MICA was the codename of the operating system developed for the
DEC PRISM
PRISM (Parallel Reduced Instruction Set Machine) was a 32-bit RISC instruction set architecture (ISA) developed by Digital Equipment Corporation (DEC). It was the outcome of a number of DEC research projects from the 1982–1985 time-frame, and t ...
architecture. MICA was designed by a team at
Digital Equipment Corporation
Digital Equipment Corporation (DEC ), using the trademark Digital, was a major American company in the computer industry from the 1960s to the 1990s. The company was co-founded by Ken Olsen and Harlan Anderson in 1957. Olsen was president unt ...
led by
Dave Cutler
David Neil Cutler Sr. (born March 13, 1942) is an American software engineer. He developed several computer operating systems, namely Microsoft's Windows NT, and Digital Equipment Corporation's RSX-11M, VAXELN, and VMS.
Personal history
Cutl ...
.
MICA's design was driven by Digital's need to provide a migration path to PRISM for Digital's
VAX/VMS
OpenVMS, often referred to as just VMS, is a multi-user, multiprocessing and virtual memory-based operating system. It is designed to support time-sharing, batch processing, transaction processing and workstation applications. Customers using Ope ...
customers, as well as allowing PRISM systems to compete in the increasingly important Unix market. MICA attempted to address these requirements by implementing VMS and
ULTRIX
Ultrix (officially all-caps ULTRIX) is the brand name of Digital Equipment Corporation's (DEC) discontinued native Unix operating systems for the PDP-11, VAX, MicroVAX and DECstations.
History
The initial development of Unix occurred on DEC equip ...
''user interfaces'' on top of a common kernel that could support the
system calls
In computing, a system call (commonly abbreviated to syscall) is the programmatic way in which a computer program requests a service from the operating system on which it is executed. This may include hardware-related services (for example, acc ...
(or "system services" in VMS parlance), libraries and utilities needed for both environments.
MICA was cancelled in 1988 along with the PRISM architecture, before either project was complete. MICA is most notable for inspiring the design of
Windows NT
Windows NT is a proprietary graphical operating system
An operating system (OS) is system software that manages computer hardware, software resources, and provides common services for computer programs.
Time-sharing operating systems sc ...
.
When the PRISM architecture evolved into the
DEC Alpha
Alpha (original name Alpha AXP) is a 64-bit reduced instruction set computer (RISC) instruction set architecture (ISA) developed by Digital Equipment Corporation (DEC). Alpha was designed to replace 32-bit VAX complex instruction set computers ...
architecture, Digital opted to port
OSF/1
OSF/1 is a variant of the Unix operating system developed by the Open Software Foundation during the late 1980s and early 1990s. OSF/1 is one of the first operating systems to have used the Mach kernel developed at Carnegie Mellon University, and ...
and VMS to Alpha instead of reusing MICA.
Design goals
The original goal for MICA was that all applications would have full and interchangeable access to both the VMS and ULTRIX interfaces, and that a user could choose to log in to an ULTRIX or VMS environment, and run any MICA application from either environment.
However, it proved to be impossible to provide both full ULTRIX and full VMS compatibility to the same application at the same time, and Digital scrapped this plan in favour of having a separate Unix operating system based on
OSF/1
OSF/1 is a variant of the Unix operating system developed by the Open Software Foundation during the late 1980s and early 1990s. OSF/1 is one of the first operating systems to have used the Mach kernel developed at Carnegie Mellon University, and ...
(this was variously referred to as ''PRISM ULTRIX'' or ''OZIX''). As a result, MICA would have served as a portable implementation of a VMS-like operating system, with compatible implementations of
DCL,
RMS,
Files-11
Files-11 is the file system used by Digital Equipment Corporation OpenVMS operating system, and also (in a simpler form) by the older RSX-11. It is a hierarchical file system, with support for access control lists, record-oriented I/O, remote ...
,
VAXclusters, and the VAX/VMS RTLs and system services. Proposals were made for reinstating Unix compatibility in MICA on a per-application basis so that a MICA application could be compiled and linked against the VMS interfaces, or the ULTRIX interfaces, but not both simultaneously.
Due to scheduling concerns, the first PRISM systems would have been delivered with restricted subsets of the full MICA operating system. This included systems such as ''Cheyenne'' and ''Glacier'' which were dedicated to running specific applications, and where direct interaction with the operating system by customers would be limited.
Programming
MICA was to be written almost entirely in a
high-level programming language
In computer science, a high-level programming language is a programming language with strong Abstraction (computer science), abstraction from the details of the computer. In contrast to low-level programming languages, it may use natural language ...
named ''PILLAR''. PILLAR evolved from ''EPascal'' (the
VAXELN
VAXELN (typically pronounced "VAX-elan") is a discontinued real-time operating system for the VAX family of computers produced by the Digital Equipment Corporation (DEC) of Maynard, Massachusetts.
As with RSX-11 and VMS, Dave Cutler was the ...
-specific dialect of
Pascal
Pascal, Pascal's or PASCAL may refer to:
People and fictional characters
* Pascal (given name), including a list of people with the name
* Pascal (surname), including a list of people and fictional characters with the name
** Blaise Pascal, Fren ...
) via an interim language called the ''Systems Implementation Language'' (SIL).
