The Algol 68 program can report an exit status to the operating system once they stop running. The exit status reported by default is zero, which corresponds to success.
= (int status) ¶Procedure that sets the exit status to report to the operating system once the program stop executing. The default exit status is 0 which, by convention, is interpreted by POSIX systems as success. A value different to zero is interpreted as an error status. This procedure can be invoked more than one, the previous exit status being overwritten.