system_status

system_status is a compiler-defined global variable. It exists entirely to hold values returned from system or resource calls. If a system function is not available on the current interpreter being used, the system call will set system_status as -1. If there is no problem, system_status is set to 0. Some uses:

1. In a game with graphics, if the picture doesn’t work, you could print some placeholder text like “[This is supposed to be a picture of a turtle, but this interpreter doesn’t support graphics]”
2. Two of Mike Snyder’s games, Distress and Tales of the Traveling Swordsman, call system(PAUSE_100TH_SECOND) as a glk check

!----------------------------------------------------------------------------
! detect for whether or not this is a GLK port.
routine is_glk_port
{
    system(PAUSE_100TH_SECOND)
    if (system_status = 0) {
        return false
    } else {
        return true
    }
}

(Glk.h, on the other hand, checks “glk-ness” by checking display.windowlines.)

system_status values

Besides 0 and -1, system_status can be set to several other values, depending. Here is the full range (keep in mind that many of these are used for resource files):

Value	Constant Name (as defined by “system.h” or “resources.h”)	Meaning
0	STAT_NOERROR	System or resource call worked
-1	STAT_UNAVAILABLE	Function not available on current interpreter
101	STAT_NOFILE	File wasn’t found
102	STAT_NORESOURCE	Resource wasn’t found
103	STAT_LOADERROR	File found but did not load properly