machine-specific as they used direct hardware access for speed, bypassing the OS and BIOS (this was also a common problem in early DOS machines). Bill Gates claimed that the Apple II series with a Z-80 SoftCard was the single most-popular CP/M hardware platform. Many different brands of machines ran the operating system, some notable examples being the Altair 8800, the IMSAI 8080, the Osborne 1 and Kaypro luggables, and MSX computers. The best-selling CP/M-capable system of all time was probably the Amstrad PCW. In the UK, CP/M was also available on Research Machines educational computers (with the CP/M source code published as an educational resource), and for the BBC Micro when equipped with a Z80 co-processor. Furthermore, it was available for the Amstrad CPC series, the Commodore 128, TRS-80, and later models of the ZX Spectrum. CP/M 3 was also used on the NIAT, a custom handheld computer designed for A.C. Nielsen's internal use with 1 MB of SSD memory. Multi-user In 1979, a multi-user compatible derivative of CP/M was released. MP/M allowed multiple users to connect to a single computer, using multiple terminals to provide each user with a screen and keyboard. Later versions ran on 16-bit processors. CP/M Plus The last 8-bit version of CP/M was version 3, often called CP/M Plus, released in 1983. Its BDOS was designed by Brown. It incorporated the bank switching memory management of MP/M in a single-user single-task operating system compatible with CP/M 2.2 applications. CP/M 3 could therefore use more than 64 KB of memory on an 8080 or Z80 processor. The system could be configured to support date stamping of files. The operating system distribution software also included a relocating assembler and linker. CP/M 3 was available for the last generation of 8-bit computers, notably the Amstrad PCW, the Amstrad CPC, the ZX Spectrum +3, the Commodore 128, MSX machines and the Radio Shack TRS-80 Model 4. 16-bit versions There were versions of CP/M for some 16-bit CPUs as well. The first version in the 16-bit family was CP/M-86 for the Intel 8086 in November 1981. Kathryn Strutynski was the project manager for the evolving CP/M-86 line of operating systems. At this point, the original 8-bit CP/M became known by the retronym CP/M-80 to avoid confusion. CP/M-86 was expected to be the standard operating system of the new IBM PCs, but DRI and IBM were unable to negotiate development and