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Since computer terminology can often be one of the biggest stumbling blocks to understanding the world of personal computers,I've tried to make things a bit easier by defining new terms at the beginning of the chapter in they first appear

Showing posts with label TYPES OF MEMORY STORED WITHIN A SYSTEM. Show all posts
Showing posts with label TYPES OF MEMORY STORED WITHIN A SYSTEM. Show all posts

Sunday, 29 January 2012

TYPES OF MEMORY STORED WITHIN A SYSTEM


There are two types of memory stored within a system:
1. Read Only Memory (ROM)
2. Random Access Memory (RAM)
Read Only Memory is permanently imprinted in your computer when you get it. It is called ROM because it is meant to be read only by the computer itself. The person operating the computer has no control over it. The computer uses this memory to tell itself how to start up when you turn it on. Read Only Memory processes the electrical data flow from the keyboard to the CPU and from the CPU to the video display screen or to any other peripheral equipment you have attached, such as a printer. The decoders that translate numbers and characters into binary information that the computer understands are found in ROM. These programs are called firmware, or nonvolatile, because they are always there, and are not erased or destroyed when the power is turned off.
The other memory a system works with is called, Random Access Memory (RAM). This is what some people also call Read/ Write Memory, and is considered volatile because the information stored here is lost whenever the computer is shut off, or when power is lost. Random Access Memory is controlled by the person working with a system, and is where the instructions and information needed to get a job done are temporarily stored. Personal computer systems are often described by the amount of short- term (RAM) memory available (i.e., 64K, 256K, 640K). Most software programs also list the amount of memory they require to be stored in RAM. Most systems allow the user to increase the amount of memory available by installing additional single memory chips or expansion boards containing multiple chips. Even with these, however, there are finite limits to the amount of memory a personal computer has to work with. This is one reason why it is important to decide what kinds of work you would like to perform on a personal computer and the software most appropriate for accomplishing those tasks, before you purchase the system. This allows a computer to be configured to meet anticipated uses and eliminates the problem that a lot of people encounter of trying to install a software program that requires more memory than their system has available. In these situations the only recourse is to purchase and install more memory. A person using a computer comes in contact with all of its working parts. When a system is first turned on, the operating system takes over and makes sure everything under its control is functioning properly. Information is put into the system, where it is stored in memory according to an address code assigned by the computer, as seen in Figure 14. When the program (or list of instructions) is loaded, data are taken from the memory. Following the program instructions, the

FIGURE 14.  The flow of information processing. Illustration by Gina Bean. Data are then worked on in the Arithmetic Logic Unit (ALU). When all the instructions have been carried out, the information is returned to memory or to an output device.
Output can be delivered through any of several sources:
.Video Monitor (CRT)
.Printer
.Voice synthesizer
.Modem for transferring information over telephone lines
.Storage device (diskette, hard disk, etc.)



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Friday, 27 January 2012

Supercomputers


Specially designed systems (usually several computers tied together). Used primarily in government or research. These are the most expensive and largest systems available, and they possess tremendous computing power. The cost of operating and maintaining them makes them prohibitive hit most organizations. One example of a supercomputer Is 11w one operated by the National Security Agency. Built at a cost 
 
 FIGURE 9. Cray Supercomputer shown here with designer Seymour Cray of Cray Research, Inc.
Of approximately $15 million, it is rumored to be capable of 150 to 200 million calculations per second, and has a memory capable of transferring  320 million words per second. This system is reported to be so powerful that the heat is generates would melt is down were it not for a specially designed cooling system.*
At present, there are some 150 supercomputers (similar to that in Figure 9), in operation around the world, with most located in the United States. The latest models have a memory capacity  some two billion bytes and processing speeds 40,000 to 50,000 times faster than a personal computer. Tasks that once took a year to accomplish on a second-generation computer can be done in about a second with a supercomputer.* Mainframes. These are the large machines that come to mind when most people think of computers. Costing hundreds of thousands of dollars, and requiring specially built facilities and large supporting staffs of operators, programmers, and analysts, they are designed to handle large volumes of work or complex calculations.
Minicomputer. Smaller than a mainframe and generally costing under $200,000, these systems are ideally suited for a medium- sized organization. They require smaller facilities and less staff than the mainframes, but have enough, power to process a wide range of commercial or scientific jobs.
Microcomputer. This is where the personal computer fits in. Designed to sit on the top of a desk, and within the financial reach of most organizations and many individuals, these systems represent the latest evolutionary stage. While not yet in the same league as their larger cousins, they can easily match or outperform the computing power of their first- and second- generation ancestors.
Lap-Top Computers. An offshoot of the personal computer, these small systems (many are complete with printer and liquid crystal displays) can offer the same type of power and functionality as a desktop model. Designed for portability, they can travel inside an attach case as seen in Figure 10, and can be used just about anywhere.
While personal computers can trace their lineage back several centuries (see Exhibit 5), they are a relatively new phenomenon. The personal computer revolution really got underway in 1969 with the invention of the Intel 4004 microprocessor, which contained 2250 transistors on a single microchip. At first, these were available only to large manufacturers, but in 1971 Intel decided to clear out its stocks by offering the 4004 microprocessor for
*Philip Elmer-Dewitt, “A Sleek, Super powered Machine,” Time (June 17, 1985). 53.

















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THE WORLD OF PERSONAL COMPUTERS



                               Clearly, the machine no longer belonged to its makers.
            
