How to make a loop in x86 assembly language

Question

I have written the code so far as    code  main  Clrscr    mov dh 10             row 10    mov dl 20             column 20    call Gotoxy           locate cursor    PromptForIntegers        WriteString        display string     ReadInt            input integer   ArraySum      WriteString        display string     WriteInt           display integer  DisplaySum  ENDP  END main   How do I get it to repeat the same steps three times using a loop  clearing the screen after each loop iteration

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model small  stack 100h  code  Main proc Mov cx   30     that number control the loop 30 means the loop will   excite 30 time  Ioopfront  Mov ah   1 Int 21h  Loop loopfront     this cod will take 30 character

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You need to use conditional jmp commands  This isn t the same syntax as you re using  looks like MASM  but using GAS here s an example from some code I wrote to calculate gcd   gcd alg      subl     ecx   eax         a   a - c        cmpl     0   eax           if a    0        je      gcd done           jump to end        cmpl     ecx   eax         if a  lt  c        jl      gcd preswap        swap and start over        jmp     gcd alg            keep subtracting      Basically  I compare two registers with the cmpl instruction  compare long   If it is less the JL  jump less  instruction jumps to the preswap location  otherwise it jumps back to the same label   As for clearing the screen  that depends on the system you re using

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I was looking for same answer  amp  found this info from wiki useful  Loop Instructions  The loop instruction decrements ECX and jumps to the address specified by arg unless decrementing ECX caused its value to become zero  For example    mov ecx  5  start loop     the code here would be executed 5 times  loop start loop   loop does not set any flags   loopx arg  These loop instructions decrement ECX and jump to the address specified by arg if their condition is satisfied  that is  a specific flag is set   unless decrementing ECX caused its value to become zero    loope loop if equal loopne loop if not equal loopnz loop if not zero loopz loop if zero   Source  X86 Assembly  Control Flow

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Use the CX register to count the loops   mov cx  3 startloop     cmp cx  0    jz endofloop    push cx loopy     Call ClrScr    pop cx    dec cx    jmp startloop endofloop       Loop ended      Do what ever you have to do here   This simply loops around 3 times calling ClrScr  pushing the CX register onto the stack  comparing to 0  jumping if ZeroFlag is set then jump to endofloop  Notice how the contents of CX is pushed popped on off the stack to maintain the flow of the loop

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Yet another method is using the LOOP instruction   mov  cx  3  myloop        Your loop content      loop myloop   The loop instruction automatically decrements cx  and only jumps if cx    0   There are also LOOPE  and LOOPNE variants  if you want to do some additional check for your loop to break out early   If you want to modify cx during your loop  make sure to push it onto the stack before the loop content  and pop it off after   mov  cx  3  myloop      push cx       Your loop content     pop  cx      loop myloop

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mov cx 3  loopstart     do stuff    dec cx           Note   decrementing cx and jumping on result is    jnz loopstart    much faster on Intel  and possibly AMD as I haven t                     tested in maybe 12 years  rather than using loop loopstart

[loops] How to make a loop in x86 assembly language?

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