TSS/8 is a discontinued

time-sharing In computing, time-sharing is the sharing of a computing resource among many users at the same time by means of multiprogramming and multi-tasking.DEC Timesharing (1965), by Peter Clark, The DEC Professional, Volume 1, Number 1 Its emergence ...

operating system An operating system (OS) is system software that manages computer hardware, software resources, and provides common daemon (computing), services for computer programs. Time-sharing operating systems scheduler (computing), schedule tasks for ef ...

co-written by Don Witcraft and John Everett 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 unti ...

in 1967. DEC also referred to it as Timeshared-8 and EduSystem 50. The operating system runs on the

12-bit Possibly the best-known 12-bit CPU is the PDP-8 and its relatives, such as the Intersil 6100 microprocessor produced in various forms from August 1963 to mid-1990. Many analog to digital converters (ADCs) have a 12-bit resolution. Some PIC mic ...

PDP-8 The PDP-8 is a 12-bit minicomputer that was produced by Digital Equipment Corporation (DEC). It was the first commercially successful minicomputer, with over 50,000 units being sold over the model's lifetime. Its basic design follows the pioneeri ...

computer and was released in 1968.

Authorship

TSS/8 was designed at

Carnegie Mellon University Carnegie Mellon University (CMU) is a private research university in Pittsburgh, Pennsylvania. One of its predecessors was established in 1900 by Andrew Carnegie as the Carnegie Technical Schools; it became the Carnegie Institute of Technology ...

with graduate student Adrian van de Goor, in reaction to the cost, performance, reliability, and complexity of IBM's

TSS/360 The IBM Time Sharing System TSS/360 is a discontinued early time-sharing operating system designed exclusively for a special model of the System/360 line of mainframes, the Model 67. Made available on a trial basis to a limited set of custome ...

(for their Model 67). Don Witcraft wrote the TSS/8 scheduler, command decoder and UUO (''Unimplemented User Operations'') handler. John Everett wrote the disk handler, file system, TTY (

teletypewriter A teleprinter (teletypewriter, teletype or TTY) is an electromechanical device that can be used to send and receive typed messages through various communications channels, in both point-to-point and point-to-multipoint configurations. Initia ...

) handler and 680-I service routine for TSS/8. Roger Pyle and John Everett wrote the

Disk Monitor System, and John Everett adapted PAL-III to make PAL-D for DMS. Bob Bowering, author of MACRO for the

PDP-6 The PDP-6, short for Programmed Data Processor model 6, is a computer developed by Digital Equipment Corporation (DEC) during 1963 and first delivered in the summer of 1964. It was an expansion of DEC's existing 18-bit systems to use a 36-bit ...

and

PDP-10 Digital Equipment Corporation (DEC)'s PDP-10, later marketed as the DECsystem-10, is a mainframe computer family manufactured beginning in 1966 and discontinued in 1983. 1970s models and beyond were marketed under the DECsystem-10 name, especi ...

, wrote an expanded version, PAL-X, for TSS/8.

Architecture

This timesharing system is based on a protection architecture proposed by Adrian Van Der Goor, a grad student of

Gordon Bell Chester Gordon Bell (born August 19, 1934) is an American electrical engineer and manager. An early employee of Digital Equipment Corporation (DEC) 1960–1966, Bell designed several of their PDP machines and later became Vice President of Engi ...

's at

Carnegie-Mellon Carnegie Mellon University (CMU) is a private research university in Pittsburgh, Pennsylvania. One of its predecessors was established in 1900 by Andrew Carnegie as the Carnegie Technical Schools; it became the Carnegie Institute of Technology ...

. It requires a minimum of 12K words of memory and a swapping device; on a 24K word machine, it can give good support for 17 users. Each user gets a virtual 4K PDP-8; many of the utilities users run on these virtual machines are modified versions of utilities from the Disk Monitor System or paper-tape environments. Internally, TSS/8 consists of RMON, the

resident monitor In computing, a resident monitor is a type of system software program that was used in many early computers from the 1950s to 1970s. It can be considered a precursor to the operating system. The name is derived from a program which is always pre ...

, DMON, the disk monitor (file system), and KMON, the keyboard monitor (command shell). BASIC is well supported, while restricted (4K) versions of FORTRAN D and Algol are available. Like IBM's CALL/OS, it implements language variants: * FORTRAN-D can only access 2 data files at a time, and the entire program is MAIN: no subroutines. * BASIC-8 programs are limited to 350 lines, but "chaining" allows "programs of virtually any length." BASIC-8 is based on

Dartmouth BASIC Dartmouth BASIC is the original version of the BASIC programming language. It was designed by two professors at Dartmouth College, John G. Kemeny and Thomas E. Kurtz. With the underlying Dartmouth Time Sharing System (DTSS), it offered an inte ...

but lacks matrix operations, implicit declaration of small arrays, strings, ON-GOTO/GOSUB, TAB, and multiline DEF FN statements. * PAL-D (Program Assembly Language/Disk) allows the "full standard" but, like all TSS/8 programs, is restricted to 4K. * ALGOL is implemented as a known standard subset, "IFIP Subset ALGOL 60." It also supports DEC's FOCAL, which was developed specifically for the PDP 8/E and it provides an algebraic language as well as a desk calculator mode.

Historical notes

* TSS/8 sold more than 100 copies. * Operating costs were about 1/20 of TSS/360. TSS/8 is also designed to be more cost-effective than the PDP-10 "for jobs with low computational requirements (like editing)". * The RSTS-11

is a descendant of TSS/8.

References

{{Time-sharing operating systems DEC operating systems Time-sharing operating systems 1968 software