why the code return 23

Question

In the tutorials of directfb, the link is Simple fullscreen application that draws a horizontal line

My question is why it return 23?

in ASCII, 23 means ETB, what's the reason to return ETB? It confuses me.

Thanks.

Answer 1

The main function of a C or C++ program should return an exit code to the operating system or its parent process. In that case, 23 is the exit code returned by this program.

Typically, returning 0 means success. Depending on the system, other exit codes may be "reserved" for special purposes, that is, they still can be used but may confuse the OS into believing the program ended incorrectly.

Exit codes are useful when running external programs and checking whether or not they completed successfully, or had any specific response. You'll have to refer to the specific program documentation to understand what each exit code means.