Page:CTSS programmer's guide.djvu/15



Introduction
The motivation for time-shared computer usage arises out of the slow man-computer interaction rate presently possible with the bigger, more advanced computers. This rate has changed little (and has become worse in some cases) in the last decade of widespread computer use.

In part, this effect has been due to the fact that as elementary problems become mastered on the computer, more complex problems immediately become of interest. As a result, larger and more complicated programs are written to take advantage of larger and faster computers. This process inevitably leads to more programming errors and a longer period of time required for debugging. Using current batch monitor techniques, as is done on most large computers, each program bug usually requires several hours to eliminate, if not a complete day. The only alternative hitherto available was for the programmer to attempt to debug directly at the computer, a process which is grossly wasteful of computer time and hampered seriously by the poor console communication usually available. Even if a typewriter is the console, there are usually lacking the sophisticated query and response programs which are vitally necessary to allow effective interaction. Thus, what is desired is drastically to increase the rate of interaction between the programmer and the computer without large economic loss and also to make each interaction more meaningful by extensive and complex system programming to assist in the man-computer communication.

In addition to allowing the development of usable and sophisticated debugging techniques, an efficient time-sharing system should make feasible a number of relatively new computer applications which can be implemented only at great cost in a conventional system. Any problem requiring a high degree of intermixture of computation and communication on a real-time basis should readily lend itself to time-sharing techniques. Examples of this type of application include: decision-tree problems; real-time management problems (airline reservations, hospital administration, etc.); gaming problems; sociological experiments; 1