often use this segment register to gain access to segments when it is difficult or impossible to modify the other segment registers.  
    • SS  The ss register points at the segment containing the 8086 stack. The stack is where the 8086 stores important machine state information, subroutine return addresses, procedure parameters, and local variables. In general, you do not modify the stack segment register because too many things in the system depend upon it.
General Information about Segment Registers
The segment registers (CS, DS, SS, ES, FS, and GS) hold 16-bit segment selectors. A segment selector is a special pointer that identifies a segment in memory. To access a particular segment in memory, the segment selector for that segment must be present in the appropriate segment register.
When writing application code, programmers generally create segment selectors with assembler directives and symbols. The assembler and other tools then create the actual segment selector values associated with these directives and symbols. If writing system code, programmers may need to create segment selectors directly.
How segment registers are used depends on the type of memory management model that the operating system or executive is using. When using the flat (unsegmented) memory model, the segment registers are loaded with segment selectors that point to overlapping segments, each of which begins at address 0 of the linear address space (as shown in Figure below). These overlapping segments then comprise the linear address space for the program. (Typically, two overlapping segments are defined: one for code and another for data and stacks. The CS segment register points to the code segment and all the other segment registers point to the data and stack segment.)

When using the segmented memory model, each segment register is ordinarily loaded with a different segment selector so that each segment register points to a different segment within the linear address space (as shown in Figure below). At any time, a program can thus access up to six segments in the linear-address space. To access a segment not pointed to by one of the segment registers, a program must first load the segment selector for the segment to be accessed into a segment register.

Each of the segment registers is associated with one of three types of storage: code, data, or stack). For example, the CS register contains the segment selector for the code segment, where the instructions being executed are stored. The processor fetches instructions from the code segment, using a logical address that consists of the segment selector in the CS register and the contents of the IP register. The IP register contains the linear address within the code segment of the next instruction to be executed. The CS register cannot be loaded explicitly by an application program. Instead, it is loaded implicitly by instructions or internal processor operations that change program control (such as, procedure calls, interrupt handling, or task switching).
The SS register contains the segment selector for a stack segment, where the procedure stack is stored for the program, task, or handler currently being executed. All stack operations use the SS register to find the stack segment. Unlike the CS register, the SS register can be loaded explicitly, which permits application programs to set up multiple stacks and switch among them.
  • IP - Instruction Pointer holds address of next instruction   It contains the address of the currently executing instruction. This is a 16 bit register which provides a pointer into the current code segment . The instruction pointer (IP) register contains the offset in the current code segment for the next instruction to be executed. It is advanced from one instruction boundary to the next in straight line code or it is moved ahead or backwards by a number of instructions when executing JMP, Jcc, CALL, RET, and IRET instructions. The IP register cannot be accessed directly by software; it is controlled implicitly by control transfer instructions (such as JMP, Jcc, CALL, and RET), interrupts, and exceptions. The only way to read the IP register is to execute a CALL instruction and then read the value of the return instruction pointer from the procedure stack. The IP register can be loaded indirectly by modifying the value of a return instruction pointer on the procedure stack and executing a return instruction (RET or IRET). 
  • Flag Register  or  FLAGS Register The 16-bit FLAGS register contains a group of status flags, a control flag, and a group of system flags. Figure below  defines the flags within this register.  Some of the flags in the FLAGS register can be modified directly, using special-purpose instructions (described in the following sections). There are no instructions that allow the whole register to be examined or modified directly. However, the following instructions can be used to move groups of flags to and from the procedure stack or the AX register: 
    • LAHF
    • SAHF
    • PUSHF
    • PUSHFD
    • POPF
    • and POPFD.  
After the contents of the FLAGS register have been transferred to the procedure stack or AX register, the flags can be examined and modified using the processor’s bit manipulation instructions (BT, BTS, BTR, and BTC).  When suspending a task (using the processor’s multitasking facilities), the processor automatically saves the state of the FLAGS register in the task state segment (TSS) for the task being suspended. When binding itself to a new task, the processor loads the FLAGS register with data from the new task’s TSS.
When a call is made to an interrupt or exception handler procedure, the processor automatically saves the state of the FLAGS registers on the procedure stack. When an interrupt or exception is handled with a task switch, the state of the FLAGS register is saved in the TSS for the task being suspended.

  • STATUS FLAGS  The status flags (bits 0, 2, 4, 6, 7, and 11) of the FLAGS register indicate the results of arithmetic instructions, such as the ADD, SUB, MUL, and DIV instructions. The functions of the status flags are as follows: 
    • CF (bit 0) Carry flag. Set if an arithmetic operation generates a carry or a borrow out of the most-significant bit of the result; cleared otherwise.This flag indicates an overflow condition for unsigned-integer arithmetic. It is also used in multiple-precision arithmetic.
    • PF (bit 2) Parity flag. Set if the least-significant byte of the result contains an even number of 1 bits; cleared otherwise. 
    • AF (bit 4) Adjust flag. Set if an arithmetic operation generates a carry or a borrow out of bit 3 of the result; cleared otherwise. This flag is used in binary-coded decimal (BCD) arithmetic.
    • ZF (bit 6) Zero flag. Set if the result is zero; cleared otherwise.
    • SF (bit 7) Sign flag. Set equal to the most-significant bit of the result, which is the sign bit of a signed integer. (0 indicates a positive value and 1 indicates a negative value.)
    • OF (bit 11) Overflow flag. Set if the integer result is too large a positive number or too small a negative number (excluding the sign-bit) to fit in the destination operand; cleared otherwise. This flag indicates an overflow condition for signed-integer (two’s complement) arithmetic.
Of these status flags, only the CF flag can be modified directly, using the STC, CLC, and CMC instructions. Also the bit instructions (BT, BTS, BTR, and BTC) copy a specified bit into the CF flag. The status flags allow a single arithmetic operation to produce results for three different data types: unsigned integers, signed integers, and BCD integers. If the result of an arithmetic operation is treated as an unsigned integer, the CF flag indicates an out-of-range condition (carry or a borrow); if treated as a signed integer (two’s complement number), the OF flag indicates a carry or borrow; and if treated as a BCD digit, the AF flag indicates a carry or borrow. The SF flag indicates the sign of a signed integer. The ZF flag indicates either a signed- or an unsigned integer zero.
When performing multiple-precision arithmetic on integers, the CF flag is used in conjunction with the add with carry (ADC) and subtract with borrow (SBB) instructions to propagate a carry or borrow from one computation to the next. The condition instructions Jcc (jump on condition code cc), SETcc (byte set on condition code cc), LOOPcc, and CMOVcc (conditional move) use one or more of the status flags as condition codes and test them for branch, set-byte, or end-loop conditions.
  • DF FLAG The direction flag (DF, located in bit 10 of the FLAGS register) controls the string instructions (MOVS, CMPS, SCAS, LODS, and STOS). Setting the DF flag causes the string instructions to auto-decrement (that is, to process strings from high addresses to low addresses). Clearing the DF flag causes the string instructions to auto-increment (process strings from low addresses to high addresses). The STD and CLD instructions set and clear the DF flag, respectively.
  • System Flags  The system flags register control operating-system or executive operations. They should not be modified by application programs. The functions of the system flags are as follows:
    • IF (bit 9) Interrupt enable flag. Controls the response of the processor to maskable interrupt requests. Set to respond to maskable interrupts; cleared to inhibit maskable interrupts.
    • TF (bit 8) Trap flag. Set to enable single-step mode for debugging; clear to disable single-step mode.
    • IOPL (bits 12, 13) I/O privilege level field. Indicates the I/O privilege level of the currently running program or task. The current privilege level (CPL) of the currently running program or task must be less than or equal to the I/O privilege level to access the I/O address space. This field can only be modified by the POPF and IRET instructions when operating at a CPL of 0.
  • NT (bit 14) Nested task flag. Controls the chaining of interrupted and called tasks. Set when the current task is linked to the previously executed task; cleared when the current task is not linked to another task. 

