[NASM] Need help! Print prime numbers to n

[fliego]

Hi!

User input num, then program have to print all prime numbers from 0 to n.
No errors through compile, but no any print info
Ubuntu x86, nasm





<sub>global _start

section .data
msg db "Hello"

section .bss
num resb 4

section .text
_start:
        call input
        mov eax,num
        push eax
        call isPrime
        push edx
        call print
        call exit
exit:
        mov eax,1
        mov ebx,0
        int 0x80
        ret
print:
        push ebp
        mov ebp,esp
        mov ecx,[ebp+8]
        mov eax,4
        mov ebx,1
        mov edx,4
        int 0x80
        pop ebp
        ret
input:
        push ebp
        mov ebp,esp
        mov eax,3
        mov ebx,0
        mov ecx,num
        mov edx,4
        int 80h
        pop ebp
        ret
isPrime:
        push ebp
        mov ebp,esp
        mov eax,[ebp+8]
        mov edx,0
        cmp eax,0
        je .mEx
        cmp eax,1
        je .mEx
        cmp eax,2
        je .mExTwoOrThree
        cmp eax,3
        je .mExTwoOrThree
        mov ebx,2
        mov ecx,eax
        shr ecx,1
.mMain:
        push eax
        mov edx,0
        div ebx
        pop eax
        cmp edx,0
        jne .mZR
        mov edx,0
        jmp .mEx
.mZR:
        cmp ebx,ecx
        je .mEx
        inc ebx
        jmp .mMain
.mExTwoOrThree:
        mov edx,1
.mEx:
        pop ebp
        ret</sub>

[Frank Kotler]

Hi fliego,

Thanks for joining us.

Think about what you're actually asking to have printed. Your "print" routine expects the address of four characters to print on the stack. I'm not sure what "isPrime" returns in edx (zero or non-zero?), but it isn't likely to be a valid address of a string to print. So no output.

We can't really input or print "numbers". We read characters (hopefully representing a number), and need to convert that to a number before we can use it for anything. Likewise when we get a number (some prime less than n), we need to convert that to characters we can write.

There are different ways to do that. "Just call scanf/printf" is easy - I consider it "overkill" just to read/write an integer. There are a number of libraries that include such routines written in assembly. Our user "stressful" has recently posted such a library (not in the form of a literal "library") that looks quite nice:
http://forum.nasm.us/index.php?topic=2062.0

Or you can write your own routines to convert text-to-number and number-to-text. I consider this "a good exercise", but it's been done before... It's about the most frequently asked question of all time, so you should be able to find plenty of examples to "go by" (or swipe). Hmmm... here's an example that seems to do exactly what you want (although more complicated, perhaps):
http://forum.nasm.us/index.php?topic=1289.msg5158#msg5158

In any case, you need to pass "print" the address of some text. Your "input" routine gets text, and you're passing that to "isPrime". That probably isn't going to work as intended either. If you continue to have trouble, let us know where you're stuck, and we'll try to help.

Best,
Frank

Edit: here's some more discussion of the subject:
http://forum.nasm.us/index.php?topic=1514.msg6228#msg6228

[nasm32]

I remember, one time I taught a class of girls about prime numbers. When girls get to learn about prime numbers they often get a chance to teach it away also. After so many years of being a teacher, you'll notice that when girls get to know about boystuff, they often also compete with the opposite sex. It's unmistakable. I did not ever want to have anything to do with that, so I asked them to please leave me out of it.

When that being said, one of the things I like and don't like about nasm and fasm is that nasm is so damn liberal in its design. fasm is so narrowed down and almost "closed up". fasm, to me, is like fascism. It seems as if the author of it want it to evolve into a hll language.

[fliego]

Thank you very much, Frank! :}

Seems like program do what I desided it to:

<sup>%include "/home/student/stud_io.inc"

section .bss
digit resb 1

section .data
new_line db 10,13

section .text
global _start
_start:
   print_string "N = "
   call read_number
   mov ecx,eax
   mov eax,1
main_loop:
   inc eax
   cmp eax,ecx
   jnl exit
   mov ebx,2
is_prime:
   cmp eax,ebx ; haltura
   je print_prime
   push eax
   xor edx,edx
   div ebx
   pop eax
   test edx,edx
   jz not_prime
   inc ebx
   jmp is_prime
not_prime:
   jmp main_loop
print_prime:
   push eax
   call print_number
   print_string " "
   jmp main_loop
exit:
   mov eax,4
   mov ebx,1
   mov ecx,new_line
   mov edx,2
   int 80h
   
   syscall_exit 0

read_number:
   xor eax,eax
   mov ebx,10
   mov [digit],byte 0x30

.read_digit:
   mul ebx
   add eax,[digit]
   sub eax,0x30
   call read_digit
   cmp [digit],byte 0xA
   jne .read_digit
   ret

read_digit:
   pusha

   mov eax,3
   mov ebx,0
   mov ecx,digit
   mov edx,1
   int 80h

   popa
   ret

print_number:
   mov eax,[esp + 4]
   pusha
   mov ebx,10
   xor ecx,ecx

.push_digit:
   xor edx,edx
   div ebx
   push dx
   inc ecx
   test eax,eax
   jnz .push_digit

.print_digit:
   pop ax
   call print_digit
   loop .print_digit
   popa
   ret

print_digit:
   pusha
   mov [digit],al
   add [digit],byte 0x30

   mov eax,4
   mov ebx,1
   mov ecx,digit
   mov edx,1
   int 80h

   popa
   ret</sup>