The SaveScreen function saves the current video context.
AX
Specifies the size in bytes of the saved video context.
DS
Specifies the segment address of the grabber (CS and DS registers are equal).
ES:DI
Points to the saved video context.
The return value is a cleared carry flag if successful. Otherwise, the carry flag is set to indicate an error.
Windows guarantees that the offset portion of the screen save area (the DI register) will always be zero.