Negativitis (Negative Thinking)

Does it seem strange that some people COMPLAIN they don’t have enough TIME to be happy, yet they find enough time to be sad? Not really. You see, their deplorable plight has nothing to do with having sufficient or insufficient time. It has everything to do with complaining. After all, complaining is the negation of happiness. It’s impossible to complain and be happy at the same time.
So, beware of that insidious disease known as ‘negativitis’ (negative thinking). It is as pervasive as the common cold, but far more damaging. It mutilates, cripples, and corrodes the human spirit. Those infected by it are broken men and women aimlessly plodding along. The dark clouds brooding over them obscure their vision and cause them to become confrontational, apathetic, and cynical. Their lives are like flat champagne, without any sizzle. So, how do we inoculate ourselves against such a harmful disease? It was only after learning about the horrible effects of smoking that people began to give it up. It may be wise to do the same here. So, let’s review the effects of negativitis.
  1. Complaining is worse than doing nothing, for it is digging the rut one is in deeper and deeper. Each time one complains, it becomes increasingly difficult to climb out of the ditch they’ve created. To loosen the grip of this vicious habit, we need to become aware of our complaining, stop it in its tracks, and immediately look for something positive to say. It’s just a matter of replacing a bad habit with a good one.
  2. A negative attitude is self-defeating. We won’t find solutions to life’s problems by looking for someone or something to blame. Those who say, "Positive thinking doesn't work for me," have got it backwards. It’s not positive thinking that has to work; YOU have to work. For example, you have to work at appreciating what you have instead of moaning about what you lack.
  3. Failure to do what you want to do (be happy) causes physical and mental stress. A rotten attitude, not only delays success, but also shortens life by damaging the immune system (to learn more on how your thoughts affect your immune system, investigate psychoneuroimmunology). So, besides the diseases directly caused by stress, such as heart disease and ulcers, we become susceptible to all manner of other diseases because of a weakened immune system.
  4. Do you know anyone with a negative attitude? How many years have they been that way? Two years? Five years? Ten years? That’s how many years of happiness and success they have robbed themselves of. Blinded by their own negativity, they are prevented from seeing the good around them.
  5. One characteristic of negative thinkers is their need to have the world behave according to their wishes. They have never grown up and still live with childish demands. Whenever people and the world fail to act according to their selfish wishes, they are unhappy. Such a poisonous attitude prevents them from growing and learning how to cope with life's challenges.
  6. Everything negative we say about ourselves to ourselves (self-talk) and to others is a suggestion. We are unwittingly practicing self-hypnosis, programing ourselves for failure, and creating self-fulfilling prophecies.
  7. The negative world of our imagination creates a negative world that is real and one that we are forced to live in. Take Ralph, for example. He’s always complaining about life. “Nowadays people are rude and surly. No matter where you go or what you do, you have to deal with ill-bred people.” As he said this, we made our way to a coffee shop. Once inside, we were greeted by a cheerful chap who asked us what we would like. Sighing (as if it took a great effect to speak), Ralph, almost inaudibly, ordered a medium sized regular coffee. When it arrived, he started complaining. Pointing to the cup, he said, “This is medium?” Without waiting for a response, he added, “You should have told me your cups are so small; I would have ordered a large one if I knew.” Despite the long line that Ralph was holding up, the man behind the counter tried to be patient. Without complaint, he took away the small coffee and replaced it with a large one. As soon as it arrived, Ralph looked at it aghast and bellowed, “You call this regular? There’s not enough cream!” The man behind the counter, who only moments ago was cheerful was now upset and sarcastically replied, “Yes, for MOST people, this is regular, but if you INSIST, I’ll put in more cream. Perhaps next time you may want to ask for DOUBLE cream!” I was next, so I got my coffee and joined Ralph at the table. “See,” he told me, “what did I say to you? People are rude.” Yes, in Ralph’s world, people ARE rude, but what he does not realize is he makes them so.
  8. A particularly pernicious effect of ‘negativitis’ is that it sets one up for the mentality of a victim. Those with a woe-is-me attitude sit around in misery, waiting to be rescued. But they wait in vain because no one can rescue them from their own attitude. They are the only ones who can change it. And until they do so, they are condemned to continue suffering.
  9. Another adverse effect of negativity is that it sets one up for the magic-bullet-syndrome. That is, the victim of ‘negativitis’ spends their time looking for a quick, easy fix, when none exists. By denying a fundamental law of life that states anything worthwhile requires effort to achieve, they achieve nothing. They won’t make progress until they realize that nothing in life is free. They’ve got to be willing to do what it takes to get what they want.
  10. Also, beware of the fact that negative people attract other complainers. Because those who live in a world of doom and gloom alienate others, they have no choice but to look for other negative people to associate with. They then feed off one another and get locked in a clique of losers.
  11. The constant stress that flows from a negative attitude also saps one’s energy, focus, and motivation. It is hardly a formula for success.
  12. Also of great concern is the fact that those who refuse to work on improving their negative attitude may slide into depression, self-pity, and hopelessness.
  13. Additionally, negative people not only harm themselves; they harm the world. They cease to make a contribution to it. Instead of helping, they spread gloom and misery everywhere. If they insist on infecting others, why not infect them with laughter? If they must carry something contagious, why not carry a smile?
Imagine being in a small boat drifting in a river. And imagine being unaware that your boat has a motor. As long as you fail to use that motor you will be a captive of the river. You will be a prisoner without any control over your destination. Yet, the boat that we’re in does have a motor. We can use it to change course. That motor is our power of choice. All we have to do is choose to look for the good, for when we do so, that is all we will find!