 TRACY KIDDER,
                                                                                                            
  The Soul of a New Machine

Computers have been around a lot longer than most of us would like to believe. As a matter of fact, the computer’s lineage can be traced back to 1642 when Blaise Pascal, a French mathematical genius, invented the first real calculating machine. Pascal’s machine used a combination of rotating wheels and gears to perform simple problems of addition and subtraction.
In 1833 Charles Babbage, an English inventor, designed the great-grandfather of modern computers with the introduction of his analytical engine a forerunner of which is pictured below in Figure 3. The engine was composed of five parts:
(1) A calculating unit (the mill),
(2) The store (memory),
(3) An input device,
(4) A control section, and
(5) A printer, the system was driven by punched cards that fed the basic information into the engine, where it could be processed. Babbage also fathered the basic principles on which the first adding machine was constructed.
In 1842, Lady Augusta Ada Lovelace, a friend of Babbage, wrote the first computer documentation in her paper ‘‘Observations of Mr. Babbage Analytical Machine.' A mathematical prodigy,

FIGURE 3.  Babbage’s differential machine, a forerunner of his analytical engine, marked a major step towards the future development of computers. Smithsonian Institution photo number 53190.
Ada established herself as the world’s first computer programmer and provided the software for Babbage’s engine. In recognition of her contributions, the U.S. Department of Defense named its so-called super language after her and Ada became a registered trademark of the U.S. government. The 1840s saw the publication of several papers and theses by the English mathematician George Boole. Boole’s theories detailed how logical problems can be solved like algebraic equations. Boolean logic set the stage for the advent of computer science. In 1890, the first electronic calculating machine was invented Known as the Hollerith tabulator, it used punched cards for the first time. The United States used the Hollerith tabulator (Figure 4) to compute the census, and completed the job in a mere six weeks. Up to that time, it had taken as long as 10 years to prepare the census calculations. The era of modern computing began in 1925 at the Massachusetts Institute of Technology. There, a team of engineers led by Vannevar Bush developed a large-scale analog calculator since it was capable of storing number values electronically; this is considered the advent of-all that was to follow.

Figure 4 .Hollerith's tabulator provided a taste of future computing power when first used in figuring the results at the 1890 United States Census. Smithsonian Institution photo number 64563.
The 1930s and 1940s saw a number of advances in computer development, with the development of two of the more famous systems: ENIAC (electronic numerical integrator and computer) in the United States, and Colossus, the world’s first electronic computer, in England. Colossus was placed into operation to decipher the signals of Enigma, the German code machine. Colossus was credited with breaking Enigma’s code, which provided the necessary information to help the allies win the war. Colossus was SO secret that it was dismantled at the end of the war and only one piece is known to survive today. At the end of 1945 ENIAC arrived on the scene and solved its first problem in December of that year. The problem dealt with the hydrogen bomb, and is still considered a classified secret. The ENIAC, a portion of which is shown in Figure 5, was composed of 40 panels, each two feet wide and four feet deep, and housed some 18,000 vacuum tubes. It was capable of handling more than

FIGURE 5. ENIAC, one of the world’s first computers. Courtesy of International Business Machines.
One problem, although it had to be manually programmed by resetting switches, a process that could take up to two days.
Perhaps as a harbinger of things to come, ENIAC was obsolete almost as soon as it was running. A newer generation of stored program computers, which could be programmed electronically (instead of by recabling everything by hand), arrived in 1946 and quickly replaced ENIAC. For all its importance as one of the world’s first electronic computers, ENIAC had neither the power nor the speed of many of today’s hand-held calculators.
At that time, however, the sheer number of vacuum tubes needed to operate these early computers limited their use. Vacuum tubes were always burning out, so only short programs could be run. These machines literally filled entire rooms and were programmed at very low levels, often by a person setting and resetting row after row of switches and by recabling the system. Little wonder that a post-war government report saw little use for such machines and predicted that there might be a need for no more than three or four in the entire country. That might have been true, if the vacuum tube had remained the standard electronic core of a computer. The invention of the transistor in 1947 by Bell Laboratory scientists superseded the vacuum tube. The transistor was compact, used low voltages, and small amounts of power. It freed computers from the need be vacuum tubes and revolutionized the computer industry, setting the stage for today’s smaller computer systems. In 1951, the world’s first commercial computer, UNIVAC (Figure 6), was delivered to the Census Bureau. The UNIVAC set the trends for years to come and laid down standards that are followed even today. The original UNIVAC still blinks away at the Smithsonian Institute. Throughout the 1950s, 1960s, and 1970s, improvements in the construction of transistors opened new doors for computer man- manufacturing. The first transistors gave way to the integrated circuit, in which a number of transistors and the wiring that connects them were constructed in a single piece. Integrated circuits, turn, led to the development of wafer—thin silicon chips on which thousands of transistors can be packed into an area about one quarter of an inch square as in Fig7.


FIGURE 6. UNIVAC, the world’s first commercial computer. Smithsonian Institution photo number 72-2616.
The development of transistors and microchips led to the creation of bigger and more powerful computers. It also allowed smaller and cheaper machines to come into existence... In short, these developments led to the evolution of several distinct families of computers, as well as to a continuing decrease in the cost of computing power. In fact, since the mid-1970s, the cost of computing power has dropped by an average of 50 percent per year. A comparison of computing power then and now can be seen in Figure 8.



FIGURE 7 .  Line drawing of a microchip. Illustration by Gina Bean .




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