I had a go at it, and tried:
section .data promptmsg: db 'Enter integer: ' msgsize: equ $-promptmsg section .bss ;creating variables to store input firstnum: resb 6 secondnum: resb 6 section .text global _start _start: xor eax, eax xor ebx, ebx xor ecx, ecx xor edx, edx mov eax, 4 ;system call to write mov ebx, 1 mov ecx, promptmsg mov edx, msgsize int 80h xor eax, eax xor ebx, ebx xor ecx, ecx xor edx, edx mov eax, 3 ;system call to read mov ebx, 0 mov ecx, firstnum mov edx, 6 int 80h push firstnum xor eax, eax xor ebx, ebx xor ecx, ecx xor edx, edx mov eax, 4 ;system call to write mov ebx, 1 mov ecx, promptmsg mov edx, msgsize int 80h xor eax, eax xor ebx, ebx xor ecx, ecx xor edx, edx mov eax, 3 ;system call to read mov ebx, 0 mov ecx, secondnum mov edx, 6 int 80h push secondnum xor eax, eax xor ebx, ebx xor ecx, ecx xor edx, edx pop eax pop ebx add eax, ebx ;attempt to add firstnum and secondnum and store in EAX push eax xor eax, eax xor ebx, ebx xor ecx, ecx xor edx, edx mov eax, 4 ;once again a system call to write mov ebx, 1 pop ecx mov edx, 7 int 80h xor eax, eax xor ebx, ebx xor ecx, ecx xor edx, edx mov eax, 1 ;exit safely and return 0 mov ebx, 0 int 80h
Sorry about all the XOR instructions, I just wanted to make sure registers were cleared before I used them for a system call, I’m still learning assembly and not sure about what instructions will render a register empty.
When I compile, link and run this I can enter the two integers only if I include the ENTER character, i.e. newline character. An integer can’t be added to it, so already that causes a problem. So when I enter both of them, I get no further output on the screen from the program, and the it just ends.
How can I correct it?
(Using C or C++ with ASM is not an option in this case.)
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Answer
It’s not about “correcting” your code as it is about writing a missing part of it.
You have to parse integers, ignoring separating whitespace. Add them, then convert a result into a string. Then output this string. Calling scanf or strtol or printf is probably inacceptable to you, as it’s using a standard C library.