Question

Code written in NASM

Function called findLargest
Write a function called findLargest that receives two parameters: an unsigned doubleword array and the length of the array. The function must return the value of the largest array member in eax. Preserve all registers (except eax) that are modified by the function. Write a test program in main that calls findLargest three times, each call using a different array with different lengths.

Function called countHits
Write a function called named countHits that takes as parameters two arrays of unsigned doublewords, and a third parameter that indicates the length of the two arrays (they are the same length). For each element in the first array, x(i), if the corresponding element in the second array, y(i) is equal, increment a count. After comparing the arrays, return a count of the number of matching array elements in registers eax. Write a test program in main that calls your function and passes the memory addresses of the arrays and the length of the arrays. Be sure to save and restore any registers, other than eax, that are changed by your procedure.

Answer 1

Code For Function called findLargest:

INCLUDE Irvine32.inc

.data

numberrange DWORD 50, 100, -4, -5, 2, 5, 101, 34, 23, 45

numberrange1 DWORD 20, 30, 40, 50

numberrange2 DWORD - 2, -5, 2, 7, 3, 10, 15, 20, 5, 6, 21, 0, 4, -5, 31, 33

largernum DWORD 0

.code

Findlargest Proto, num:DWORD, num1 : DWORD, num2 : DWORD

main PROC

invoke FindLargest, ADDR numberrange, LENGTHOF numberrange, SIZEOF numberrange

invoke FindLargest, ADDR numberrange1, LENGTHOF numberrange1, SIZEOF numberrange1

invoke FindLargest, ADDR numberrange2, LENGTHOF numberrange2, SIZEOF numberrange2

exit

main ENDP

LargestMember PROC

mov largernum, [esi]

mov eax, [esi+4]

L1:

.if largernum < [esi]

mov largernum, [esi]

.endif

add esi, 4

inc ecx

loop l1

ret

LargestMember ENDP

END MAIN

Code for countHits:

INCLUDE Irvine32.inc
countHits PROTO, Pointer_Arr1:PTR SDWORD, Pointer_Arr2:PTR SDWORD, Arr_Size:DWORD, d:DWORD

.data
First_Arr SDWORD 1,2,3,4,5
First_Arr1 SDWORD 6,7,8,9,10
Second_Arr SDWORD 11,12,13,14,15
Second_Arr1 SDWORD 16,17,18,19,20
count DWORD ?,0
difference1 DWORD 11
difference2 DWORD 0
  
.code
main PROC   
INVOKE countHits, ADDR First_Arr, ADDR First_Arr1, LENGTHOFFirst_Arr, difference1
call WriteInt
call Crlf
INVOKE countHits, ADDR Second_Arr, ADDR Second_Arr1, LENGTHOFSecond_Arr, difference2
call WriteInt ;Library Function to display a message in Irvine32
call Crlf ;Library Function
exit
main ENDP

countHits PROC USES edx ebx edi esi ecx, Pointer_Arr1:PTR SDWORD, Pointer_Arr2:PTR SDWORD, Arr_Size:DWORD, d:DWORD
mov esi,Pointer_Arr1 ;copy the address of source address in extended source index register.
mov edi,Pointer_Arr2 ;copy the destination address in extended destination index register.
mov ecx,Arr_Size; the size of the array is copied into the c register.
Lable1: mov ebx,0 ;zero is stored in the b register.
mov ebx,[esi] ;The content of source index register is stored in b register.
mov edx,0;zero is stored in the d register.
mov edx,[edi];The content of source index register is stored in b register.
IF ebx > edx; compare the content of b and d register.
mov eax,ebx;if the content of b register is greater than d register, store the content of b register into a register.
sub eax,edx ; Subtract the content of d register from a register, the result is stored in a register.
ELSE
mov eax,edx; if the content of b register is smaller than d register, store the content of d register into a register.
sub eax,ebx ; Subtract the content of b register from a register, the result is stored in a register.
ENDIF
IF (eax <= d);If the content of a register is greater or equal to difference
inc count; Increment the counter
ENDIF
add esi, SIZEOF SDWORD ;Add the content of SIZEOF SDWORD to source index register.
add edi, SIZEOF SDWORD;Add the content of SIZEOF SDWORD to destination index register.
loop Lable1;Go to loop Lable1
mov eax,0; zero is stored in the a register.
mov eax,count;the content of count is stored in a register.
mov count,0; zero is stored in the count register.
ret
countHits ENDP
END main

Code attached for both the function .Please let me know for clarifications .