The book is dedicated to the UNIX family of operating systems and contains information about the principles of organization, ideology and architecture that unite various versions of this operating system. The book discusses: the architecture of the UNIX kernel (input/output subsystems, memory and process management, as well as the file subsystem) , UNIX programming interface (system calls and basic library functions), user environment (shell, basic commands and utilities) and UNIX network support (TCP/IP family protocols, network subsystem architecture, socket programming interfaces and TLI). circle of users