Education and the Internet

In the late l9th century, compulsory elementary schooling for all took hold as a civic responsibility and entitlement. In the early 2oth century, the public extended compulsory schooling into adolescence and provided opportunities for universal secondary education. In the second half of the 2oth century,  with the GI Bill and a succession of other measures, a widening sector of the
population gained access to higher education. As an historic force in education, early in the 21a century the lnternet is completing the democratization of education in a way that will make all educational opportunities open to all people at all times in all places.
As the internet completes the universalizing of educational opportunity, serious issues of public policy arise - issues of resources, of incentives and empowerment, of control and regulation, of assessment and accountability.
The following sections survey some of these issues.
Resources
Every major enhancement of educational opportunity has provided substantial personal and public benefit at increased cost. Since the mid-l9th century, enhanced access to education through compulsory elementary and secondary schooling and broadened admittance to higher education significantly raised expenditures for education, public and private. Societies around the world have unanimously judged the benefits of these educational efforts to be worth their substantial expense. There is no reason to expect the cost-benefit calculus with respect to digital technologies in education to be different. As it expands educational opportunity, the lnternet will force increases in educational expenditures.
But increased benefits to individuals, groups, organizations, and society at large will balance the expense. Traditionally, universal education was a wish, barely approximated by opportunities for large groups and cohorts - for instance, children aged 6 to 12, who received schooling for part of the day for part of the year. In principle the lnternet is greatly extending these historic achievements,
making educational experience accessible, not just to large cohorts, but to everyone, not only for significant periods, but all the time at any place – 24 hours a day, seven days a week, that is, "24/7" in current jargon. Further, the education afforded to all is greatly enriched. Traditionally, universal opportunity concentrated on elementary education, which had a very limited content. In principle, the lnternet now opens the full resources of higher education -the libraries, laboratories, and expertise of the culture - to all people in unprecedented ways. It makes digital participation in the cultural resources of every discipline and profession possible for anyone at any time from any place. But where will we get the resources to implement this added access? It is very difficult to estimate the costs, for the added access will change existing structures and add new ones. For 20 years, a demand for more technology for education has taken diverse forms. This demand continues and will grow as a recurring quest for new and increased expenditures, driven by the interaction of technical innovation, social need, and civic interest. Resources for open-ended innovation like this come from four main areas: individuals, philanthropy, government, and commerce.
  • Individuals Many of our society's cultural assets - textbooks, research papers, speeches and novels, not to mention images of great architecture and performing and fine art - need to be made available in a digital format. As people buy home computers and lnternet appliances they equip themselves to participate in the expansion of educational access. As more and more homes and individuals go online, they not only consume culture, they begin increasingly to contribute to it. All this greatly lowers the per capita costs of broadened educational participation. Numerous scholars, professionals, and individuals in the interested public openly contribute much lnternet content and create communities of critical exchange, all of which are significant elements of the lnternet as an educational force. Overall, individual commitments are necessary, but not sufficient, in generating the resources for the educational use of the Internet. As a necessary strategy in raising resources, voluntary action by individuals provides a significant base of effort. Were it to be the sufficient strategy, however, reliance on individual actions would exacerbate inequalities of educational opportunity by speeding those with many resources ahead while leaving lagging those with few.
  • Philanthropy. Philanthropic funds are playing a major role advancing the educational power of the Internet, most notably in helping to generate educational content for it, in creating resources adapted to populations with special needs and interests, and in helping to mobilize expertise needed to implement the effort. The World Wide Web exists because scholars at research labs and universities were able to design and implement powerful solutions to their problems of intellectual communication. Advanced information and communication technologies have become essential to the conduct of research and scholarship. Many of the philanthropic endowments and foundation grants driving the advancement of learning in our culture generate, as a secondary consequence, the digital content enabling the lnternet to become the locus of ubiquitous educational opportunity. The role of philanthropy in developing the educational uses of the lnternet is particularly important in higher education, which will increasingly become the provider of content for the entire structure of education, not only for specialized, advanced subjects. Philanthropy is unlikely, however, to provide a ubiquitous infrastructure for accessing all the content it helps to create.
  • Government. It is not clear whether public sources can generate the additional funds needed to implement the educational uses of the lnternet and digital technologies, especially the needed infrastructure. In the nation's schools, the average number of students per computer has been steadily decreasing, but that average masks extreme divergence between schools, and even within schools. Accidents of wealth, community interest, and leadership hustle are a few of the factors accounting for the divergent actualities within the average. Local governments are still expanding their commitment to increasing educational opportunity through the Internet. At the local level, for example, reasonably affluent communities frequently succeed in passing bond issues to equip schools and classrooms well. In some places, the lnternet also makes it possible to alter the politics of local educational funding by developing technology plans that serve a broad spectrum of  community needs -- schools, local hospitals, community and senior centers, local government, and small businesses. On the other hand, however, in many communities -- especially large urban school systems --the local ability to increase available funds is limited and the backlog of unmet demand for school construction and maintenance precludes generating much by way of technology expenditures. A few state governments have moderated local differences by building a consensus for special initiatives with technology. These are valuable, but at the state level, like the local, such initiatives may rely excessively on bond issues, as if expenditure for technology is a once-in-a-while matter akin to putting a new roof on the school. One time for all initiatives can set states up for long-term failure, for sound use of technology in education requires a new kind of substantial, on-going educational expenditure. Historically, schools in the United States have functioned as extremely stable institutions, with capital plants designed to last indefinitely and heavy annual staff expenditures. In fact, the budget of a school in 2000 differs little from the budget of a school in 1900. That's because most school budgets include virtually no internal investment for rationalizing and improving the schools' ways of doing business. This has to change. To realize the educational benefits of the Internet, schools need to restructure their budgets. They need to invest substantial resources in upgrading continuously their basic ways of doing business. To make full use of the Internet, schools need to develop an annual capital budget for continuously upgraded production tools and expanded training support. Mobilizing the resources to restructure educational budgets will not be easy. Schools cannot simply cut expenditures on plant or teachers and staff substantially, using the savings for new types of expenditure. The show must go on. Localities and states must inject expanding expenditures for equipment and content and lots of staff development into the existing mix. Over time, the new expenditures will have effects, not on the size of the old expenditures, but on the character of the educational operations that they support. Change requires added capital and support. Teachers want and deserve higher salaries; the public presses for reductions in class size, a longer school year, and higher learning standards; old buildings need refurbishing and new ones must be built - in short, traditional expenditures tend to grow. Yet localities and states have limited taxing powers. Change likewise requires assured capital and support. Implementing the lnternet requires pedagogical vision. If the most dynamic educators must devote inordinate effort to raising continuing funding and struggling to sustain innovative efforts, they will become mired in minutiae and loose their sense of vision. Liable to the flux of fashion and funding, localities and states have great difficulty sustaining long-term innovation. National programs can help provide capital and support that is both added and assured - up to a point. For instance, the federal government has stepped in over the past decade to help schools serving less advantaged students acquire lnternet connectivity and classroom technology through targeted programs. Provisions in the 1996 Telecommunications Act, for example, extended universal service concepts to include high-speed connectivity to schools and libraries in lower income communities (this is the so-called E-rate program). This program has greatly advanced the pace at which the lnternet is coming into effective use throughout elementary and secondary education. Combined with other programs in the Department of Commerce, the National Science Foundation, and the Department of Education, the E-rate program has also made possible a good deal of pedagogical experimentation with the lnternet in classrooms. But the role of the federal government in the elementary and secondary schools is too limited, relative to that of the states and localities, for federal programs to help across the board in restructuring school budgets to sustain continuous internal innovation. It is even less suited to underwriting  the implementation of educational access through the lnternet as a ubiquitous, "24/7" opportunity for all. Ubiquitous, "24/7"activity reaches into the confines of the private, everyday life of each person. The American ethos, one of limited government and a bill of rights protecting the autonomy of speech and assembly and much else from official reach, is very likely to resist the centralization of universal educational experience.
  • Commerce. Aside from the commercial provision of limited training programs, education in the United States has been almost entirely non-commercial. However, these days there are many signs that the broadening of access to education through the lnternet will bring much more commercial activity into education at all levels. Individuals, philanthropy, and government may not be able to do the whole job. Fully universalizing educational opportunity may require further resources, at a substantial scale.
