;INPUT: DS:SI = BASE ADDR. OF STRING
;TYPICALLY, MS-DOS USES $ TO TERMINATE STRINGS.
GetStringLength:
xor cx,cx      ;this takes fewer bytes to encode than "mov cx,0"
cld            ;makes string functions post-inc rather than post-dec.

loop_GetStringLength:
lodsb          ;equivalent of "mov al,[ds:si],inc si" except this doesn't alter the flags.
cmp '$'
je done        ;if equal, we're finished.
inc cx         ;add 1 to length counter. A null string will have a length of zero.
jmp loop_GetStringLength

done:
ret