PILLAR would have been backported to VAX/VMS, allowing applications to be developed that could be compiled for both VAX/VMS and MICA. A common set of high-level runtime libraries named ''ARUS'' (Application Runtime Utility Services) would have further facilitated portability between MICA, OSF/1, VAX/VMS and ULTRIX. As part of the PRISM project, a common optimizing
compiler backend
In computing, a compiler is a computer program that translates computer code written in one programming language (the ''source'' language) into another language (the ''target'' language). The name "compiler" is primarily used for programs that ...
named ''GEM'' was developed (this survived and became the compiler backend for the Alpha and Itanium ports of VMS, as well as
Tru64
Tru64 UNIX is a discontinued 64-bit UNIX operating system for the Alpha instruction set architecture (ISA), currently owned by Hewlett-Packard (HP). Previously, Tru64 UNIX was a product of Compaq, and before that, Digital Equipment Corporation (DE ...
).
In addition to PILLAR, Mica provided first-class support for
ANSI C
ANSI C, ISO C, and Standard C are successive standards for the C programming language published by the American National Standards Institute (ANSI) and ISO/IEC JTC 1/SC 22/WG 14 of the International Organization for Standardization (ISO) and the ...
in order to support Unix applications.
An
assembler
Assembler may refer to:
Arts and media
* Nobukazu Takemura, avant-garde electronic musician, stage name Assembler
* Assemblers, a fictional race in the ''Star Wars'' universe
* Assemblers, an alternative name of the superhero group Champions of A ...
named ''SPASM'' (Simplified PRISM Assembler) was intended for the small amount of assembly code needed for the operating system, and would not have been made generally available in order to dissuade customers from developing non-portable software. Similarly, an implementation of
BLISS
BLISS is a system programming language developed at Carnegie Mellon University (CMU) by W. A. Wulf, D. B. Russell, and A. N. Habermann around 1970. It was perhaps the best known system language until C debuted a few years later. Since then, C b ...
was developed for internal use only, in order to allow pre-existing VAX/VMS applications to be ported to MICA. MICA would have featured ports or rewrites of many VAX/VMS layered products, including
Rdb,
VAXset, DECwindows, and most of the compilers available for VAX/VMS.
Legacy
When PRISM and MICA were cancelled, Dave Cutler left Digital for
Microsoft
Microsoft Corporation is an American multinational technology corporation producing computer software, consumer electronics, personal computers, and related services headquartered at the Microsoft Redmond campus located in Redmond, Washing ...
, where he was put in charge of the development of what became known as
Windows NT
Windows NT is a proprietary graphical operating system
An operating system (OS) is system software that manages computer hardware, software resources, and provides common services for computer programs.
Time-sharing operating systems sc ...
. Cutler's architecture for NT was heavily inspired by many aspects of MICA.
In addition to the implementation of multiple operating system APIs on top of a common kernel (
Win32
The Windows API, informally WinAPI, is Microsoft's core set of application programming interfaces (APIs) available in the Microsoft Windows operating systems. The name Windows API collectively refers to several different platform implementations th ...
,
OS/2
OS/2 (Operating System/2) is a series of computer operating systems, initially created by Microsoft and IBM under the leadership of IBM software designer Ed Iacobucci. As a result of a feud between the two companies over how to position OS/2 ...
and
POSIX
The Portable Operating System Interface (POSIX) is a family of standards specified by the IEEE Computer Society for maintaining compatibility between operating systems. POSIX defines both the system- and user-level application programming interf ...
in NT's case) MICA and NT shared
the separation of the kernel from the executive,
the use of an
Object Manager
Object Manager (internally called Ob) is a subsystem implemented as part of the Windows Executive which manages Windows ''resources''. Resources, which are surfaced as logical ''objects'', each reside in a namespace for categorization. Resources ...
as the abstraction for interfacing with operating system data structures, and support for
multithreading and
symmetric multiprocessing
Symmetric multiprocessing or shared-memory multiprocessing (SMP) involves a multiprocessor computer hardware and software architecture where two or more identical processors are connected to a single, shared main memory, have full access to all ...
.
After the cancellation of PRISM, Digital began a project to produce a faster VAX implementation which could run VMS and provide comparable performance to its
DECstation
The DECstation was a brand of computers used by DEC, and refers to three distinct lines of computer systems—the first released in 1978 as a word processing system, and the latter (more widely known) two both released in 1989. These compri ...
line of Unix systems.
When these attempts failed, the design group concluded that VMS itself could be ported to a PRISM-like architecture. This led to the
DEC Alpha
Alpha (original name Alpha AXP) is a 64-bit reduced instruction set computer (RISC) instruction set architecture (ISA) developed by Digital Equipment Corporation (DEC). Alpha was designed to replace 32-bit VAX complex instruction set computers ...
architecture, and the
Alpha port of VMS.
References
{{Operating System
Digital Equipment Corporation
DEC operating systems
Proprietary operating systems
Time-sharing operating systems