Program Termination
===================
The usual way for a program to terminate is simply for its `main'
function to return. The "exit status value" returned from the `main'
function is used to report information back to the process's parent
process or shell.
A program can also terminate normally by calling the `exit' function.
In addition, programs can be terminated by signals; this is
discussed in more detail in Note:Signal Handling. The `abort'
function causes a signal that kills the program.