Removing a character from a string in MASM

Question

I have to write a program that

• takes a string from the key board buffer and puts it into a character array
• asks for a character to remove
• removes the character from the character array while shifting everything else over

I want to use a stack to accomplish this. So here is my logic.

Starting from the end of the string compare that character with the character that is to be removed. If it isn't the character push it on to the stack. If it is ignore it and move on through the string. Then starting from the beginning pop everything into place.

I'm supposed to use a procedure to accomplish this. When I'm stepping through everything seems to be working ok until I attempt to leave the procedure and return to main. I'm fairly sure my logic in my procedure is the problem. Right now when I attempt to work with the string "The" and remove the e I get "he".

TITLE String Manipulation

INCLUDE Irvine32.inc
.data
prompt byte "Please enter a string to manipulate : ",0
prompt2 byte "Please enter a character to remove: ",0
answerMSG byte "The new string is: ",0
string   BYTE 51 DUP (0)
char        BYTE ?
byteCount   dword ?
.code
main PROC
call    clrscr
push    eax ;perserve the registers
push    ecx
push    edx
mov edx, OFFSET prompt  ;prints the prompt
call    writeString
mov edx, OFFSET string  ;moves the register to the first location for the string
mov ecx, SIZEOF string  ;Sets the max characters
call readString
mov byteCount,eax   ;places actual count into a counting register
call    crlf
mov edx, OFFSET prompt2 ;prints the prompt
call    writeString
mov edx, OFFSET char
mov ecx, 1
call    readString
call    clrscr
mov ecx,    byteCount
mov edx, OFFSET string
call stringMan
mov edx,    OFFSET string
call writeString
pop edx
pop ecx
pop eax
main ENDP
;
stringMan PROC USES eax ecx edx
mov eax,0
L1: 
    movzx   edx , string[ecx]
    cmp dl, char
    jz L2
    push    edx
    inc eax
    L2:
    mov string[ecx],0
    LOOP L1
mov ecx,eax
mov eax,0
L3:
    pop edx
    mov byte ptr string[eax],dl
    inc eax
    loop    L3
    ret
stringMan ENDP

END main

Figured it out.

Answer:

I was not dealing with getting a character from the console correctly. I also was not dealing with the case when ecx = 0. This is the first position of the character array. So I was not comparing the correct character, and not pushing the first character onto the array when necessary. I have fixed it by removing

mov edx, OFFSET char
mov ecx, 1
call    readString

and replacing it with

call readChar
mov  char,al

then adding this after the L1 loop.

movzx   edx , string[ecx]
cmp dl,char
jz  L4
push edx
inc eax
L4:

It now works as designed. I just have some formatting issues to clear up.

Answer 1

Answer:

I was not dealing with getting a character from the console correctly. I also was not dealing with the case when ecx = 0. This is the first position of the character array. So I was not comparing the correct character, and not pushing the first character onto the array when necessary. I have fixed it by removing

mov edx, OFFSET char
mov ecx, 1
call    readString

and replacing it with

call readChar
mov  char,al

then adding this after the L1 loop.

movzx   edx , string[ecx]
cmp dl,char
jz  L4
push edx
inc eax
L4:

It now works as designed. I just have some formatting issues to clear up.