For better and for worse, commerce is the great, untapped means for generating resources in education. Already, initial efforts to develop the lnternet in education through commercial initiatives are underway. First, non-commercial educational organizations - such as universities, libraries, and museums - are developing commercial initiatives to pursue their traditional missions with new media. Second, non-educational commercial organizations - such as publishers, new media start-ups, and large technology firms - are developing educational initiatives in pursuit of potentially profitable new business. Both types of initiative are likely to expand dynamically over coming decades and to intertwine, together and with non-commercial educators, in ways that are difficult to anticipate. Relatively soon, say by 2020 or so, these efforts at commercial education and at educational commerce are likely to have become a significant element in the provision of education opportunity in all developed societies. Substantial commercialization of education carries risks of historic loss, however, along with potential benefits. Modern educational systems have engaged in what Francis Bacon, the renaissance theorist of applied science, called the "advancement of learning," entailing both the creation and dissemination of knowledge. Modern educational systems have also served, well but imperfectly, to encourage criticism and to protect dissent. The danger of increasing commercialization in education is that it is not clear whether the pursuit of new knowledge or the enunciation of critical dissent have intrinsic value in the world of commerce. As the structure of education becomes increasingly commercial, policymakers may need to develop new ways to ensure that the emerging educational structures preserve and enhance the capacity to generate new knowledge and to bring criticism to  bear on the exercise of power. Otherwise, Internet-based education may turn ironic, becoming a deadening tool of orthodoxy, rather than a vital means of education for the public. Of all the issues likely to arise from the interaction of the lnternet with education, the role of commercial activity in the expansion of educational opportunity is likely to become the most deeply controversial. It is beginning to drive a wedge of basic disagreement into a broad, existing consensus about the range of activities appropriate in institutions of higher education and about the presence of profit-driven action in the elementary and secondary classroom.
Incentives and Empowerments
As the lnternet expands access to education, who does what, when, why, and how will also change. Expanded access to education does not simply mean that people will do exactly what they did before, only doing it longer and in more locations. Opportunities and pressures will both invite and push students, teachers, parents, academics, and the public to develop new pedagogical behaviors. With respect to these changes, policymakers need to consider potential patterns of empowerment and possible incentives to help key groups adapt.
  • Students As the lnternet expands access to education, it transfers a tremendous amount of educational initiative and control to students. First, the lnternet expands when and where students can find educational opportunities; what students could get previously only in classrooms they can now find at any time at any place. Second, the lnternet greatly increases the range of educational resources that students can use at will. In principle, the entire culture of humankind is online, open for use by any student, as he or she should see fit. The problem is that the operative rationale of modern education rests on principles of compulsion, from the idea of  compulsory schooling to reliance on the lesson and assignments, tests and grades. In contrast, the lnternet gives students of all ages, abilities, and interests an astounding range of choices. Where choices abound, compulsion may cease to work. Educational authorities may need to reexamine fundamentally the assumptions they make about motivation in designing programs for students.
  • Teachers As the lnternet expands educational access, teachers face an immediate task. They must learn how to incorporate advanced technologies into the work of the school. Then, they must also learn how to adapt the work of the school to a learning environment in which the traditional monopoly of the school on educational opportunity disappears. To enable them to cope with the first task, teachers and other professionals in the educational system are calling for increased professional development. It would be a mistake for policymakers to think that relatively simple training programs will satisfy this call. Schools are highly tuned institutions, with well-defined programs of activity and familiar, set roles for everyone working within them. There is little room for experimentation and adaptation in most schools' day-to-day routines. Patterns of practice that capitalize fully on the educational potentialities of the lnternet are very different from standard school practice, however. Standard professional development will not sustain a full transition from normal practice to an alternative pedagogy. The lnternet and the technical environment constantly develop and change. This continual change makes teachers' standard professional development expectations all wrong. Most teachers have come to expect that if they acquire a new skill or technique once well, they can use it, over and over again, this year and next, throughout their career. In contrast, computer technology requires dynamic principles of practice in which the agenda of work, the tools for it, and even the criteria of success and failure, constantly evolve and change. This means that teachers' professional development will have to become ubiquitous, constant, and available just in time and on-demand -just like the technology they are increasingly being called upon to use. Adapting the work of the school to an environment in which the school is just one of many distinct educational opportunities will alsorequire longer-term efforts which may diverge sharply from currently popular policy initiatives. Here teachers may have to reconcile sharply divergent visions about what they should try to accomplish. In most school districts around the country, current policies promulgating clear learning standards and mandating high-stakes testing aim to fine-tune the performance of existing schools. These policies do not necessarily perfect the program of the school for its usefulness in a world of expanded educational access. To prepare students to meet the standards and to perform well on high-stakes tests, many teachers feel they must restrict students' choices and authoritatively focus class attention on preparing for the tests. To prepare students to make the most of a wide range of autonomous choices, operative both in school and out, however, many teachers believe they should function instead as guides and mentors, helping students build their ability to sustain their own inquiry and learning. How the school and the teacher within it should function in a world of expanded educational access and choice is not clear. It will be important for policymakers to keep this issue uppermost in their minds, however, when developing new rules and regulations for education in the Information Age. As educators we will need to expand substantially the research on learning and teaching to provide a basis of knowledge for deciding such questions. Parents. Technology-expanded educational opportunity confronts parents with some new challenges. One expression of parental recognition that educational access is broadening is the home schooling movement. Some home schooling is driven by distaste for the values (or lack of them) that some parents feel is pervasive in schools. This sector of the home-schooling movement is generally not Internet-friendly. A growing component of the home-schooling movement, however, reflects the judgment by parents that their children could expend their pedagogical effort more productively by working at home, largely on the Internet. It is very likely that home schooling by such parents will not lead to "de-schooling" in any general sense, for there are many reasons parents and the public may choose to send children to schools, even though many other means of education are available to them. Many parents who themselves feel dissatisfied with their own educational efforts and opportunities may feel poorly qualified to guide their children's educational activities outside of schools. Even where access is equal, a "digital divide" in educational achievement may develop between children in homes where parents can help their children exploit expanded opportunities and children in homes where parents may not be so able. In fact, I foresee a substantial intergenerational need emerging. As expanded educational access to the lnternet becomes an actuality, whole families, children and adults together, will need shared learning centers to make full use of their complicated opportunities for a fuller education.
  • Academics Expanded access to education has great significance for scholarship and research. Traditionally, these fields have been out of reach for most people for research libraries and laboratories have historically been far too costly for everyone and anyone to enter, should they so wish. In universalizing educational opportunity, the lnternet brings these tools to any home and any classroom, for anyone to consult. Through the lnternet academics and professionals can begin to develop new audiences -- even, more radically, to broaden the community of peers. Some critics will say that lay people have no interest in the academics' work and that it is too demanding and confusing for ordinary folk. But the great challenge to self-governance in the 21* century inheres in the fact that all peoples have profound interests in the resolution of very complex and difficult problems, from science to economics to subtle questions of cultural value. Global warming, the global economy, peacekeeping, sustainable development - all these are complex matters in which all people have a substantial interest. Self governance requires people to participate in making decisions about such matters. With the Internet, people all over the world increasingly have both the means to deliberate on such issues and full access to the sources of knowledge relevant to them. Another crucial point involves the integrity of knowledge and expression. Historically, formal peer review in science, and the free clash of opinion and criticism in culture and public life, tended to ensure such integrity. By enabling a much wider sector to communicate ideas at will, the lnternet creates a significant challenge to academics, who now face an enlarged critical task. As the world of the Web proliferates, the responsibility to ensure the quality of information and ideas becomes ever more difficult. The lnternet makes the validation of content more difficult while involving more and more people in the active exchange of ideas. Peer review will involve broader criteria and a wider base of participation. The impetus may grow to de-emphasize intellectual validation as the basis for funding research and inquiry. In its place, funding may increasingly follow politically legislated mandates, based on the play of interests, not the discipline of reason, and the fashions of the marketplace and public opinion may compromise the quality of knowledge and culture. The lnternet poses a most difficult challenge: to preserve the research principles with which academics and scientists have created a reasonably progressive science and culture, while including everyone as participants in the work.
  • The Public Interests and needs drive public participation in the educational opportunities enabled by the Internet. It is a mistake to assume that relative to education, the public is a homogeneous mass. The lnternet has spread in spontaneous ways as diverse individuals and groups have perceived that it offers them interesting, meaningful possibilities. End users exert a great deal of control with  respect to the shape and content of the Internet. As a result, the lnternet is likely to develop a very interesting structure to its content.  Points of entry are likely to be very diverse; the aggregate uses that people engage in may nevertheless be highly shared and comprehensive. This structure may provide a way beyond the rather divisive debates that dominated the 80s and 90s about multiculturalism and the canon. Conflicts over multiculturalism and the canon have been difficult to solve because traditionally the structure of educational opportunity has been so limited -the point of entry and the aggregate were  essentially the same. In such a situation, people confronted either-or choices. If there were to be multiple points of engagement, the whole that each engaged would be different from others – there would be diversity with no unity. If there was to be a common canon, the entry point for engagement with it would be the same for all -there would be unity with no diversity. The extension of educational opportunity that the lnternet offers provides the opportunity for an education that fully achieves unity in diversity. The structure of cultural content that the lnternet enables is one in which each person is free to take their unique path into and through a common, shared aggregate of resources. This structure differs fundamentally from the structure of curricular debates in education up until the present time. It will take time to realize the possibilities inherent in this new structure in a double sense - it will take time to actualize the possibilities, and even more it will take time to become fully aware what they are.
