In a computer's world, all data storage is essentially broken down into units that exist in a state of being either on or off.  These series of off and on states are read as 1's (on) or 0's (zero's - off). Data storage is actually a series of 1's and 0's that, when put together in a certain order, are interpreted as data files, or commands and instructions. So ON is 1, and OFF is 0.

Since there are two digits that comprise this code, it is called binary code. Each 0 or 1 is called a binary digit, or "bit" for short.

Information, as humans perceive it, is usually associated with text (numbers and characters). But, for a computer to store a character, it must be stored as binary code.

Since the computer uses binary storage, each character or number requires 8 bits to store that character. This arrangement of 8 bits is called a byte; therefore:

For example, the word computer requires 8 bytes of memory, or to save/store on a disk.

This term, BYTES, is used extensively in describing physical conditions such as disk-drive capacity/ size, file size, the amount of memory (RAM), etc. Often, metric prefixes are used in addition to the term byte (kilobyte, megabyte, gigabyte) to describe disk or RAM capacity, or to describe large amounts of information.

A CD-ROM disc, at full capacity, can store about 675 MB. (675,000,000 bytes)

One book (250 pages) divided into the 450,000 pages yields a storage capacity of 1,800 books on a single 675 Meg CD-ROM disc. {How many books are there in your set of encyclopedias?}

No wonder a CD-ROM can store a whole set of encyclopedia …and a whole lot more!

And a new DVD-ROM disc holds about 4.3 GB (Digital Video Data)

Input is defined as feeding information into a computer. There are many types / methods.

Keyboard  Most common and familiar method.

Mouse  Used in the graphical (Windows) environment.

Pen Light  Combines mouse and keyboard.

Audio  Voice activated systems. Microphones, speakers, music, voice.

Joystick  Games.

Tape  Source of data or instructions. Input source for music, too.

Disks  Data / instructions source. Programs, Games, Files, Viri, etc. Your STUFF!

Scanner  Optically converts print and graphics to data, then save file, or print / fax.

Modem  Accepts and transmits data via telephone lines.

Video Video imaging. Video Cams Graphics -- Pictures

CD-ROM  DATA and MUSIC. Compact discs are "read-only."

CD-W's  Like a CD-ROM, only used in CD-W Writeable Drive to save data & "stuff". "Stuff" could be movies, songs, graphics, letters, ... just anything!

The CPU loves numbers. It only knows numbers. Processing is a particular method of doing something, generally involving a number of steps or operations.

Calculating  Adding, subtracting, multiplying and dividing.

Comparing  Can compare and select data, as instructed. "Find" / Databases.

Copying  Can move data around to create any kind of report or listing

Video (Monitor)  Screen display (Every character you type or window you see is output)

Sound (Speaker)  Error messages. Sounds, Music, Video Conferencing, Phones, etc.

RCA Jacks  Sound boards and/or headphones (music off jack on CD-ROM)

Printer  Printed output (Any dot matrix, deskjet or lazer printer)

Modem  Sending data via telephone lines. Internet ... Faxes ... Other PC's

Disks  File storage. 1.44 Floppys, IOMEGA ZIP Disks, Super Disks, etc.

Video  Video imaging, graphics Tape Storage and backup

Currently on the market, there are two main type of PC's. The two main types are the Apple / Macintosh and the IBM / IBM Compatibles (Clone).

This is the brain of the PC. It is a miniature electronic circuit containing thousands of components. These include transistors and resistors. The CPU does the thinking for the PC, controlling all the components in the system. In most PCs, it also handles number crunching or mathematics. The CPU resides on the motherboard.

The CPU works by executing instructions and telling other components, as well as itself, what to do. The CPU looks at instructions in RAM and either:

Buses are like freeways, with clock speed being much like the speed limit.

The PC uses many different buses or freeways, just as a city uses several freeways for transportation purposes. Like a city, traffic jams can occur. Similarly, buses, like freeways, come in different widths. Just as a freeway can be four, six or eight lanes, buses are described as 8-, 16-, 32-, or 64-bit.

Since it takes 8 bits to make 1 byte, and 1 byte equals one character, an 8-bit bus can carry one character at a time. A 16-bit bus can carry 2 bytes or characters; a 32-bit can carry 4 bytes/characters, and a 64-bit can carry 8 bytes or characters at a time.

The original IBM PC was based on a processor family developed by the Intel Corporation. The first members of this family were the 8086 and the 8088.

IBM selected the 8088 as the base processor for the PC. As Intel developed other, faster and more powerful members of this family, IBM and other firms adopted those processors for their PC's. A tabular display is on the next page.

The "XT" in "XT Class" machine stands for "eXperimental Technology."

As a matter of common terminology, all PC's having an 80286 processor or above are referred to as "AT Class" (Advanced Technology) machines, even though the processors beyond the '286 are much more powerful.

The hardware configurations of the early PC XT models were all done through a rather nightmarish combination of selection switches and wiring jumpers. Doing something as simple as adding more memory could turn into an all day affair.

Beginning with the AT Class machines, a new approach was beginning to take shape.

A small portion of memory was devoted to "remembering" the computer's configuration.

This little portion of memory is commonly referred to as the CMOS memory.

(CMOS, pronounced "SEE-MOSS", is an acronym for Complimentary Metal Oxide Semiconductor. It refers to the circuit's construction materials.)

It's memory is "maintained" by a very small, long life battery that allows it to keep its memory.

To understand buses and how they interact, it is important to understand what is meant by the terms "clock speed" and "MHz" (Megahertz).

One cycle is equal to 1 Hertz. (International measurement for the old Cycle Per Second)

Therefore, 1 million cycles is equal to 1 million Hz, or 1 MHz. (1 Megahertz)

For example, a school bus traveling at 16 mph is slower than a bus traveling at 33 mph.

The original IBM XT has a clock speed of 4.77 MHz, whereas an 80386 system might have a clock speed of 40 MHz.

Two years ago (Fall 98), 166 MHz was the top end processor in the market.

Today's fastest computers are now in the 900 MHz to 1.3 GHz range with 1.500 GHz on the way by the end of year 2,001. (PC Magazine)

• How much speed do you need?   It depends!   When typing a letter, how fast do you want to mis-spell words?

(The clock spoken of here has nothing to do with the real-time clock, i.e., 9:00 a.m., inside the computer. The system's clock operates like a "tuning fork" and generates a near-infinite series of pulses. The higher the occurrence (the frequency), the faster the data is transferred from one point to another point inside the computer.)

The ROM BIOS allows a program to have easy access to features in a system by calling ROM BIOS program modules instead of talking directly to the device. These are programs that must be present on the startup of the machine, for the system to operate.

The early PC/XT class of computers handled configuration via adapter cards, and/or dip switches on the motherboard. This setup was normally good forever, or until there were changes in the hardware. For all practical purposes, the PC/XT class of computer had no CMOS. That is a very different story with today's PCs.

The old systems were clumsy, difficult, and required opening the PC to change the settings. When the 80286 CPU premiered, a more flexible technique of changing these settings was utilized. The engineers designated about 1KB of memory to store the settings and a setup program for editing entries. Unlike normal RAM, the chips holding this information had to maintain the settings after the machine was 'powered down'. This was accomplished with the use of a battery and a CMOS chip that required very little power. This technology is found in the 80286 system, on up.