THE DIFFERENT STYLES OF PERSONAL COMPUTERS

The world of personal computers is one of Apples, Lisa’s, Macintosh's, Compaq’s, Commodores, Eagles, Data Generals, and half a hundred others. While they all function much the same, not all are suitable for the needs of business, industry, or government. For example, many computers found in homes may be fine for video games or for handling a basic budget, but they often lack the capabilities and memory needed to handle most business applications. In business and industry, the IBM Personal Computer (IBM PC) has emerged as the primary machine for desktop computing. The IBM PC, also known as the Model One, is that company’s first entry into the personal computer market. The Model One, shown in Figure 23 with a monochrome monitor, has two disk drives, which means that it offers no internal long-term storage and is dependent on diskettes for its instructions and for storing work. The disk drives are the two open slots on the front of the microprocessor as pictured in Figure 23. The diskette containing the software program is placed in the left-hand drive and the diskette on which the work will be stored is put in the drive on the right. The system identifies the disk drives as:

FIGURE 23. Dual disk drive system. Courtesy of International Business Machines.

Drive A (the disk drive on the left)

Drive B (the disk drive on the right)

When the machine is turned off, it loses everything that was stored on it

The IBM XT, pictured in Figure 24 with a color monitor, has a hard disk installed, which makes internal long—term storage possible. This machine has one disk drive unit and a hard fixed disk. Diskettes containing the software or data to be worked on are loaded through the disk drive and then copied to the hard disk, which generally has a storage capacity of 10 megabytes.

The system identifies each of these units as:

Drive A (the disk drive on the left)

Drive C (the hard fixed disk)

A fixed disk drive makes it easier to switch from one program to another. It is also easier to integrate information from various

 

FIGURE 24. IBM hard disk system. Courtesy of International Business Machines.

Programs and files into a single document. An example would be to merge sections from an electronic spreadsheet program into a report being prepared under a word processing program. Un- like the PC, the XT will retain anything stored on its hard disk whenever the power is turned off. While each system can be equipped with up to 640K of short- term memory (RAM), there are some differences in the mother boards, which contain the main circuitry for a personal computer. The XT has the ability to add or expand the system by five additional devices or functions over what the PC can handle. Hard disks also operate faster than diskette drives. This allows access to more information at greater speeds. Another version of the PC is the AT, which can process information two or three times faster than an XT and has a fixed disk storage capacity of 20 megabytes. Figure 25 is a 3270 personal computer. Essentially, this is an XT that has been modified to also act as if it were a terminal connected to a mainframe. While this capability can exist in any personal computer in which an emulation board has been installed, a 3270 has everything built right in.

FIGURE 25. IBM 3270 Personal Computer. Courtesy of International Business Machines.

The 3270 personal computer also has a feature called windowing, which allows the display screen to be divided into as many as seven separate work areas. An analogy would be putting a report together from different piles of information. Instead of stacking everything on a desk, the computer can display data from up to four different sources simultaneously. There are also windows on which notes or reminders can be written and displayed. Portable computers such as the Compaq and Data General/One Laptop (see Figure 26) are also popular. These machines are often equipped the same way a desktop system is, and can perform identical functions and run the same software programs. Portable computers are totally self-contained and come with built- in monitors, disk drives, and, on some models, fixed disks (see Figure 27).

 

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