Control and Regulation
The problems of control and regulation that are endemic to the lnternet impinge upon it s educational effectiveness. These problems arise in part because the lnternet blends activities together - in particular, commerce, entertainment, and education - creating significant cross-interference. Problems of control and regulation also arise because the lnternet greatly accentuates the tendency to disregard the structure of established jurisdictions, something that is already evident in modern communications and transportation. Paradoxically, the characteristics of the lnternet that make it such a powerful force for extending educational access also give rise  to these problems. The more the lnternet becomes the locus of education, the more pressing these issues will become. Consider two instances:
  • Freedom of speech In a world where anyone can communicate anything to anybody at any time, difficult issues of freedom of speech arise.  The Internet, designed to support interactive communication through the rigors of atomic war, may make these guarantees of free speech redundant, while creating new problems. Thus, policymakers could find it increasingly important to establish expectations of discretion and to implement procedures enabling people to exercise effective tact and prudence in lnternet exchanges that are intrinsically unfettered.
  • Copyrights and fair use As freedom of speech principles protect speakers or writers and their work against suppression, copyright protects the right to manufacture physical copies of intellectual work and to control the use of those copies. The copyright laws arose because, historically, copies took effort; they were costly to make and subject to progressive degradation, from one copy to the next. The right to make copies was an inherently limited right. Within the field of copyright, the traditions of fair use were developed to promote educational activity. "Fair use" is a more circumscribed, limited right under the copyright law to use parts of copyrighted works freely if they are intended strictly for instructional and scholarly purposes. Historically "fair use" served a valuable purpose because the technological limitations inherent in the physical processes of reproduction guaranteed that the loss to the value of copyrights through fair use would be marginal. These days, however, copies do not exist in the digital realm. Copies made on a copying machine degrade from one copy to the next. But there are no inherent limits on digital replicas - one replica is identical to the next and the creation of replicas requires neither significant cost nor effort. For all practical purposes, in the lnternet world "fair use" defines an infinite subset of an infinite set, each identical with every other. This situation raises significant difficulties for the regulation of intellectual property in general, and for the facilitation of educational use in particular. In a world in which any copy can give rise to innumerable identical replicas of itself, creators must choose between preserving the source in strict secrecy or opening it to unlimited duplication. This choice is frequently played out in the software industry, where companies maintaining source code for their products in strict secrecy compete with similar products based on open sources freely available to anyone. Unlike software source code, secrecy won't work for most domains of culture - science, art, literature, poetry, criticism, history, and the like. For these, the lnternet is a ubiquitous means of electronic publishing, of making materials public. Selling copies or the right to use copies many break down as a means of generating revenue from such intellectual property. In its place, there will be greater need to generate revenue by attaching advertising to creative work or creating public support for the creation of works to be placed directly into the public domain. 
 Other problems of control and regulation triggered or accentuated by the power of the lnternet to expand opportunities for education may become equally important. For instance, questions may develop about whether markets or whether public authorities should serve as the operative providers of important civic services. The lnternet makes commercial enterprise an increasingly effective means for raising the resources needed to extend unlimited educational opportunities to everyone. The power of commerce to raise resources derives from its clarity of purpose. Take return on capital: if the return is good, capital resources will accrue to an enterprise. So long as investors believe the returns will be high, commerce can generate substantial means for the pursuit of public goals. What happens should the expected returns drop?
Likewise, questions may develop about whether key lnternet domains should merge or remain distinct. New media marketers, for example, are touting the synthesis of entertainment and education under the heading "edutainment." Many will agree that education should be entertaining and learning fun. Many Americans also hold - or once did, at any rate –that entertainment should "elevate" and lift up the spirit. Yet the formula in entertainment today is to hold audiences by leaving their members unchanged, ready to return over and over again to repetitions of the same basic production. Education, in contrast, changes a person; the whole idea is to move from mastery of one thing to another, to develop, to grow, to mature. Can education and entertainment combine? Is "edutainment" really an oxymoron?
Finally, the any-time-anywhere learning that the lnternet fosters does not necessarily respect established boundaries and jurisdictions. Distance learning bursts apart the standard structures for accreditation that the academic world has come to use. For example, the French have become almost comical in their efforts to establish regulations ensuring parity for French as a global language on the Internet. What, given the anytimeanywhere characteristics of the Internet, is the locus and cultural character of the education that it is making so accessible to each and all? Who will guarantee quality and relevance? Who will provide vision and exert leadership? Towards what ends?
Assessment and Accountability
 As best they can, policy makers need to account for results. Therefore, the most important question becomes: will the benefits of "2417" educational opportunity for all people justify the costs? People, school systems and governments have committed the physical resources to make this opportunity available. They have empowered participants to adapt and change their ways of work to accommodate new ways of learning. They have coped with the strains engendered by historic change through sage strategies of control and regulation. Will they find the benefits worthy of the effort? This is the challenge of assessment and accountability.
 Where changes are incremental, assessment can rely on linear assumptions - each input should have a proportionate output. The assessment of educational innovation usually takes this form. Currently the public, press, and policy makers alike pay avid attention, whether or not they like the results, to measuring comparative academic performance in key subjects at key stages of the scholastic structure by scores on high-stakes tests. These measures track the outcome of effort within a given educational system, and they are political realities that demand attention. They are not, however, measures that will suffice to account for the benefits of the lnternet in education. The educational system as it exists cannot encompass the lnternet if we continue to rely on outdated measures. In extending educational access to unprecedented levels, the lnternet acts on the system, not within the system. It does not optimize; it transforms.
Transformative historical changes are much like changes of phase and they have significant latencies inherent in them. This creates two serious problems for effective assessment. First, standard measures may show no effects throughout a period of latency. Assessment programs using standard techniques to identify the effects of the lnternet in education may deceptively indicate that expensive efforts have no effect, weakening the rationale for investment in the efforts. Second, with transformative physical phenomena, observers usually know nearly as much about the altered state as they do about the former condition, and hence they have a reasonably good idea about how to test for the post-latency relationship. With transformative historical phenomena, people do not simply observe the transformation; they undergo it. As they undergo it, they have no way of knowing exactly what the post-latency state will be like. Hence, it is intrinsically difficult to develop and introduce new, post-latency assessment measures. But we must develop these measures. They are likely to involve indicators showing extreme diversity in the users of high-quality cultural resources on the lnternet and the degree to which the collections of great libraries and  useums are available and used at a distance. Pressure on formal educational programs to serve as gatekeepers and as sources of credentials may diminish. People may report participation in intellectual and cultural activities to be intrinsic goals, rather than means towards extrinsic purposes in higher proportions than now they might report. Increasing difficulty in trying to apply the old measures in situations where traditionally they once worked well, as patterns of behavior now slip away from established expectations, might indicate that transformative changes were taking hold of educational practice. Many familiar strategies of assessment rest on the assumption that one can predict what a good student should know as the result of an educational experience. That assumption becomes dubious in an educational environment in which the lnternet empowers students to interact with the whole culture. The very definition of accountability may change. Currently accountability aims at giving the public evidence that educational programs meet the purposes they are designed to serve. In a system in which each student can continuously select from and interact with the whole culture, assessment itself may become an operational resource, providing self-directing individuals with much more effective, immediate feedback, that helps them manage their work.
CONCLUSION
The lnternet makes a process of social and educational democratization possible. With it, societies can extend meaningful educational opportunities to all people at all places at all times. Such an achievement, if fulfilled, will not be the work of technology; it will be a profoundly human, social achievement. As such, it will take time and sustained effort. In education, it is especially difficult to concentrate on truly long-term policy - people rightly feel that the educational interests of children, here and now, must not get sacrificed in pursuit of improvements that will help children growing up in a far off future. When policy becomes too longterm, it unfairly sacrifices today for the betterment of tomorrow. We can  view this problem differently, however. Here and now, the most important idea, which can become real for everyone, is that education at its best is continually a work in progress. Existing schools impress people, especially the young, as fixed and stable givens, places of predictable routine. Education should not comprise a fixed program, good or bad, that people do to the young, the aspiring, the perplexed. Education is properly a shared, unfolding, open effort. Insofar as educational programs appear monolithic and unchanging, they are at their core miseducational, for they communicate a profound mistruth to their participants, that good education consists in fixed and bounded programs. Human possibilities are unlimited. Educational activity should exemplify that truth. Educational institutions themselves should engage in an unending quest to reach beyond  established achievements, not only at the cutting edge of research, but pervasively throughout their work. Educational arrangements must communicate to all the boundlessness of possibility - here and now - by committing to a vision of continuous change that leads far beyond what anyone can reasonably expect to achieve in the finite future.

