In this documentation cc -Aa will be used. All C programs need a main function where execution begins. Then a function mean is called that calculates the mean of the arguments given it. The on-line manual page describes printf fully. The variables that these format strings refer to are added to the argument list of printf .
C programs stop when The end of main is reached.
The program is interrupted in some way. Typing test is likely to run the test facility built into the shell, producing no input, rather than the user's program.