Olivetti M20
The Olivetti M20 is a Zilog Z8000 based computer designed and released by Olivetti in 1982. Although it offered good performance, it suffered from a lack of software due to its use of the Z8000 processor and custom operating system, PCOS. The company introduced the IBM PC compatible Olivetti M24 in 1983 and the M20 line was phased out.

History
System design began in 1979 in Cupertino (California) at Olivetti's Advanced Technology Center. When announced on March 31, 1982, it was probably the first 16-bit personal computer in Europe with an expected price range of US$3,000-6,000.

InfoWorld magazine saw the M20 as an "answer to Tandy's Model 16, the IBM Personal Computer and the Apple III"; Olivetti itself compared its computer to the IBM PC, Sirius Victor, Commodore 8000 and Apple II in television advertising.

Although the computer was initially well received, its use of a non-standard OS (Olivetti's proprietary PCOS) and CPU (Zilog Z8001) proved to be its most serious limitations. The first major software package was a word processor by SofSys called Executive Secretary, followed later by another word processor, OliWord, and business software, Olibiz. There was also Microsoft BASIC 5.2 with full support for the hardware's features.

To alleviate a lack of applications, Olivetti sold a CP/M emulator for US$300 and distributed certain CP/M software packages (dBase II and SuperCalc) for their computer. Olivetti later introduced the "Alternate Processor Board" (APB 1086), based on an 8 MHz Intel 8086 CPU for compatibility with MS-DOS and CP/M-86 software.

In January 1984, Olivetti introduced a new IBM PC-compatible computer, the Olivetti M24, running MS-DOS as a "complement" to the Olivetti M20.

Olivetti sold around 50,000 M20 computers in the first year of production.

Features

M20 uses Zilog Z8001 4 MHz CPU and 128 KB RAM, which can be expanded up to 512 KB by three 128 KB memory boards. Keyboard, motherboard and disk drives are contained in all-in-one unit with separate monitor. The computer has also parallel (IEEE-488) and serial port (RS-232-C).
Standard configuration includes two 5-inch 320 KB floppy disk drives (286 KB formatted capacity). Optional were 160 KB or 640 KB (compatible with 320 KB disks) drives or 5-inch hard disk in place of one of the floppy disk drives (9.2 MB formatted capacity).

Motherboard has two expansion slots intended for the hard disk controller board, additional parallel interface, twin serial interface or Corvus Omninet LAN card. This slot is also used by the APB 1086 CPU card.

M20 provides 512 × 256 display resolution on 12-inch monochrome or color monitor. With memory expanded by two 32 KB memory boards, the computer can display 8 colors. When using only one additional memory board, only 4 colors form 8 color palette are available. All graphics is pixel-generated (there is no specific text mode), text characters use resolution 64 characters per 16 rows (or 80 characters per 25 rows).

Keyboard lacks delete, tab and backspace keys - their function can be mapped on S1 or S2 special keys by the "Change Key" system utility. Instead of standard function keys, user defined special functions are invoked by pressing orange-colored "Command" or light-blue-colored "Control" key along with another key (creates 24 user-definable function keys). Numeric keypad serves also as cursor controls.

PCOS
PCOS (Professional Computer Operating System) is a single-user, single-tasking operating system. It was used on the Olivetti M20 and L1 computers. The first version (PCOS 1.0) supports 14 characters long filenames, with no directories and a limit of 192 files per disk (called volume).   
PCOS requires significant part of the main memory. Operating system with BASIC interpreter takes 64 KB RAM, another 16 KB are reserved for screen output and user is left with only around 40 KB RAM on unexpanded machine. Version 2.0 supports dynamic memory allocation alleviating segmented memory limitations of the Z8000 CPU.
PCOS can protect by password volumes (disks), individual files and BASIC programs (against listing/editing/copying). Standard OS configuration includes BASIC interpreter, other programming languages (Assembler and PASCAL) are optional.

Example PCOS commands: 
 vformat - formats a volume
 vrename - changes the name of a volume
 vpass - changes the volume password
 vlist - file list 
 vquick - quick file list
 vcopy -  volume copy
 fcopy - file copy
 flist - display a text file contents
 basic - run the BASIC interpreter
 dconfig - system configuration
 slanguage - system regional settings

Notes

References

External links
Video, Retro Computer museum, Zatec, Czech Republic video

Olivetti personal computers
Computer-related introductions in 1982