Note
The 9845A came standard with a built-in mini-cartridge tape drive (217K capacity). A second tape drive was optional as was a built-in thermal printer (80 characters wide, 480 lines per minute and graphics capable). The 9845A shipped with 13K RAM standard, expandable to 62K. The computer came standard with four I/O slots and used the same interfaces as the 9825. The 9845S came standard with the additional tape drive, printer and graphics package. The 9845B replaced the 9845A in 1979. It came standard with 56K RAM, expandable to 449K. The 9845T also arrived in 1979. It came standard with 186K RAM and included the optional printer, both tape drives and the graphics package. The 9845C was introduced in 1980. It was the first computer from HP with a color screen. The 13-inch screen could display 4,913 colors. It also included both tape drives, the internal printer and a light pen. The monitor for both the 9845C and 9845T had eight programmable function keys.The 9845 was HP's number one revenue producing product in fiscal year 1980.In the previous two years since its introduction, the 9845 had also been one of the company's top five products. Introduction of the 200 Series computers in 1981 affected sales of the 9845. The 9845 was obsoleted in May of 1985.
The 9845A and 9845B are not hardware compatible. These computers share the same interfaces, monochrome monitor and internal thermal printer. However, the internal PCBs and pluggable ROM modules are different. The 9845A and 9845B are also not program compatible. The 9845A cannot run a program written on a 9845B. The 9845B also cannot run a program written on a 9845A unless it is first converted (using a utility in the 9845B utility library).