What is Compatible Time-Sharing System.

Compatible Time-Sharing System:-

• The Compatible Time-Sharing System (CTSS), was one of the first time-sharing operating systems; it was developed at the MIT Computation Center. CTSS was first demonstrated on MIT's IBM 709 in November 1961; service to MIT users began in the summer of 1963 and was operated until 1973^[1]. During part of this time, MIT's influential Project MAC also ran a CTSS service, but the system did not spread beyond these two sites.
• Time-sharing means the system can allocate resources for two tasks or processes at once. This was a major advance, since earlier mainframes and computer systems only worked on one process at a time, in a linear fashion. Time-sharing and multi-process and multi-thread systems paved the way for the highly advanced operating systems of the last three decades.
• The original Compatible Time-Sharing System was backward-compatible with the Fortran Monitor System. It worked on an IBM 7094 mainframe computer with two 32K banks of core memory. The second bank was used for timesharing implementation. CTSS was connected to printers, punch card readers and tape drives.
• Using multiprogramming to handle multiple interactive jobs
• Processor�s time is shared among multiple users
• Multiple users simultaneously access the system through terminals
• CTSS had one of the first computerized text formatting utilities, called RUNOFF (the successor of DITTO).
• CTSS had one of the first inter-user messaging implementations, possibly inventing email.
• MIT Computation Center staff member Louis Pouzin created for CTSS a command called RUNCOM, which executed a list of commands contained in a file. (He later created a design for the Multics shell that was implemented by Glenda Schroeder which in turn inspired Unix shell scripts.) RUNCOM also allowed parameter substitution.
• CTSS had the text editor QED, the predecessor of ed, vi, and vim, with regular expressions added by Ken Thompson.
• CTSS was the first computer system to implement password login.
• CTSS used a modified IBM 7090 mainframe computer that had two 32,768 (32K) 36-bit-word banks of core memory instead of the normal one. One bank was reserved for the time-sharing supervisory program, the other for user programs. CTSS had a protected-mode kernel, the supervisor's functions in the A-core (memory bank A) could be called only by software interrupts, like in the modern operating systems. Causing memory-protection interrupts were used for software interrupts. Processor allocation scheduling with a quantum time unit 200 ms, was controlled by a multilevel feedback queue. It also had some special memory-management hardware, a clock interrupt and the ability to trap certain instructions