CODEWITHSUNDEEP
assemblyasciix86-64multiplicationfpu
Rijn
Rijn

Reputation: 15

Need help multiplying using FPU in x86 Assembly

Basically, I want to multiply a user inputted value by a set value. The code works when multiplying to user inputs together, however, if I preset 'number' to a value (ex: 6), it will not do the multiplication and returns 0.

_start:   
finit                           ; init. the float stack

output inprompt                 ; get radius number 
input  number, 12               ; get (ascii) value of this number
pushd  NEAR32 PTR number        ; push address of number
call   atofproc                 ; convert ASCII to float in ST

fld    st                       ; value1 in ST and ST(1)

mov number, 6

; If I substitute the line above by the two lines below, it works:
; output inprompt, 0
; input number, 12   

pushd  NEAR32 PTR number        ; push address of number
call   atofproc                 ; convert ASCII to float in ST

fmul                            ; value1*value2 in ST
fst   prod_real                 ; store result


push prod_real                  ; convert the results for printing

lea eax, sum_out                ; get the ASCII string address
push eax
call ftoaproc

output outprompt

Upvotes: 0

Views: 360

Answers (1)

Carey Gregory
Carey Gregory

Reputation: 6846

You're trying to convert 6 from ASCII to float, and 6 is a non-printable character in ASCII so it can't be converted to float. You need to change 6 to 54, which is the ASCII representation of the character '6'. Or you could pass the floating point constant 6.0 and delete the call to atofproc if you prefer.

Upvotes: 1

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