fchk <filename>

Checks to see whether an image tag has been recorded in the file log.
This is used as an argument for an if statement. If the image has been loaded and may be used in-game, returns true. If not, or if the filename was incorrect, returns false.
ld c,":a;test.bmp",1
if fchk ":a;test.bmp" ;returns true
if fchk "test.bmp" @;returns false