mov ax, 1000h ;Get SHARE.EXE Installed State
int 2Fh ;Multiplex Interrupt
cmp al, 0FFh ;0FFh means installed
Get SHARE.EXE Installed State (Interrupt 2Fh Function 1000h) determines whether the resident portion of the Share program has been loaded.
This function has no parameters.
The AL register contains 0FFh if the Share program has been loaded or 00h if it has not.
Some operating environments, such as Windows, intercept this multiplex interrupt and always return a nonzero value whether the Share program is loaded or not. To determine whether file sharing is available, a program should check for error values upon returning from carrying out a file-sharing function, such as Lock/Unlock File (Interrupt 21h Function 5Ch).
Interrupt 21h Function 5Ch Lock/Unlock File