Tuesday, December 29, 2009

Hard Disk

Disks are the most commonly used type of storage. There is a wide variety of different disk types, including many sizes and formats of floppy disks, hard disks, optical disks, CD-ROMs (Compact Disc Read-Only Memory), and removable hard disks (such as Syquest).

In general, all sorts of disk storage share certain common elements. On all disks, physical differences in the surface of the disk are used to represent data. On  floppy and hard disks, magnetism is used to encode data. On CD-ROM and optical disks, variations in how the disk surface reflects light are used to encode data. Here we discass only the hard disks.



Disks arrange information into concentric rings called tracks. Tracks are divided into pie-like slices called sectors. Some disks can be written to only on one side; others can be written to on both sides. A read/write head can be positioned over any track, and data is read (or written) as the sectors pass by.

Hard drives, or fixed disks, are a type of storage device that provide fast access to large amounts of storage in a small, reasonably reliable physical package. Without them, most modern computing applications would be impossible. Hard disks are often composed of multiple disks. A cylinder consists of a track on the top side of the top-most disk, and all of the tracks beneath it, as shown in Figure. A cylinder represents all of the data that the read/write heads can access when they are in a certain position. (There is a separate read/write head for each side of each disk, but they all move together.)


Hard drives have been designed to meet users’ needs for speed and capacity. With the maturation of the technology, designers now add reliability to, and reduce the cost of, the design process. This constant redesign process has produced better drives, in many different types. However, even with differences,
almost all hard drives operate the same way: data is stored as locations of magnetic flux, or change, on a disk of specially coated aluminum or glass. Hard disks can have one or more of these platters or disks. The information is read or written with a head, or small magnet, that floats on a cushion of air over the platter. The platter spins at a high rate, generally 5,400 or 7,200 revolutions per minute (rpm). The heads are moved across the platter by one of two technologies: older designs used a motor, called a stepper motor, that moved only in pre-defined increments, or steps. Newer designs use a voice-coil, similar to an audio speaker, to move the heads more precisely over the platter.

Writing Data to the Hard Disk

Hard disks spin at very fast speeds, and the read/write heads hover over the platters, very close to the surface so that they can read or write data. The platters are made of a rigid material, such as aluminum, that is coated with a magnetic material. To write data, the computer positions the head in a particular track. When the appropriate sector passes by, pulses of electricity are sent through a coil of wire in the head. This creates an electromagnetic field, which aligns magnetic particles on the disk surface. By alternating the flow of the current to the head, ones and zeroes can be encoded magnetically.
The data is encoded, or written, in circular tracks as the head floats over the rotating platter. Each platter has its own read/write head. The newer voice-coil designs allow cylinders to be written closer together so more data can be fit onto the same-sized platter


Reading Data from the Hard Disk

To read data, the computer positions the head over the appropriate track. When the sector passes by, the magnetic particles on the disk create an electrical current in the head through a phenomenon known as inductance. In the head, the alternating patterns of magnetism on the disk translate into alternating flows of electrical current, which can be translated into ones and zeroes.

