History of Unix

1. 1964: AT&T Bell Labs, General Electric, and MIT wanted to create a multi-tasking, multi-user operating system.
   • Previous computers were single threading: one program at a time.
   • The new operating system named Multics (MULTiplexed Information and Computing Service)
   
   
2. Four years later, Bell Labs withdrew from the project, since it was able to support only 3-4 concurrent users.
   • The Multics team at Bell Labs missed the collaborative environment of all working in the same room.
   • Ken Thompson lost his game machine. (Space-travel simulation he developed on the Multics system.)
   • Thompson found an old PDP-7 computer and moved his code over to that.
   
   
3. The old Bell Labs Multics group starting developing code for the PDP computer.
   • This was the beginning of the Unix Operating System.
   • Brian Kernighan named the OS UNICS (UNiplexed Information and Computing Service).
   • In one month, Ken Thompson build the core of Unix.
   • Bell Labs' management asked about the new toy.
   • Thompson said they were building a text-processing system.
   
   
4. Management gave them a bigger computer.
   • Unix was written in PDP-7 assembly.
   • The group needed to transition the code from PDP-7 to the newer machine.
   • The group decided to rewrite Unix in the high-level language B (condensed BCPL), but B was too slow (interpreted language).
   
   
5. Dennis Ritchie created a new high-level language called C to rewrite Unix in.
   • Because Unix was written in a high-level language, it can be ported (moved) to other hardware platforms (computers with different CPUs, memory, and/or peripheral devices).
   • In the 1970s, Bell Labs was not allowed to sell software.
   
   
6. The team gave away copies of the source code for free.
   • Unix source code is still shared today in the form of Linux.
   • Unix and C became popular, because everyone could get it for free.
   • Giving away code necessitated writing documentation about the code.
   
   
7. The team created documentation to go with the code in the form of man pages.