I'm a beginner in assembly language and I have to find a solution fast.
The thing is I have to read a number from the person (3 digits), convert it to an integer and compare it to two values.
The problem is that after converting the comparisons are off, sometimes the result is correct sometimes it's not.
pile segment para stack 'pile'
db 256 dup (0)
pile ends
data segment
ageper db 4,5 dup(0)
bigg db 13,10,"bigger than 146 ",13,10,"$"
lesss db 13,10,"less than 0 ",13,10,"$"
right db 13,10,"correct number 123 ",13,10,"$"
theint db 0
exacnumber db 123
data ends
code segment
main proc far
assume cs:code
assume ds:data
assume ss:pile
mov ax,data
mov ds,ax
mov ah,0ah
lea dx,ageper
int 21h
mov ch,0
cmp ageper[4],0
jz phase2
mov ah,ageper[4]
sub ah,48
add theint,ah
phase2:
mov cl,10
cmp ageper[3],0
jz phase3
mov ah,ageper[3]
sub ah,48
mov al,ah
mul cl
add theint,al
phase3:
mov cl,100
cmp ageper[2],0
jz phase4
mov ah,ageper[2]
sub ah,48
mov al,ah
mul cl
add theint,al
phase4:
cmp theint,123
je yes
cmp theint,130
jg big
cmp theint,0
jl less
jmp ending
big:
mov ah,09h
lea dx,bigg
int 21h
jmp ending
yes:
mov ah,09h
lea dx,right
int 21h
jmp ending
less:
mov ah,09h
lea dx,lesss
int 21h
ending:
mov ageper,20
mov ageper[1],20
mov ah,02
lea dx,theint
int 21h
mov ah,4ch
int 21h
main endp
code ends
end main
cmp ageper[4],0 jz phase2 ... cmp ageper[3],0 jz phase3 ... cmp ageper[2],0 jz phase4
Your program performs erratically because you're not interpreting the input correctly!
The simple 3-digit input recieved from DOS need not be checked for the number zero like you did. Just remove those 3 cmp's and jz's.
Another small logical error is that when the number is bigger than 130, you report it as being bigger than 146.
mov ageper,20 mov ageper[1],20
These instruction make no sense!
mov ah,02 lea dx,theint int 21h
Here you're confused in the use of the correct DOS function. Function 02h uses the DL register, function 09h uses the DX register. Please look it up in your manual.
To address the issue reported by @Michael (to deal with 3-digit numbers from 256 to 999), define the theint variable as word and add to it as shown below:
theint dw 0
mov ch, 0
mov cl, ageper[4]
sub cl, 48
mov theint, cx <<< Use MOV the first time!
phase2:
mov cl, 10
mov al, ageper[3]
sub al, 48
mul cl
add theint, ax <<< Add AX in stead of AH
phase3:
mov cl, 100
mov al, ageper[2]
sub al, 48
mul cl
add theint, ax <<< Add AX in stead of AH