This text is intended for the reader who can create directories, edit files, write a simple shell script, write a C program, or if you use UNIX and no longer get lost through the system. A concise coverage of the UNIX system which includes: utilities; administration; software development; networking; and internal operation. The text should help the reader solve many problems in: writing shell scripts that solve data manipulation tasks; how to connect your UNIX workstation to a network; how to use UNIX utilities to find "lost" files; create user accounts; manage a network computer with NFS, NIS and DNS; debug and monitor a network; efficiently develop software on UNIX systems; write a graphical program for the X Window System; and secure and monitor your UNIX system.