Avoiding Head Crash

You should never transport or jar a hard disk that is spinning, because you can easily cause a head crash. If the read/write heads bang against the surface of the disk, you might damage that part of the disk, and possibly the read/write heads as well. Most hard-disk drives automatically park over an unused section of the disk when the computer is switched off. Hard-disk drives are tightly sealed to prevent dust and other particles from entering the drive. A single dust particle is likely to be larger than the gap between the
head and the disk platter. With the platter spinning, dust acts like sandpaper on the surface of the disk. For this reason, you should never break the seal on a hard-disk drive.






An Introduction to Microcontroller

It was year 1969, and a team of Japanese engineers from the BUSICOM company arrived to United States with a request that a few integrated circuits for calculators be made using their projects. The proposition was set to INTEL, and Marcian Hoff was responsible for the project. Since he was the one who has had experience in working with a computer (PC) PDP8, it occured to him to suggest a fundamentally different solution instead of the suggested construction. This solution presumed that the function of the integrated circuit is determined by a program stored in it. That meant that configuration would be more simple, but that it would require far more memory than the project that was proposed by Japanese engineers would require. After a while, though Japanese engineers tried finding an easier solution, Marcian's idea won, and the first microprocessor was born. In transforming an idea into a ready made product , Frederico Faggin was a major help to INTEL. He transferred to INTEL, and in only 9 months had succeeded in making a product from its first conception. INTEL obtained the rights to sell this integral block in 1971. First, they bought the license from the BUSICOM company who had no idea what treasure they had. During that year, there appeared on the market a microprocessor called 4004. That was the first 4-bit microprocessor with the speed of 6 000 operations per second. Not long after that, American company CTC requested from INTEL and Texas Instruments to make an 8-bit microprocessor for use in terminals. Even though CTC gave up this idea in the end, Intel and Texas Instruments kept working on the microprocessor and in April of 1972, first 8-bit microprocessor appeard on the market under a name 8008. It was able to address 16Kb of memory, and it had 45 instructions and the speed of 300 000 operations per second. That microprocessor was the predecessor of all today's microprocessors. Intel kept their developments up in April of 1974, and they put on the market the 8-bit processor under a name 8080 which was able to address 64Kb of memory, and which had 75 instructions, and the price began at $360.

In another American company Motorola, they realized quickly what was happening, so they put out on the market an 8-bit microprocessor 6800. Chief constructor was Chuck Peddle, and along with the processor itself, Motorola was the first company to make other peripherals such as 6820 and 6850. At that time many companies recognized greater importance of microprocessors and began their own developments. Chuck Peddle leaved Motorola to join MOS Technology and kept working intensively on developing microprocessors.

At the WESCON exhibit in United States in 1975, a critical event took place in the history of microprocessors. The MOS Technology announced it was marketing microprocessors 6501 and 6502 at $25 each, which buyers could purchase immediately. This was so sensational that many thought it was some kind of a scam, considering that competitors were selling 8080 and 6800 at $179 each. As an answer to its competitor, both Intel and Motorola lowered their prices on the first day of the exhibit down to $69.95 per microprocessor. Motorola quickly brought suit against MOS Technology and Chuck Peddle for copying the protected 6800. MOS Technology stopped making 6501, but kept producing 6502. The 6502 was a 8-bit microprocessor with 56 instructions and a capability of directly addressing 64Kb of memory. Due to low cost , 6502 becomes very popular, so it was installed into computers such as: KIM-1, Apple I, Apple II, Atari, Comodore, Acorn, Oric, Galeb, Orao, Ultra, and many others. Soon appeared several makers of 6502 (Rockwell, Sznertek, GTE, NCR, Ricoh, and Comodore takes over MOS Technology) which was at the time of its prosperity sold at a rate of 15 million processors a year!

Others were not giving up though. Frederico Faggin leaves Intel, and starts his own Zilog Inc.
In 1976 Zilog announced the Z80. During the making of this microprocessor, Faggin made a pivotal decision. Knowing that a great deal of programs have been already developed for 8080, Faggin realized that many would stay faithful to that microprocessor because of great expenditure which redoing of all of the programs would result in. Thus he decided that a new processor had to be compatible with 8080, or that it had to be capable of performing all of the programs which had already been written for 8080. Beside these characteristics, many new ones have been added, so that Z80 was a very powerful microprocessor in its time. It was able to address directly 64 Kb of memory, it had 176 instructions, a large number of registers, a built in option for refreshing the dynamic RAM memory, single-supply, greater speed of work etc. Z80 was a great success and everybody converted from 8080 to Z80. It could be said that Z80 was without a doubt commercially most successful 8-bit microprocessor of that time. Besides Zilog, other new manufacturers like Mostek, NEC, SHARP, and SGS also appeared. Z80 was the heart of many computers like Spectrum, Partner, TRS703, Z-3 .

In 1976, Intel came up with an improved version of 8-bit microprocessor named 8085. However, Z80 was so much better that Intel soon lost the battle. Altough a few more processors appeared on the market (6809, 2650, SC/MP etc.), everything was actually already decided. There weren't any more great improvements to make manufacturers convert to something new, so 6502 and Z80 along with 6800 remained as main representatives of the 8-bit microprocessors of that time.

Microcontrollers versus Microprocessors

Microcontroller differs from a microprocessor in many ways. First and the most important is its functionality. In order for a microprocessor to be used, other components such as memory, or components for receiving and sending data must be added to it. In short that means that microprocessor is the very heart of the computer. On the other hand, microcontroller is designed to be all of that in one. No other external components are needed for its application because all necessary peripherals are already built into it. Thus, we save the time and space needed to construct devices.

1 Memory unit

Memory is part of the microcontroller whose function is to store data.
The easiest way to explain it is to describe it as one big closet with lots of drawers. If we suppose that we marked the drawers in such a way that they can not be confused, any of their contents will then be easily accessible. It is enough to know the designation of the drawer and so its contents will be known to us for sure.


Memory components are exactly like that. For a certain input we get the contents of a certain addressed memory location and that's all. Two new concepts are brought to us: addressing and memory location. Memory consists of all memory locations, and addressing is nothing but selecting one of them. This means that we need to select the desired memory location on one hand, and on the other hand we need to wait for the contents of that location. Beside reading from a memory location, memory must also provide for writing onto it. This is done by supplying an additional line called control line. We will designate this line as R/W (read/write). Control line is used in the following way: if r/w=1, reading is done, and if opposite is true then writing is done on the memory location. Memory is the first element, and we need a few operation of our microcontroller .

2 Central Processing Unit 

Let add 3 more memory locations to a specific block that will have a built in capability to multiply, divide, subtract, and move its contents from one memory location onto another. The part we just added in is called "central processing unit" (CPU). Its memory locations are called registers.



Registers are therefore memory locations whose role is to help with performing various mathematical operations or any other operations with data wherever data can be found. Look at the current situation. We have two independent entities (memory and CPU) which are interconnected, and thus any exchange of data is hindered, as well as its functionality. If, for example, we wish to add the contents of two memory locations and return the result again back to memory, we would need a connection between memory and CPU. Simply stated, we must have some "way" through data goes from one block to another.

