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Section 8

Personal Computing Systems

In the mid-1970s, spurred by the availability of single-chip microprocessors, personal computing was born. While it is too early to make projections or draw conclusions, some general comments can nevertheless be made. By personal computing we mean a low-cost computer structure that is dedicated to a single user. The computing environment usually consists of a Pc, Mp, Mdisk, keyboard, cathode-ray tube (CRT) display with graphics and/or color, and a standard software complement. Entry-level systems (with Pc, Mp, keyboard, CRT, and ROM-based software) are frequently priced as low as $400, while systems with a full set of options may be priced up to $10,000.

Personal computers are often targeted at a particular application area, such as scientific calculation, education, business, or entertainment. As of mid-1979 over 80 companies offered one or more personal computing systems. The following three paragraphs give examples of these systems and their capabilities. Table 1 describes examples of other personal computers available during the latter part of 1978. We can expect functionality to increase and prices to decrease.


In the first 20 months they were available, Radio Shack is reported to have sold in excess of 100,000 TRS-80 systems with Pc, Mp,

Table 1 Examples of Personal Computers Using the Basic Programming Language (Late 1978) [Mennie, 1978]

Apple II

Commodore PET 2001

Exidy Sorcerer

Intelligent Systems Compucolor II

Ohio Scientific Challenger C2-8P

Radio Shack TRS-80




Zilog Z80

Intel 8080



ROM (bytes)






Level I: 4K

Level II: 12K

RAM (bytes)






Level I: 4K

Level II: 16K

Video display

Color or black- and-white TV

40 char/24 lines

Black-and-white monitor 40 char/25 lines

Black-and-white TV or monitor 64 char/30 lines

Color monitor 64 char/32 lines

Black-and-white TV or monitor 32 or 64 char/ 32 lines

Black-and-white monitor 64 char/16 lines

Keyboard style







Mass storage

Cassette tape (1,500 bit/s) Floppy disk (116 Kbyte)

Cassette tape Floppy disk

Cassette tape

Minidisk (51 Kbyte)

Cassette tape Floppy disk

Cassette tape Floppy disk (80 Kbyte)

System cost








keyboard, CRT, and ROM-resident BASIC for less than $800. The TRS-80 Model II has a Z-80 Pc (see Part 3, Sec. 2) operating at 4 MHz, 64 Kbyte of RAM, 1.5 Mbyte of floppy disk Ms, keyboard, CRT, and printer for less than $8,000. Available business software includes general ledger, accounts receivable, inventory control, mailing lists, and payroll.

TI 99/4

Based on Texas Instruments' TI 9900 (see Part 3, Secs. 1 and 2) with 16 Kbyte of RAM, the TI 99/4 features a keyboard, color CRT, extended graphics, sound and speech synthesis, the BASIC programming language, and a software library distributed in ROMs. Software is available for entertainment, education, and financial applications.


Ohio Scientific's C8PDF is aimed at the home computing market. The C8PDF can answer or place telephone calls via an acoustic coupler. It can take telephone messages by decoding Touch-Tone inputs. In the case of a problem at home, the C8PDF can dial a number and explain the situation using a built-in phonetic speech synthesizer. The computer can interface with home security systems that incorporate sensors for smoke, fire, intrusion, and AC power outages. Lights and appliances (e.g., furnace, air conditioner, and microwave oven) can also be placed under program control.

Personal computing is a subdimension of the computer function


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