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Computers and How They Work
Written by Roderick Hames Spring 2009 Alton C. Crews Middle School
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Why is it important to know how a computer works? Easy, if you don't, it will be hard to control. Computers were never built to control us even though that is how it appears. Their creation was just another tool God gave man to use to benefit society. What can you do to learn more about computers? I have an easy answer. Just read, and use computers more. They are not that hard and with time you too can become the master over this tool.
Computers, today are small, fast, reliable, and extremely useful. Back in 1977 that really was not the case. However, they both operated in basically the same way. They both receive data, stored data, processed data, and then output data similar the the way our own brain functions. This article deals with those 4 functions: Memory, Processing, Input, and Output.
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Memory
Lets look at computer memory first. The function of storage in a computer comes in many different sizes, types and shapes. However there are two basic categories: short-term and long-term. A typical computer contains numerous types of memory including RAM, ROM, virtual, cache, and various long-term storage devices. Each type of computer memory serves a specific function and purpose.
Computer memory is measured in bytes. A single byte is made up of a series of 1's and 0's normally traveling in pairs of eight. These eight 0's and 1's are the way the computer communicates and stores information. With each keystroke or character a byte of memory is used. In another article you will learn more about bits and how the computer thinks.

Measuring Memory
Term/Byte Abbreviation Value
Kilo K, KB 1,024 bytes
Mega M, MB, Meg 1,048,576 bytes (Million)
Giga G, GB, Giga 1,073,741,824 bytes (Billion)
Tera T, TB, Tera 1,099,511,628,000 bytes (Trillion)
Here is another way of looking at the measurement of memory:
Measuring Bytes
8 bits = 1 byte
1000 bytes = 1 kilobyte
1000 kilobytes = 1 megabyte
1000 megabytes = 1 gigabyte
1000 gigabytes = 1 terabyte

ROM
ROM, or read-only memory is permanent, long-term, nonvolatile memory. Nonvolatile means is doesn't disappear when the computer is shut off. It also can not be erased or changed in anyway. However there are types of ROM called PROM that can be altered. The P stands for programmable. ROM's purpose is to store the basic input/output system (BIOS) that controls the start-up, or boot process.
RAM
RAM, or random-access memory unlike ROM works only when the computer is turned on. This memory is vital to the computer because it controls the moment by moment processes of the computer. The first thing that goes into RAM is the OS (operating system) which is most cases is Windows 95. Next for the RAM might be a game, or the Internet browser, or some type of software that you want to use.
Early personal computer only needed about 64K of RAM. Today that number is drastically higher. With photos, sounds, and even movies going into RAM, the amount need is now in the millions. The computer I am currently using has 80 MB or 80,000K of RAM.
Multitasking has put more demand on RAM in the past few years. Multitasking is the ability to run more than one program at the same time. For instance, many people like to run Netscape Communicator along with their word processing software. This means you need lots of RAM to hold both programs.
Other types of temporary memory are cache (pronounced "cash") and virtual memory. Both of these types of memory supplement the computer's primary RAM and perform the same function as RAM.
Storage Devices:
RAM and ROM may be very important parts of the computer; however, without storage devices like hard drives and disk drives your computer would not be near as useful.
Here are the most common forms of Storage Devices found on your home computer:

Thumb Drive or Memory Stick Hard disk (drive) or HD
A device that in 1998 IBM introduced and has caught on very quickly as a great portable storage device. It quickly replaced the floppy disk. This small device is extremely reliable and fits in the USB port on your computer. It come in sizes ranging from 1 GB to 64 GB in size. A stack of round metal platters called disks encased in a metal air tight shell. They commonly range in sizes from 60 to 500 gigabytes (1000MB=1GB). The hard drive's function is to store all the files, and software the computer will ever use. Any file or software program used by RAM most likely will come from the disk drive.
CD-ROM (Compact disk, read-only memory) DVD-ROM (digital video disk, read-only memory)
CD's function much like hard drive in that they store large amounts of memory. What separates them is their mobility and optical storage technology. Their storage capacity is also very limited compared to hard drives. The can only hold up to approximately 650 MB of information. The other big difference is that you have to have a special drive to write to CD's. Otherwise they can only be read from. DVD's are similar to CD in that they are written and read by laser. Hard drives use magnetic currents store data. However CD's and DVD's use light (laser) to write and read data on a disk. These long and short pits are then stored or etched on the surface of the disk. They can only be read by laser technology. The new DVD technology increased the amount of memory a regular CD can hold. DVD's can range in sizes from 4.34GB (1000MB=1GB) to 7.95GB.

Processing
If someone had to find the brains of the computer they would most certainly say its the microprocessor. The microprocessor is often referred to as the CPU (Central processing unit). The microprocessor is a chip the size of a postage stamp. The processor is the one part of the computer that is most important to the computer. The microprocessor controls how data is sorted and directs the flow of data.
To a great extent a computer is defined by the power of its microprocessor. Chips with higher processing speed and more recent design offer the greatest performance and access to new technologies. Most microprocessors made for PCs are made by Intel or by companies that clone Intel chips, such as Advanced Micro Devices (AMD) and Cyrix.
The early Intel chip came in models called 286, 386, and 486. The 586 chip was given the name Pentium. The series of Pentiums were given the following names: Pentium Pro, Pentium with MMX, and Pentium II. The newer processors hold more transistors and thus more computing power on a single chip.
Microprocessor
Processor No. of Transistors Bus Width
80286 134,000 16 bit
80386 275,000 32 bit
80486 1,600,000 32 bit
Pentium 3,300,000 64 bit external/
32 bit internal
Pentium Pro 5,500,000 64 bit
Pentium w/ MMX 4,500,000 64 bit external/
32 bit internal
Pentium II 7,500,000 64 bit
The processor has come a long way and now some of the latest processors are: Celeron • Pentium Dual-Core • Core 2 • Core i5 • Core i7 • Xeon • Itanium and who know what will come out next?
Input
One of the best features of a computer is the ability to give the computer commands and feed it information. Without an input device this would not be possible. Input devices can be built into the computer, like the keyboard in a laptop, or it can be connected to the computer by a cable. The most common input device is the keyboard. There are lots of others such as: mice, trackballs, touch pads, touch screens, pens, joy sticks, scanners, bar code readers, video and digital cameras, and microphones. In addition, storage devices such as disk drives can serve as input devices.
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Output
Input is important but equally important is the ability to read what the computer is doing. The computer output devices are used to serve the user. The most common output device is the monitor, or screen. However most computer come with speakers and a printer which are excellent output devices. Storage devices such as disk drives and diskettes also serve as output devices when it is necessary to write new or updated data files to disk or tape.
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This site was created by Roderick Hames
for the primary purpose of teaching and demonstrating computer & business skills..
Any distribution or copying without the express or written consent of
Alton C. Crews Middle School or its creator is strictly prohibited.
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Any questions, comments or suggestions concerning
this page or this Web site should be forwarded to
Roderick Hames, Computer Science / Business Education Teacher
Copyright

2010, Alton C. Crews Middle School: CS Dept - Articles

http://www.crews.org/curriculum/ex/compsci/articles/howcomput.htm