Magazine article The CPA Journal

Microcomputers 101: Understanding the Basics

Magazine article The CPA Journal

Microcomputers 101: Understanding the Basics

Article excerpt

Microcomputers are small, inexpensive, yet powerful computers that have proliferated since their introduction in the late 1970s. Current microcomputers are powerful enough to handle all but the largest business applications. Also known as personal computers (PCs) or desktop computers, most microcomputers used today fall into two classes: IBM and compatible computers, and Apple Macintosh computers.

Most business computers are IBM PCs or compatibles. These machines and their peripherals and software adhere to a set of standards originally developed by IBM. These standards are well-documented and well-understood. There are thousands of vendors and tens of thousands of software packages available for PC-compatible machines.

Using PC-compatible computers guarantees a business easy access to new hardware and software products as they are developed. A business need not be locked into a single brand or vendor and can always expand or replace computers and accessories as needed. Since PC compatibles have become so standardized, differences among competing brands can be subtle. Nevertheless, there are variations in computing speed, expandability, reliability, ease of repalr, and occasionally compatibility.


PCs are measured in terms of computing speed, internal memory, and disk capacity. Computing speed is measured in megahertz (MHz), or millions of cycles per second. This is the pulse rate of the computer, and relates to how fast it can perform calculations. The first IBM PCs operated at 4.77 MHz. Today most PCs operate between 10 and 33 MHz.

There are several classes of PC-compatible microcomputers, denoted by the type of microprocessor chip (or CPU) on which the system is based. Manufactured primarily by Intel Corp., this chip is the "brain" of the computer. The chips currently used in most microcomputers, in order of increasing cost and sophistication, are the 8088, 80286, 80386SX, 80386, and 80486.

The original IBM PCs introduced in 1981 used 8088 chips. IBM's AT, a more advanced computer introduced in 1984, used an 80286. Systems based on the 8088 are generally underpowered for current applications. Even 80286 machines can be underpowered and sometimes incompatible with more sophisticated applications. 80386SX machines are usually well-suited for use as business workstations, while 80386 and 80486 based systems are best suited to tasks requiring unusually large computing power.


Computers use memory known as RAM (random access memory) to hold programs and data. This memory is erased when you switch from one task to another or turn the computer off. RAM is not suited for long term storage.

Memory is measured in megabytes (MB), each slightly more than a million characters. Most modern PCs have one or two MB of RAM, which is enough for most applications. This RAM can always be expanded to four or more megabytes.

Disk storage is used for long-term storage of programs and data. Disks retain their data for years, even after the power is removed. They are slower than RAM--access times are measured in thousandths instead of millionths of a second. However, their low cost per megabyte and high reliability make them appropriate for mass storage of data.

Almost all PCs have a flexible or "floppy" diskette drive that uses small, square plastic diskettes to store data. These come in two sizes, 5-1/4" and 3-1/2" (the 3-1/2" disk stores more data, typically about one million characters). A hard disk drive is a faster, larger storage device. While the diskettes that go into a floppy drive can be taken in and out, the hard drive generally has no removable parts. …

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