Unix History & Characteristics


UNIX was developed at AT&T's Bell Laboratory 1969 Ken Thompson developed UNIX
Dennis Ritchie modified and developed C Ritchie and Thompson rewrote UNIX in C. By 1980 the entire UNIX is rewritten and could be moved on to any machine.


Portability ability of software that operates on one machine to operate on another. Decrease programming costs.

Multiuser More than one user can access the same data at the same time. Less expensive than equivalent number of single users.

Multitasking Given user can do more than one task at the same time. Some tasks can be placed in the background. Example: Sorting. Some tasks that require human intervention can be executed in the foreground. The more background tasks the slower is the system response.

The UNIX file system Allows a hierarchical structure. Can create as many directories as needed. Access control to files. Allows file and record locking.

Utilities and tools Utilities are simple programs that do simple tasks. They are designed to do one job. They are non-interactive and are also called commands. Ex: telling you the current time and date Tools are more complex. They can do several tasks and are designed to be used interactively. Ex: UNIX mail program (tell UNIX what to do with the mail after reading it – save/delete/reply)

System security Give your password protection. Control access to individual files. Encryption of data files. System accounting functions useful for analysis of which user did what.