After launching the IBM PC (and its great success), IBM tried to stand out a standard for home computers, it created then the PC junior, which itself is a "light" version of the PC especially designed for home activities.
Despite its qualities, the PC jr had few success and never managed to replace the established home computers like Commodore 64, Apple II or Atari 800.
Two IBM PC junior models were available: a basic one and a enhanced one (supplied with 128k, 30 programs, a 5.25" floppy disk drive [360 KB] and its controller).
Contrary to the IBM PC, the power supply is not integrated to the case, but is external. The keyboard is linked by infra-red to the CPU, though there was a RJ11 (standard phone jack) plug that could be used instead to save batteries. It is impossible to connect a 8087 math co-processor.
The RS232 connector is not a standard one. To use a standard RS232 device, the user has to buy a special adapter ("Berg" style connector breakout -> D25 connector).
The PC Jr runs under MSDOS 2.1 (the same version as the PC) and handles a hard disk when it is not possible to connect hard disk on the PC Jr (go figure)!
There was an internal modem available that ran at 300 bps sold by IBM. Third party modems were also available at 1200bps.
A cartridge containing enhanced basic (with special graphics instructions) was also available. To get a 80 column text display, the extra 64k RAM expansion is needed.
Many IBM PC programs would not originally run on the PCjr because it did not include a DMA controller. This was available through a memory side-car add-on from Tecmar Systems. Many people were able to then run the PCjr as a competent business type of system as well.
Here is a section from computerhope.com: In 1822, Charles Babbage purposed and began developing the Difference Engine, considered to be the first automatic computing engine that was capable of computing several sets of numbers and making a hard copies of the results. Unfortunately, because of funding he was never able to complete a full-scale functional version of this machine. However, in June of 1991 the London Science Museum completed the Difference Engine No 2 for the bicentennial year of Babbage''s birth and later completed the printing mechanism in 2000.
And, the first electrical computer was the Z1, built by Konrad Zuse from 1936 to 1938.
Saturday 4th February 2012
My mom uses our PCjr to save cooking recipes at least up till the past few years. I don''t know how well the disks are holding up though. I''ll ask her next time I see her.