INT 2F - DOS 3.0+ internal - CHECKSUM MEMORY AX = 121Ch DS:SI -> start of memory to checksum CX = number of bytes DX = initial checksum SS = DOS DS (must be using a DOS internal stack) Return: AX, CX destroyed DX = checksum DS:SI -> first byte after checksummed range Notes: used by DOS to determine day count since 1980/1/1 given a date supported by DR DOS 5.0+ SeeAlso: AX=121Dh