Question

Write common assembly language (RISC) programs to a) sum the first n elements of an array A, and b) compute r = ab for unsigned integers a and b. Each program will consist of a driver and a subprogram. The drivers will 1) read one or more values from the keyboard, 2) call the subprogram, and 3) print a result. The subprograms must not: ● store into memory, ● use registers $1 – $9, or ● make system calls

Answer 1

Solution a) Assembly Code for sum of first n element from array: DATA arraỵ DW 100 DUP (2) ;declare array maximum size is 100 num DB DUP ?) declare Number sun DB DUP (?) . CODE mov ah, 4 system call code for int read INT 21H sub al, 30H mOv num, a mov ebx,0array offset mov ecx, [num] loop counter LOOP mov ah, 4 isystem call code for int read INT 21H sub al, 30H mov array[ebx], al save int in the array at offset ebx addi ebx, 4 increment the offset by 4 dec ecx idecrement the ecx counter inz LOOP jump to loop if not zero push array ¡push the array values ush num ¡push given num ca sumValue mov sum, eax save the sum in eax register int 21H for display the sum

ca sumValue mov sum, eax isave the sum in eax register int 21H for display the sum SumValue: push ebp mex ebp, esp mov eax, 0 save value of sum mov ebx, [ebp+4] load num mo ecx, Lebpt8]¡load the array base address loopsum: mov edx, [ecx] load array values add eax, edx add array element that is edx to eax addi ecx, 4 increment offset by 4 dec ebx inz loopSum mov esp, ebp pop ebp 2

b) Assemblv Code for r-a*b: DATA a DB DUP (?) declare a b DB DUP (?) declare b DB DUP (2) ;declare r . CODE mov ah, 4 system call code for read int a INT 21H sub al, 30H mOv aal mov ah, 4 system call code for read int b INT 21H sub al, 30H max b, al push a ¡push a value push b ¡push b value call MULTIPLY call MULTIPLY function mov [r], eax move the result r to eax int 21H for display MULTIPLY: push ebp mov ebp, esp mov eax, [ebp+4] load b value mul eax, ebx ; for r a* b that is eax = eax*ebx mav esp, ebp pop ebp ret
Copyable Code:

a)

.DATA
array DW 100 DUP (?) ;declare array maximum size is 100
num DB DUP(?) ;declare Number
sum DB DUP(?)
.CODE
mov ah, 4 ;system call code for int read
INT 21H   
sub al, 30H   
mov num, al
mov ebx,0 ; array offset
mov ecx,[num] ;loop counter
LOOP:
mov ah, 4 ;system call code for int read
INT 21H   
sub al, 30H   
mov array[ebx], al ;save int in the array at offset ebx
addi ebx, 4 ;increment the offset by 4
dec ecx ;decrement the ecx counter
jnz LOOP ;jump to loop if not zero
push array ;push the array values
push num ;push given num
call SumValue
mov sum, eax ;save the sum in eax register
int 21H ;for display the sum
SumValue:
push ebp
mov ebp, esp
mov eax, 0 ;save value of sum
mov ebx, [ebp+4] ;load num
mov ecx, [ebp+8] ;load the array base address
loopSum:
mov edx, [ecx] ;load array values
add eax,edx ;add array element that is edx to eax
addi ecx, 4 ;increment offset by 4
dec ebx
jnz loopSum
mov esp, ebp
pop ebp
ret

b)

.DATA
a DB DUP(?) ;declare a   
b DB DUP(?) ;declare b   
r DB DUP(?) ;declare r
.CODE
mov ah, 4 ;system call code for read int a
INT 21H   
sub al, 30H   
mov a, al
mov ah, 4 ;system call code for read int b
INT 21H   
sub al, 30H   
mov b, al
push a ;push a value
push b ;push b value
call MULTIPLY ;call MULTIPLY function
mov [r], eax ;move the result r to eax
int 21H ;for display
MULTIPLY:
push ebp
mov ebp, esp
mov eax, [ebp+4] ; load b value
mov ebx, [ebp+8] ; load a value
mul eax,ebx ;for r = a* b that is eax = eax*ebx
mov esp, ebp
pop ebp
ret