Section 2: System Calls

The Xinu operating system kernel consists of a set of run-time procedures to implement operating system services on an LSI 11/2 microcomputer.  The system supports multiple processes, I/O, synchronization based on counting semaphores, preemptive scheduling, and communication with other machines.  Each page in this section describes a system routine that can be called by a user process. 

Each page describes one system call, giving the number and types of arguments that must be passed to the procedure under the heading "SYNOPSIS" (by giving their declaration in C syntax).  The heading "SEE ALSO" suggests the names of other system calls that may be related to the described function.  For example, the "SEE ALSO" entry for system call wait suggests that the programmer may want to look at the page for signal because both routines operate on semaphores. 

In general, Xinu blocks processes when requested services are not available.  Unless the manual page suggests otherwise, the programmer should assume that the process requesting system services may be delayed until the request can be satisfied.  For example, calling read may cause an arbitrary delay until data can be obtained from the device. 

December 01, 1986