The UNIX operating system was developed in 1969 at Bell Laboratories. UNIX has continued to develop since its inception. AT&T, for example, released UNIX 4.0.
UNIX was designed to be a multiuser system (more than one user can connect to the host at one time), and it is used usually for multiuser systems and networks.
Because most engineers are more familiar with DOS (and Windows NT) than UNIX, this section presents some analogies to demonstrate the UNIX command structure.
The operating system DOS used in the early days is similar to UNIX in terms of architecture. For example, the command syntax to list the directories in DOS is dir, and in UNIX, it is ls.
Table 6-1 displays some of the common commands between UNIX and DOS.