Lesson 5. Home computer

I. Read and translate the text.

II. State the problems it describes.

III. In a paragraph of 70-90 words summarize the problems involved.

The single most important item in our century’s households is the computer. These electronic brains govern everything from meal preparation and waking up the household to assembling shopping lists and keeping track of the bank balance. Sensors in kitchen appliances, climatizing units, communicators, power supply and other household utilities warn the computer when the item is likely to fail.

Computers also handle travel reservations, relay telephone messages, keep track of birthday and anniversaries, compute taxes and even figure the monthly bills for electricity, water, telephone and other utilities. Not every family has its private computer. Many families reserve time on a city or regional computer to serve their needs. The machine tallies up its own services and submits a bill, just as it does with other utilities.

A home computer was a class of personal computer entering the market in 1977 and becoming common during the 1980s. They were marketed to consumers as accessible personal computers, more capable than video game consoles. These computers typically cost much less than business, scientific or engineering-oriented desktop personal computers of the time, and were generally less powerful in terms of memory and expandability. However, a home computer often had better graphics and sound than contemporary business personal computers. Usually they were purchased for education, game play, and personal use.

Advertisements for early home computers were rife with possibilities for their use in the home, from cataloguing recipes to personal finance to home automation, but these were seldom realized in practice as they usually required the home computer user to learn computer programming.

Computers are used in the home even more today, and the line between a “business” computer and a “home” computer has blurred, since they typically use the same operating systems, processor architectures, applications and peripherals.

Background

The home computer became affordable for the general public due to the mass production of the microprocessor. Early microcomputers had front-mounted switches and blinkenlights to control and indicate internal system status, and were often sold in kit form. These kits would contain an empty printed circuit board which the purchaser would fill with the integrated circuits, other individual electronic components, wires and connectors, and then hand-solder all the connections. In contrast, home computers were designed to be used by the average consumer, not necessarily an electronics hobbyist.

Early home computers such as Sinclair ZX80, and Acorn Atom could be purchased in kit form (or assembled), other home computers were sold only pre-assembled. They were enclosed in molded plastic cases, which were attractive to consumers and lower cost than the metal card-cage enclosures used for the Altair and similar computers. A keyboard was usually built into the case. Ports for plug-in peripheral devices such as a video display, cassette tape recorders, joysticks, and (later) disk drivers either were provided or available as add-on cards.

Usually the manufacturer would provide the entire peripheral devices as extra cost accessories. Often peripherals were not interchangeable between brands of home computer (or sometimes even between successive models of the same brand).

To save the cost of a dedicated monitor, the home computer often would have connected either directly or through an RF modulator to the family TV set as video display and sound system.

Almost universally, home computers had a version of the BASIC programming language in read-only permanent memory. One exception was the Jupiter Ace, which had the Forth language built in. After the success of systems like the RadioShack TRS-80, the Commodore PET and the Apple2 in 1977, large numbers of new machines of all types began to appear during the late 1970s and early 1980s.

Home computers competed with video game consoles. The markets weren’t entirely distinct, as both could be used for games. A common marketing tactic was to show a computer system and console playing games side by side, then emphasizing the computer’s greater ability by showing it running user-created programs, educational software, word processing, spreadsheet and other applications while the game console showed a blank screen or continued playing the same repetitive game. During the peak years of the home computer market, scores of models were produced, usually with little or no thought given to compatibility between different manufacturers or even within product lines of one manufacturer. The concept of a computer platform did not exist, except for the Japanese MSX standard.

The introduction of the IBM Personal Computer in August 1981 would eventually lead to standardization in personal computers, largely due to the system’s open architecture, which encouraged production of third-party clones of the unit. While the Apple2 would be quickly displaced by the IBM PC for office use, Apple Computer’s 1984 release of the Apple Macintosh created a new model for the home computer which IBM-compatible computers would eventually imitate.

Technology

The basic layout of a typical home computer system of the era comprises the CPU/ keyboard unit, floppy disk drive, and dedicated color monitor. Many systems also had a dot matrix printer for producing paper output.

Many home computers were superficially similar. Most had a keyboard integrated into the case; sometimes a cheap-to-manufacture chiclet keyboard in the early days, although full-travel keyboards quickly became universal due to overwhelming consumer preference. Most systems could use an RF modulator to display 20-40 column text output on a home television. The use of a television set as a display almost defines the pre-PC home computer. Although computer monitors were available for this market segment, it was often a later purchase made after users had bought a floppy disk drive, printer, modem, and the other pieces of a full system. This “peripherals sold separately” is another defining characteristic of home computers. Many first time computer buyers brought a base C-64 system home to find they needed to purchase a disk drive or Datassette to be able to make use of it.

In the early 1980s, home computers were mostly based on 8-bit microprocessor technology, typically the MOS Technology 6502 or the Zilog Z80. A notable exception was the TT-99 series, announced in 1979 with a 16-bit TMS9900 CPU.

Processor clock rates were typically 1-2 MHz for 6502 based CPUs and 2-4 MHz for Z80 based systems, but this aspect of performance was not emphasized by users or manufactures, because the systems’ limited RAM capacity, graphics capabilities and storage options were of primary importance. Clock speed was considered a technical detail of interest only to users needing accurate timing. To economize on component cost, the same crystal used to produce colour television compatible signals was also used for the processor clock. This meant processors rarely operated at their full rated speed, and had the side-effect that European and North American version of the same home computer operated at slightly different speeds and different video resolution due to different television standards.

Many home computers initially used the then-ubiquitous compact audio cassettes as a storage mechanism but they were notoriously slow and unreliable. Most software for home computers remained sold on 5.25″ disks, however, 3.5″ drives were used for data storage. Standardization of disk formats was not common; sometimes even different models from the same manufacturer used different disk formats. Various copy protection schemes were developed for floppy disks but most were broken in short order, so having a backup disk of vital application software was seen as important.

In contrast to modern computers, home computers most often had their OS stored in ROM chips. This made startup times very fast — no more than a few seconds — but made upgrades difficult or impossible without buying a new unit. Usually only the most severe bugs were fixed by issuing new ROMs to replace the old ones. The user interface was usually only a BASIC interpreter coupled to a character-based screen or line editor, with applications performing all other OS duties themselves. As multitasking was not common on home computers until the 1980s, this lack of API support wasn’t of much importance. Application programs usually accessed hardware directly to perform a specific task, often “switching out” the ROM based OS to free the address space it occupied and maximize RAM capacity. Most home computers loaded their Disk Operating System (DOS) separately from the main OS. The DOS was only used to send commands to the floppy disk drive and needn’t be loaded to perform other computing functions. Many home computers also had a cartridge interface which accepted ROM-based software. This was occasionally used for expansion or upgrades such as fast loaders, and application software on cartridge did exist, but the vast majority of cartridges were games.