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Personal computers

20 January, 2016 - 15:30

Time-sharing continued to improve resulting in a proliferation of ever smaller and cheaper “mini-computers.” They might be the size of a refrigerator rather than filling a room, but users still shared them. As hardware improved, we eventually reached the point where it was economical to give computers to individuals. The MITS Altair, introduced in 1975, was the first low-cost personal computer powerful enough to improve productivity. By the late 1970s, programmers, professional users and data entry workers were using personal computers. They were much less powerful than today’s PC, but they began to displace time-sharing systems.

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Figure 7.11 MITS Altair 
 

Programmers could write and test programs on their own machines – they could, for the first time, own their own tools and be independent of employers. They could also work at home, and hobbyist programming began to spread. Secretaries and typists began using personal computers for their work, using desktop computers with built-in programs for creating documents – the original “word processors.” Knowledge workers – managers, engineers, and others – began using personal computers to increase their productivity. Software companies quickly offered programs for word processing, maintaining small databases and doing spreadsheet calculations on personal computers.

The first personal computers used the same types of terminals as time-shared computers. They consisted of a keyboard and a printer or screen, which could display characters, but not pictures or diagrams. As such, the user interface of early personal computer operating systems was similar to that of time-sharing systems. The computer displayed a prompt indicating that it was ready for a command, which the user typed. For example, the user could erase a file called myfile.txt by typing the command:

> delete myfile.txt

As personal computer hardware improved, it became feasible to move from character displays to displays which could turn the dots making up the characters on and off individually. This made it possible to display and work with images as well as characters. Graphic displays, when coupled with a pointing device like a mouse, ushered in applications and operating systems with graphical user interfaces (GUIs). One could now delete a file by dragging icon or small picture representing it to a trashcan on the screen. The Apple Macintosh, introduced in 1984, was the first low-cost personal computer with a GUI operating system.

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Figure 7.12 The original Apple Macintosh 
 

Users liked GUIs because they did not have to memorize commands to use a program, and operating systems like the Macintosh OS and Windows have come to dominate personal computer desktops. However, character-oriented user interfaces are still popular among technicians and system administrators who operate and maintain our networks and back-end computers. They find typing commands faster than using a GUI once they have the commands memorized. It is also possible to write small programs containing several commands to automate common multi-command tasks like creating user accounts.

Personal computers with GUI operating systems like the Macintosh OS and Windows quickly made their way into homes and organizations. Their low cost encouraged the founding of many companies to develop software for the personal computer platform. Some of these, for example, Microsoft, Lotus, Adobe, and Electronic Arts, are major companies today.