How to print fibonacci series in assembly?

Question

I have tried to get the fibonnacci series up to a given number. But won't print correctly. Here is my code. num is the given number.

proc getFibo
        mov al,num

        mov cl,0
        mov bl,1

        mov dl,cl
        add dl,48
        mov ah,02h
        int 21h


        getNext:
            mov dl,bl
            add dl,48
            mov ah,02h
            int 21h

            add cl,bl

            mov dl,cl
            add dl,48
            mov ah,02h
            int 21h

            add bl,cl

            mov cl,bl
            add bl,1
            cmp bl,num
            jl getNext


        ret
    endp

Someone help me please.Thanks in advance..!

Answer 1

proc getFibo
        mov al,f1
        mov bl,f2

    ;mov cl,count
    ;cmp cl,num
    ;je exitFibo

    mov dl,al
    add dl,48
    mov ah,02h
    int 21h

    mov cl,count
    add cl,1
    mov count,cl

    mov dl,bl
    add dl,48
    mov ah,02h
    int 21h

    mov cl,count
    add cl,1
    mov count,cl

    calcFibo:
        mov al,f1
        add al,f2
        mov f1,al

        mov dl,f1
        add dl,48
        mov ah,02h
        int 21h

        mov cl,count
        add cl,1
        mov count,cl

        mov cl,count
        cmp cl,num
        je exitFibo

        mov bl,f2
        add bl,f1
        mov f2,bl

        mov dl,f2
        add dl,48
        mov ah,02h
        int 21h

        mov cl,count
        add cl,1
        mov count,cl

        mov cl,count
        cmp cl,num
        je exitFibo

        jmp calcFibo

    exitFibo:
    ret
endp

I have found the answer. Thank u all.

Answer 2

The loop condition at the end is incorrect:

mov cl,bl   # this is skipping a value in the F-series. F(i-2) == F(i-1)
add bl,1    # this is just wrong for the F-series. F(i) = F(i-1) + 1 + F(i-2)

cmp bl,num  # ok - `bl` is the next value printed if < num.
jl getNext

Those first two lines should go. If your intent was to loop if <= num, use: jle. Since you're only printing a character, this isn't going to work correctly after: 0112358

Answer 3

Won't take you long to run out of register space on a 16 bit system...

I've updated my answer, it's still not perfect though

 mov bp,sp                                 
 mov ax,1                        
 mov bx,2                        

 .again     ;fibonacci bit                      
 add ax,bx                       
 push ax                         
 add bx,ax                       
 jc putnumsonstack  ;finishes when the fibonacci number bigger than the register
 push bx                         
 jmp again                       

 .putnumsonstack  ;Turns hex into decimal                
 mov bx,A         ;and puts individual decimal numbers onto stack               
 .again2                          
 cmp ax,0         ;tells you the division by A is finished               
 jz print         ;and the decimal number is ready to print 
 div bx           ;divide a hex num by hex-A and the dx carry gets the decimal 
 add dl,30        ;The dx carry is what we print out, so we add hex-30              
 push dx          ;and put it on the stack for printing              
 mov dx,0         ;then clear dx for the next DIV bx               
 jmp again2                      


 .print           ;prints out the decimal numbers               
 pop ax           ;strips the stack back towards the next hex number
 cmp ah,0                 ;tells you the decimals are all printed       
 jnz putnumsonstack       ;jumps to the next decimal numbers stackload       
 ;PRINT OUT AL HERE              
 cmp sp,bp                                  
 jae finished                             
 jmp print                       

 .finished                            

Answer 4

Or try the following code which produces the results shown below:

my $N = 11;                                 # The number of Fibonacci numbers to generate
  Mov r13, 0;                                 # First  Fibonacci number
  Mov r14, 1;                                 # Second Fibonacci
  PrintOutStringNL " i   Fibonacci";          # The title of the piece

  V(N => $N)->for(sub                         # Generate each fionacci numbr by adding tehtwo previous ones together
   {my ($index, $start, $next, $end) = @_;
    $index->outRightInDec(2);                 # Index
    Mov rax, r13; PrintOutRaxRightInDecNL 12; # Fibonacci number at this index

    Mov r15, r14;                             # Next number is the sum of the two previous ones
    Add r15, r13;

    Mov r13, r14;                             # Move up
    Mov r14, r15;
   });

  ok Assemble eq => <<END;                    # Assemble and show expected output
 i   Fibonacci
 0           0
 1           1
 2           1
 3           2
 4           3
 5           5
 6           8
 7          13
 8          21
 9          34
10          55
END

available at: https://github.com/philiprbrenan/NasmX86#print-some-fibonacci-numbers-from-assembly-code-using-nasm---the-netwide-assember-and-perl