The function system(char *s) executes the command contained in the character string s, then resumes execution of the current program. The contents of s depend strongly on the local operating system. As a trivial example, on UNIX systems, the statement
system(”date”);
causes the program date to be run; it prints the date and time of day on the standard output. system returns a system-dependent integer status from the command executed. In the UNIX system, the status return is the value returned by exit.