TITLE  Sum of a column in a 2-dimensional array  TEST_SUM.ASM
COMMENT |
        Objective: To demonstrate array index manipulation
                   in a two-dimensional array of integers.
            Input: None
|          Output: Displays the sum.
.MODEL SMALL
.STACK 100H
.DATA
NO_ROWS        EQU  5
NO_COLUMNS     EQU  3
NO_ROW_BYTES   EQU  NO_COLUMNS * 2  ; number of bytes per row
class_marks    DW   90,89,99
               DW   79,66,70
               DW   70,60,77
               DW   60,55,68
               DW   51,59,57

sum_msg        DB   'The sum of the last test marks is: ',0

.CODE
.486
INCLUDE io.mac
main    PROC
        .STARTUP
        mov     CX,NO_ROWS   ; loop iteration count
        sub     AX,AX        ; sum := 0
        ; ESI := index of class_marks[0,2]
        sub     EBX,EBX
        mov     ESI,NO_COLUMNS-1  
sum_loop:
        add     AX,class_marks[EBX+ESI*2]
        add     EBX,NO_ROW_BYTES
        loop    sum_loop
        
        PutStr  sum_msg
        PutInt  AX
        nwln
done:        
        .EXIT
main    ENDP
        END     main