z/OS XL C/C++ programs require that the standard streams, stdin, stdout, and stderr, be defined as either a file or a terminal. Many C functions use stdin, stdout, and stderr. For example:

• getchar() obtains a character from stdin.
• printf() writes output to stdout.
• perror() writes output to stderr.

(For more information about stdin, stdout, and stderr, see Understanding standard input, standard output, and standard error.)