Assembly Language Programming - Fundamentals of Computer Organization and Architecture - page 54

the CX register and branch if the result is not zero. The addressing mode used to
access the array List [BX þ 1] is called based addressing mode.

MOV CX, 1000 ; Counter ¼ CX 1000

MOV BX, Offset
LIST

;BX pointer to LIST

MOV SI, 0 ; SI used as an index

MOV AX, VAL ; AX VAL

CALL SEARCH

; Test FLAG to check whether value found

.....

SEARCH PROC NEAR

; FLAG 0

MOV FLAG, 0

Next: CMP AX, [BX þ SI] ;Compare current value to VAL

JE Found ;Branch if equal

ADD SI, 2 ; SI SI þ 2, next value

LOOP Next ;Go to next value

JMP Not_Found
Found: MOV FLAG, 1 ;Indicate value found
MOV POSITION, SI ;Return index of value in List
Not_Found: RET

SEARCH ENDP

Example 5 This is the same as Example 4 but using the stack features of the X86.

PUSH DS ;See Table 3.9

MOV CX, 1000 ;Counter ¼ CX 1000

MOV BX, OFFSET LIST ;Point to beginning of LIST

PUSH BX
PUSH VAL ;VAL is a word variable

CALL SEARCH

;Test FLAG to check whether value found
;If found get index from SI register
using
POP SI

.....

SEARCH PROC NEAR

POP TEMP ;Save IP

POP AX ;AX VAL. Value to search for

POP SI ;SI OFFSET LIST and let BX ¼ SI