TSS/8

TSS/8 was designed at Carnegie Mellon University with graduate student Adrian van de Goor, in reaction to the cost, performance, reliability, and complexity of IBM's TSS/360 (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) handler and 680-I service routine for TSS/8. Roger Pyle and John Everett wrote the PDP-8 Disk Monitor System, and John Everett adapted PAL-III to make PAL-D for DMS. Bob Bowering, author of MACRO for the PDP-6 and PDP-10, 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's at Carnegie-Mellon. It requires a minimum of 12K words of memory (8K for the operating system and 4K for the user swap area) and a swapping device; The standard swapping device, called a drum, was a disk drive with a head assigned to each track so there was no delay waiting for a read/write head to be repositioned on the drive. On a 24K word machine, it can give good support for its maximum of 16 users. Like IBM's CALL/OS, it implements language variants: • PAL-D (Program Assembly Language/Disk) allows the "full standard" but, like all TSS/8 programs, is restricted to 4K. Many programs designed to work on a stand-alone machine and manipulate hardware directly would still work on TSS-8 as it emulated many I/O requests internally. • ALGOL is implemented as a known standard subset, "IFIP Subset ALGOL 60." It also supports DEC's FOCAL-8, which has been available from earlier PDP/8 models and it provides an algebraic language as well as a desk calculator mode. ==Legacy==

TSS/8 sold more than 100 copies. The RSTS-11 operating system is a descendant of TSS/8. ==References==