Consider the following array with the contents given (you have to declare it in your program):
5 9 11 16 20 25 19 7 30 13
Write an assembly program using index addressing to convert each of the even numbers in the array to its next higher odd numbers and each of the odd numbers in the array to its immediate lower even numbers. then add all modified numbers in the array and store result in a memory location 'RESULT'. consider each of the element is of WORD size
Here is an assembly program that uses index addressing to convert the numbers in the array according to the given requirements and stores the result in a memory location called 'RESULT':
```assembly
ORG 1000h
SECTION .data
array DW 5, 9, 11, 16, 20, 25, 19, 7, 30, 13
array_size equ ($ - array) / 2
SECTION .text
GLOBAL _start
_start:
mov cx, array_size ; initialize loop counter with the size of the array
mov bx, 0 ; initialize sum of modified numbers to 0
lea si, array ; load array base address into SI register
loop_start:
mov ax, [si] ; load the current element from the array into AX
test ax, 1 ; check if the number is odd (if the least significant bit is set)
jnz odd_number ; jump to odd_number if the number is odd
add ax, 1 ; if the number is even, add 1 to convert it to the next higher odd number
jmp next_iteration ; jump to the next iteration of the loop
odd_number:
sub ax, 1 ; if the number is odd, subtract 1 to convert it to the immediate lower even number
next_iteration:
add bx, ax ; add the current modified number to the sum in BX
add si, 2 ; move to the next element in the array by adding 2 to SI (because each element is WORD size)
loop loop_start ; decrement the loop counter and jump to loop_start if it is not zero
mov WORD [RESULT], bx ; store the sum of modified numbers in memory location 'RESULT'
; Exit program
mov eax, 1 ; prepare for exit syscall
xor ebx, ebx ; exit code 0
int 0x80
SECTION .bss
RESULT resw 1
```
Note:
- This program assumes the NASM assembly syntax and is for x86 architecture.
- The array is declared in the .data section with the given contents.
- 'array_size' is a constant that holds the size of the array (number of elements).
- The loop iterates for each element of the array.
- The current element is loaded into AX using index addressing (`mov ax, [si]`).
- The `test` instruction checks if the number is odd by checking the least significant bit.
- If the number is even, 1 is added to convert it to the next higher odd number.
- If the number is odd, 1 is subtracted to convert it to the immediate lower even number.
- The modified number is added to the sum in BX.
- The loop continues until all elements of the array have been processed.
- Finally, the sum of modified numbers in BX is stored in the memory location 'RESULT' using `mov WORD [RESULT], bx`.
- The program then exits with an exit code 0 using the exit syscall.
Sure! Here's a step-by-step breakdown of the assembly program to achieve the desired task:
Step 1: Define the array with the given contents
- Declare a memory block to store the array elements, each of WORD size (2 bytes). Let's assume it starts at memory location 'ARRAY'.
- Initialize the array with the given contents: 5 9 11 16 20 25 19 7 30 13
Step 2: Initialize the index register with 0
- Assume the index register is 'R1' and set 'R1' to 0.
Step 3: Start a loop to iterate through the array
- Use a loop construct to repeat the following steps from Step 4 to Step 9 until the end of the array is reached.
Step 4: Check if the current element is even
- Load the content of the array element at the current index into a register, let's say 'R0'.
- Use the 'AND' instruction to check if the lowest bit of 'R0' is 1, indicating an odd number.
eg. AND R2, R0, #1
(This will set the 'R2' register with the result of the bitwise AND operation between 'R0' and '1').
Step 5: If the current element is even, convert it to the next higher odd number
- If the value in 'R2' is 0, it means the current element is even.
- Increment the value in 'R0' by 1 to convert it to the next higher odd number.
eg. ADD R0, R0, #1
Step 6: If the current element is odd, convert it to the immediate lower even number
- If the value in 'R2' is 1, it means the current element is odd.
- Decrement the value in 'R0' by 1 to convert it to the immediate lower even number.
eg. SUB R0, R0, #1
Step 7: Add the modified element to a running sum
- Use an accumulator register, let's say 'R3', to store the running sum.
- Add the value in 'R0' to the value in 'R3' using the 'ADD' instruction.
eg. ADD R3, R3, R0
Step 8: Store the modified element back into the array
- Store the modified value in 'R0' back into the array at the current index.
- Use indexed addressing to access the array element at the current index.
eg. STR R0, [ARRAY, R1, LSL #1]
(This will store the content of 'R0' at the memory location 'ARRAY + (2 * R1)').
Step 9: Increment the index and check the loop condition
- Increment the value in 'R1' by 1 to move to the next element in the array.
- Check the loop condition, if the end of the array is not reached, go back to Step 4.
- Otherwise, exit the loop.
Step 10: Store the final result in memory location 'RESULT'
- Store the value in 'R3', which contains the running sum, into the memory location 'RESULT'.
eg. STR R3, [RESULT]
That's it! The assembly program is complete.