Work sheet 1
Birth of the Unix Time-Sharing System
You are required to submit your answers in the acompanying assignment as you are working through this worksheet.
A. From batch processing to time-sharing systems
Until into the 60s, most computers were single-user systems. The computers were already very fast compared to human calculations but the programs have to be loaded in to the computer either in tapes or as staples of punch cards. This made it essential that a running program, called a job, has to be either finished or aborted before moving on to the next job. It was not possible stop a job half-way and to come back to where it was stopped.
In the early 60s researchers from the MIT and the AT&T Bell Labs came up with the revolutionary idea of the console. A console was basically a typewriter which transferred the keys that were pressed on it as electrical signals to the computer. This made a big difference. Now many users could submit their jobs to the computer at the same time. Since the computer can not run two programs at the same time, this meant that there has to be a central program coordinating the jobs. This is the 'supervisor' Prof. Corbató is talking about in the next video. Although the terminals of that time have vanished you might be surprised to learn that what Prof. Corbató says is still valid for today's operating systems.
1963 Timesharing explained by MIT (Part 1 of 2) (14:33 min)
M. I. T. Science Reporter John Fitch talking to Prof. Fernando José "Corby" Corbató
B. What is an Operating System?
Your text book might say, "An operating system is a software platform upon which programs may be run". That is all very well to say that, but what does that actually mean? The following video gives an answer for the layman.
Linux and Unix basics: What is UNIX? (7:16 min)
C. What is Unix?
The MULTICS operating system was put into commercial use at General Electric but not at Bell Labs. Two Bell Labs engineers from the MULTICS team, Ken Thompson and Dennis Ritchie, started working on a new operating system from the lessons they've learnt. They named their work Unics (Uniplexed Information and Computing Service) to mimik MULTICS. The name then evolved to Unix, allegedly to save typing.
Thompson started implementing their ideas on a PDP-7. The language he used, other than the machine language, was called B. Ritchie found that B language is insufficient to write their operating system and produced a successor to B, called the C programming language. During 1973 they re-wrote Unix in C. The importance of this step can not be overestimated. For the first time they had a portable operating system. An operating system written to one hardware platform could be ported to another architecture without rewriting the whole software.
Initially Unix was more an academic exercise. Around 1974 Bell Labs gave the source code of Unix to US universities fpr free. Unix immediately found resonance in the Universities. In the same year Thompson and Ritchie published a highly influential paper describing the Unix system in the Communications of the ACM. During 1976-77 Thompson went for a six months sabbatical to Berkeley and taught Unix. Since the source code was included the academia has started enhancing the system.
The popularity of Unix had its down sides. All the big computer vendors at the time Sun, IBM, Hewlett-Packard, ... also aquired Unix and ported it to their machines. In doing so they also enhanced it in their own way, resulting in many incompatible versions of Unix. This was the time of the Unix wars.
By this time AT&T discovered the potential of Unix and registered it under UNIX and introduced an expensive accreditation procedure. Ironically, this was ths beginning of closed software. Untill then software were bundled to the hardware, i.e. no use without that partcular hardware. Unix was a the first hardware independent operating system.
Linux and Unix Basics : UNIX History (6:30 min)