The PCjr’s code name was “peanut”, and it was referred to as such by several trade magazines both before and slightly after the PCjr’s debut.
The popular 1980s adventure game series King’s Quest was originally developed for the PCjr, as IBM had commissioned Sierra On-Line for a game that would take advantage of the PCjr’s expanded graphics and sound capabilities for the product’s launch.
The cartridge BASIC for the PCjr gave the advantage of a real programming language always ready without taking up system memory, as it was firmware, with its own address space. It would interpret on the fly with speeds close to what could be achieved with use of the IBM BASIC compiler, partially due to the fact that code hosted in ROM executed faster than code stored in RAM. This made the PCjr an ideal development platform for BASIC programmers doing ad hoc data processing.
The two front cartridge slots were also used with third-party cartridges to update the system BIOS and other firmware. Multiple patches from various vendors were included on a single “combo-cartridge” used to support add-on hardware, bypass certain limitations of design, and keep up with changing OS requirements.
The PCjr was manufactured in Lewisburg, TN by Teledyne. Roughly 500,000 units were shipped.
The internal name used for the first prototype was “Green Dragon”.
Several upgrades for the PCjr were designed by IBM/Teledyne but never reached the store shelves before the IBM PCjr was canceled. These included a wireless joystick and various memory/drive upgrades.
Other than the Tandy 1000 and Amstrad IBM PC compatible lines a few years later, the dual built-in joystick ports introduced by the PCjr never became standard on IBM PC compatibles, and haven’t been seen since.
Most programs prepared for the cartridge format were entertainment titles, but a limited amount of business software was also available on cartridge, including a PCjr version of Lotus 1-2-3 and Andrew Tobias’ Managing Your Money.
The lightpen port was later used in combination with the serial port to attach an optic mouse.
The PCjr could be purchased with full manuals that included BIOS source code and all hardware schematics. This made hobby/home modifications easier and led to a number of small hardware upgrade companies providing hardware expansions and modifications (usually for compatibility). Most of these companies were eventually absorbed by PC Enterprises.