Idris is a multi-tasking, Unix-like

Unix-like

A Unix-like operating system is one that behaves in a manner similar to a Unix system, while not necessarily conforming to or being certified to any version of the Single UNIX Specification....

, multi-user, real-time operating system

Real-time operating system

A real-time operating system is an operating system intended to serve real-time application requests.A key characteristic of a RTOS is the level of its consistency concerning the amount of time it takes to accept and complete an application's task; the variability is jitter...

 released by Whitesmiths

Whitesmiths

Whitesmiths Ltd. was a software company based in Westford, Massachusetts. It sold a Unix-like operating system called Idris, as well as the first commercial C compiler...

, of Westford, Massachusetts

Westford, Massachusetts

Westford is a town in Middlesex County, Massachusetts, United States. The population was 21,951 at the 2010 census.-History:Originally a part of neighboring Chelmsford, West Chelmsford soon grew large enough to sustain its own governance, and was officially incorporated as Westford on September 23,...

. The product was commercially available from 1979 through 1988.

Background

Idris was originally written for the PDP-11

PDP-11

The PDP-11 was a series of 16-bit minicomputers sold by Digital Equipment Corporation from 1970 into the 1990s, one of a succession of products in the PDP series. The PDP-11 replaced the PDP-8 in many real-time applications, although both product lines lived in parallel for more than 10 years...

 by P. J. Plauger

P. J. Plauger

P. J. Plauger is an author and entrepreneur.He has written and co-written articles and books about programming style, software tools, and the C programming language....

, who started working on Idris in August 1978. It was binary compatible with Unix V6

Version 6 Unix

Sixth Edition Unix, also called Version 6 Unix or just V6, was the first version of the Unix operating system to see wide release outside Bell Labs. It was released in May 1975 and, like its direct predecessor, targeted the DEC PDP-11 family of minicomputers...

 on PDP-11, but it could run on non-memory managed systems (like LSI-11 or PDP-11/23) as well. The kernel required 31 Kb of RAM, and the C compiler (provided along with the standard V6 toolset) had more or less the same size.

Ports

Although Idris was initially available for the PDP-11, it later ported to run on a number of platforms, such as the VAX

VAX

VAX was an instruction set architecture developed by Digital Equipment Corporation in the mid-1970s. A 32-bit complex instruction set computer ISA, it was designed to extend or replace DEC's various Programmed Data Processor ISAs...

, Motorola 68000

Motorola 68000

The Motorola 68000 is a 16/32-bit CISC microprocessor core designed and marketed by Freescale Semiconductor...

, System/370

System/370

The IBM System/370 was a model range of IBM mainframes announced on June 30, 1970 as the successors to the System/360 family. The series maintained backward compatibility with the S/360, allowing an easy migration path for customers; this, plus improved performance, were the dominant themes of the...

 and Intel 8086

Intel 8086

The 8086 is a 16-bit microprocessor chip designed by Intel between early 1976 and mid-1978, when it was released. The 8086 gave rise to the x86 architecture of Intel's future processors...

. In 1986, David M. Stanhope and Skip Tavakkolian at Computer Tools International ported Idris to the Atari ST

Atari ST

The Atari ST is a home/personal computer that was released by Atari Corporation in 1985 and commercially available from that summer into the early 1990s. The "ST" officially stands for "Sixteen/Thirty-two", which referred to the Motorola 68000's 16-bit external bus and 32-bit internals...

 and developed its ROM

Read-only memory

Read-only memory is a class of storage medium used in computers and other electronic devices. Data stored in ROM cannot be modified, or can be modified only slowly or with difficulty, so it is mainly used to distribute firmware .In its strictest sense, ROM refers only...

 boot cartridge. This work also included a port of X

X Window System

The X window system is a computer software system and network protocol that provides a basis for graphical user interfaces and rich input device capability for networked computers...

 to Idris. Computer Tools and Whitesmiths offered it to Atari

Atari

Atari is a corporate and brand name owned by several entities since its inception in 1972. It is currently owned by Atari Interactive, a wholly owned subsidiary of the French publisher Atari, SA . The original Atari, Inc. was founded in 1972 by Nolan Bushnell and Ted Dabney. It was a pioneer in...

 as a replacement for Atari TOS

Atari TOS

TOS is the operating system of the Atari ST range of computers. This range includes the 520 and 1040ST, their STF/M/FM and STE variants and the Mega ST/STE. Later, 32-bit machines were developed using a new version of TOS, called MultiTOS, which allowed multitasking...

, but eventually marketed it directly to ST enthusiasts.

A specific version of Idris (CoIdris) was packaged as a .com file

COM file

In many computer operating systems, a COM file is a type of executable file; the name is derived from the file name extension .COM. Originally, the term stood for "Command file", a text file containing commands to be issued to the operating system , on many of the Digital Equipment Corporation mini...

 under MS-DOS

MS-DOS

MS-DOS is an operating system for x86-based personal computers. It was the most commonly used member of the DOS family of operating systems, and was the main operating system for IBM PC compatible personal computers during the 1980s to the mid 1990s, until it was gradually superseded by operating...

 and used it for low level I/O

I/O

I/O may refer to:* Input/output, a system of communication for information processing systems* Input-output model, an economic model of flow prediction between sectors...

 services. Idris was ported to the Apple Macintosh (as MacIdris) by John O'Brien (of Whitesmiths Australia) and remained available until the early 1990s.

MacIdris ran as an application under the Finder

Finder

Finder may refer to:* Finder , a core component of the Apple Macintosh operating system, is the graphical representation of the computer's file system* Finder , a comic book series by Carla Speed McNeil...

 or Multifinder

MultiFinder

MultiFinder was the name of an extension software for the Apple Macintosh, introduced on August 11, 1987 and included with System Software 5. It added the ability to co-operatively multitask between several applications at once – a great improvement over the previous systems, which could only...

After Whitesmiths had been merged with Intermetrics

Intermetrics

Intermetrics, Inc. was a software company founded in Cambridge, Massachusetts in 1969 by several veterans of M.I.T.'s Instrumentation Laboratory who had worked on the software for NASA's Apollo Program including the Apollo Guidance Computer....

, Idris — along with its development toolchain

Toolchain

In software, a toolchain is the set of programming tools that are used to create a product...

 — was ported to the INMOS T800 transputer architecture.