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The UNIX system begins to take shape
What Thompson had on the PDP-7 was a system, but not really an operating system.
So during the summer of 1969, Thompson began implementing the paper file system, which Ritchie liked to refer to as the "chalk file system," since it emerged from countless discussions at chalkboards in the Computing Science Research Center.
"I allocated a week each to the operating system, the shell, the editor, and the assembler to reproduce itself...", Thompson explained.
He first worked out the requirements for an operating system, in particular the notion of processes. Then he developed a small set of user-level utilities: the means to copy, print, delete and edit files. And he developed a command interpreter, or shell.
Next: It looked like an operating system, almost
![[ UNIX building blocks ]](images/86-300838-EM.jpeg)