Category: other operating systems
INT 21 - Concurrent DOS v3.2+ - INSTALLATION CHECK AX = 4451h Return: CF set if not Concurrent DOS AX = error code (see #01680 at AH=59h/BX=0000h) CF clear if successful AH = single-user/multiuser nature (see #01581) 10h single-user AL = operating system version ID (see #01580) 14h multiuser AL = operating system version ID (see #01579) Notes: as of Concurrent DOS/XM 5.0 (possibly earlier), the version is stored in the environment variable VER and the OS type in variable OS use this function if you are looking for multiuser capabilities, AX=4452h for single-user this function should never return the single-user values; however, an application should be prepared to accept single-user values, i.e. it should check the returned AH and AL separately CCI Multiuser DOS 7.22 returns AX=DX=1466h. DR DOS 3.31+ error returns with AX=0001h SeeAlso: AX=4452h,AX=4459h