The Olivetti Personal Computer M21 is a complete computer system, providing the full range of hardware and software options normally associated only with desktop personal computers. Based on the Intel 8086 microprocessor, the M21 supports the following operating systems: MS-DOS,  Concurrent CP/M-86 and the UCSD p-System.

With these operating system options, users can choose from a vast range of application software to meet their processing needs.
A comprehensive set of programming languages is also provided, for users who want to develop their own applications: BASIC, COBOL, Pascal, FORTRAN, C Language and Assembler.

The flexibility of the system's software is matched by its hardware. Memory capacity starts at 128K bytes and can be expanded to 640K bytes. In terms of external storage, the system offers a variety of options: 320/360K byte diskette(s), 640/720K byte diskette(s) and a 10 Mbyte hard disk unit.

The system supports an integrated 9" monochrome video, this video provides advanced graphics features with a maximum resolution of 640 x 400 pixels. If a larger screen is required, or colour output is wanted, either of the M24's 12" videos can be connected.

The keyboard is a compact, industry-standard 83-key input device. During transit, the keyboard is attached to the front of the basic module, thus protecting the video.'