3 Bus

That "way" is called "bus". Physically, it represents a group of 8, 16, or more wires
There are two types of buses: address and data bus. The first one consists of as many lines as the amount of memory we wish to address, and the other one is as wide as data, in our case 8 bits or the connection line. First one serves to transmit address from CPU memory, and the second to connect all blocks inside the microcontroller.

As far as functionality, the situation has improved, but a new problem has also appeared: we have a unit that's capable of working by itself, but which does not have any contact with the outside world, or with us! In order to remove this deficiency, let's add a block which contains several memory locations whose one end is connected to the data bus, and the other has connection with the output lines on the microcontroller which can be seen as pins on the electronic component.

4 Input-output unit

Those locations we've just added are called "ports". There are several types of ports : input, output or bidiectional ports. When working with ports, first of all it is necessary to choose which port we need to work with, and then to send data to, or take it from the port.


When working with it the port acts like a memory location. Something is simply being written into or read from it, and it could be noticed on the pins of the microcontroller.
5 Serial communication
Beside stated above we've added to the already existing unit the possibility of communication with an outside world. However, this way of communicating has its drawbacks. One of the basic drawbacks is the number of lines which need to be used in order to transfer data. What if it is being transferred to a distance of several kilometers? The number of lines times number of kilometers doesn't promise the economy of the project. It leaves us having to reduce the number of lines in such a way that we don't lessen its functionality. Suppose we are working with three lines only, and that one line is used for sending data, other for receiving, and the third one is used as a reference line for both the input and the output side. In order for this to work, we need to set the rules of exchange of data. These rules are called protocol. Protocol is therefore defined in advance so there wouldn't be any misunderstanding between the sides that are communicating with each other. For example, if one man is speaking in French, and the other in English, it is highly unlikely that they will quickly and effectively understand each other. Let's suppose we have the following protocol. The logical unit "1" is set up on the transmitting line until transfer begins. Once the transfer starts, we lower the transmission line to logical "0" for a period of time (which we will designate as T), so the receiving side will know that it is receiving data, and so it will activate its mechanism for reception. Let's go back now to the transmission side and start putting logic zeros and ones onto the transmitter line in the order from a bit of the lowest value to a bit of the highest value. Let each bit stay on line for a time period which is equal to T, and in the end, or after the 8th bit, let us bring the logical unit "1" back on the line which will mark the end of the transmission of one data. The protocol we've just described is called in professional literature NRZ (Non-Return to Zero).

As we have separate lines for receiving and sending, it is possible to receive and send data (info.) at the same time. So called full-duplex mode block which enables this way of communication is called a serial communication block. Unlike the parallel transmission, data moves here bit by bit, or in a series of bits what defines the term serial communication comes from. After the reception of data we need to read it from the receiving location and store it in memory as opposed to sending where the process is reversed. Data goes from memory through the bus to the sending location, and then to the receiving unit according to the protocol.

6 Timer unit

Since we have the serial communication explained, we can receive, send and process data.


However, in order to utilize it in industry we need a few additionally blocks. One of those is the timer block which is significant to us because it can give us information about time, duration, protocol etc. The basic unit of the timer is a free-run counter which is in fact a register whose numeric value increments by one in even intervals, so that by taking its value during periods T1 and T2 and on the basis of their difference we can determine how much time has elapsed. This is a very important part of the microcontroller whose understanding requires most of our time.

7 Watchdog

One more thing is requiring our attention is a flawless functioning of the microcontroller
during its run-time. Suppose that as a result of some interference (which often does occur in industry) our microcontroller stops executing the program, or worse, it starts working incorrectly.



Of course, when this happens with a computer, we simply reset it and it will keep working. However, there is no reset button we can push on the microcontroller and thus solve our problem. To overcome this obstacle, we need to introduce one more block called watchdog. This block is in fact another free-run counter where our program needs to write a zero in every time it executes correctly. In case that program gets "stuck", zero will not be written in, and counter alone will reset the microcontroller upon achieving its maximum value. This will result in executing the program again, and correctly this time around. That is an important element of every program to be reliable without man's supervision.

8 Analog to Digital Converter

As the peripheral signals usually are substantially different from the ones that microcontroller can understand (zero and one), they have to be converted into a pattern which can be comprehended by a microcontroller. This task is performed by a block for analog to digital conversion or by an ADC. This block is responsible for converting an information about some analog value to a binary number and for follow it through to a CPU block so that CPU block can further process it.


Finnaly, the microcontroller is now completed, and all we need to do now is to assemble it into an electronic component where it will access inner blocks through the outside pins. The picture below shows what a microcontroller looks like inside.

Physical configuration of the interior of a microcontroller 

Thin lines which lead from the center towards the sides of the microcontroller represent wires connecting inner blocks with the pins on the housing of the microcontroller so called bonding lines. Chart on the following page represents the center section of a microcontroller


Microcontroller outline with its basic elements and internal connections
For a real application, a microcontroller alone is not enough. Beside a microcontroller, we need a program that would be executed, and a few more elements which make up a interface logic towards the elements of regulation

9 Program

Program writing is a special field of work with microcontrollers and is called "programming". Try to write a small program in a language that we will make up ourselves first and then would be understood by anyone.

START
REGISTER1=MEMORY LOCATION_A
REGISTER2=MEMORY LOCATION_B
PORTA=REGISTER1 + REGISTER2


END

The program adds the contents of two memory locations, and views their sum on port A. The first line of the program stands for moving the contents of memory location "A" into one of the registers of central processing unit. As we need the other data as well, we will also move it into the other register of the central processing unit. The next instruction instructs the central processing unit to add the contents of those two registers and send a result to port A, so that sum of that addition would be visible to the outside world. For a more complex problem, program that works on its solution will be bigger.
Programming can be done in several languages such as Assembler, C and Basic which are most commonly used languages. Assembler belongs to lower level languages that are programmed slowly, but take up the least amount of space in memory and gives the best results where the speed of program execution is concerned. As it is the most commonly used language in programming microcontrollers it will be discussed in a later chapter. Programs in C language are easier to be written, easier to be understood, but are slower in executing from assembler programs. Basic is the easiest one to learn, and its instructions are nearest a man's way of reasoning, but like C programming language it is also slower than assembler. In any case, before you make up your mind about one of these languages you need to consider carefully the demands for execution speed, for the size of memory and for the amount of time available for its assembly.
After the program is written, we would install the microcontroller into a device and run it. In order to do this we need to add a few more external components necessary for its work. First we must give life to a microcontroller by connecting it to a power supply (power needed for operation of all electronic instruments) and oscillator whose role is similar to the role that heart plays in a human body. Based on its clocks microcontroller executes instructions of a program. As it receives supply microcontroller will perform a small check up on itself, look up the beginning of the program and start executing it. How the device will work depends on many parameters, the most important of which is the skillfulness of the developer of hardware, and on programmer's expertise in getting the maximum out of the device with his program.

(PIC microcontrollers, for beginners.    author: Nebojsa Matic Chapter 1)