What are the hardware and software requirements of a time sharing system?

Answer 1

A characteristic of a time-sharing system is that the computer seen by the user programming in machine language differs from that on which the system is implemented. In fact, the user machine is defined by the combination of the time sharing hardware running in user mode and the software which controls input-output, deals with illegal actions which may be taken by a user's program, and provides various other services. If the hardware is arranged in such a way that calls on the system have the same form as the hardware instructions of the machine, then the distinction becomes irrelevant to the user; he simply programs a machine with an unusual and powerful instruction set which relieves him of many of the problems of conventional machine-language programming. In a time-sharing system that has been developed by and for the use of members of Project Genie at the University of California at Berkeley , the user machine has a number of interesting characteristics. The computer in this system is an SDS 930, a 24 bit, fixed-point machine with one index register, multi-level indirect addressing, a 14 bit address field, and 32 thousand words of 1.75 memory in two independent modules. Figure 1 shows the basic configuration of equipment. The memory is interleaved between the two modules so that processing and drum transfers may occur simultaneously. A detailed description of the various hardware modifications of the computer and their implications for the performance of the overall system has been given in a previous paper.