disassembled
Technical User
This is a program that is pretty much a memory dump, that asks the user for a segement (i.e. 000A), an address (i.e. 0000), and the number of bytes (i.e. 0016). The output looks like 000A:0000 bytes *ascii* and the next line has 000A:0010 bytes *ascii*, however on the last line of output, it seems to be placing excess zeros between the bytes and the ascii unless of course you choose 20 bytes. How can I get rid of these?
title Memory Dump memorydump.asm
dosseg ; Specifies to use a DOS segment
.286 ; Enables pentium instructions
.model small ; Uses small memory model
.stack 100h ; Identifies Stack Segment at offset 100 Hex
.data
EnterSegment db 'Please Enter the 4 Digit Segment: ','$'
EnterAddress db 'Please Enter the 4 Digit Address: ','$'
EnterNumByte db 'Please Enter the Number of Bytes: ','$'
ReturnString db 0ah, 0dh, '$'
ASCIITable db '0123456789ABCDEF'
Here db 4 dup (' ')
SegmentToUse dw 1 ; Holds segment entered by user
AddressToUse dw 1 ; Holds address entered by user
NumberOfBytes dw 1 ; Holds Number of Bytes to Display
ASCIIString db 48 dup (' '), ' ' ; Holds Mem converted to ASCII String
BeginString db ' ','*' ; Holds Start chars for End String
TextString db 17 dup (' ') ; Holds Valid Text Chars from mem
EndString db '*',0ah,0dh,'$' ; Holds End chars for End String
HoldSegment db 4 dup (' '),':','$'
HoldAddress db 4 dup (' '),' ','$'
.code ; Identifies code segment
main proc
mov ax,@data ; Load address of data into DS Register
mov ds,ax
; Get the segment and convert to 16-bit Integer
mov ah,09 ; Command String Output
mov dx,offset EnterSegment ; Get location of string
int 21h ; Output Segment Request
call Input ; Value returned in AX
mov SegmentToUse,ax ; Save returned value
mov ah,09 ; Command String Output
mov dx,offset ReturnString ; Get Location of Return String
int 21h ; Output Return String
; Get the address and convert to 16-bit Integer
mov ah,09 ; Command String Output
mov dx,offset EnterAddress ; Get location of string
int 21h ; Output Segment Request
call Input ; Value returned in AX
mov AddressToUse,ax ; Save returned value
mov ah,09 ; Command String Output
mov dx,offset ReturnString ; Get Location of Return String
int 21h ; Output Return String
; Get number of bytes and convert to 16-bit Integer
mov ah,09 ; Command String Output
mov dx,offset EnterNumByte ; Get location of string
int 21h ; Output Segment Request
call Input ; Value returned in AX
mov NumberOfBytes,ax ; Save returned value
mov ah,09 ; Command String Output
mov dx,offset ReturnString ; Get Location of Return String
int 21h ; Output Return String
; Output information to screen
mov es,SegmentToUse ; Load the Segment
mov si,AddressToUse ; Load the Address
OutputString:
mov di,offset ASCIIString; Load destination
mov al,' ' ; Load blank
mov ax,si ; Move Address to convert and print
mov al,ah
call ItoA
mov HoldAddress,ah
mov HoldAddress+1,al
mov ax,si
call ItoA ;176
mov HoldAddress+2,ah
mov HoldAddress+3,al
mov cx,48 ; load loop counter
ClearASCIIString: ; Removes all unnecessary characters
mov ds:[di],al ; Blank out the character
inc di ; Point to next location
loop ClearASCIIString
mov di,offset TextString ; Load destination
mov al,' ' ; Load blank
mov cx,16 ; load loop counter
ClearTextString: ; Removes all unnecessary characters
mov ds:[di],al ; Blank out the character
inc di ; Point to next location
loop ClearTextString
mov di,offset ASCIIString; Load destination
mov bp,offset TextString ; Load other destination
; Preparing to place the Ascii information
mov cx,NumberOfBytes
cmp NumberOfBytes,10h
jb Loop3
sub NumberOfBytes,10h
mov cx,10h
jmp Loop1
Loop3:
mov NumberOfBytes,0
Loop1 equ $ ; Checks for a printable character to place in text string
mov al,es:[si] ; Get a byte of memory
inc si ; Point to next byte
mov ds:[bp],' ' ; Place a blank in the text string
cmp al, ' ' ; Check Lower Bound
jb Loop2
cmp al, '}' ; Check Upper Bound
ja Loop2
mov ds:[bp],al ; Place the character in the text string
Loop2: ; Puts the ASCII codes in the main string.
inc bp ; Point to Next Location in the String
call ItoA ; AX will contain characters
mov ds:[di],ah ; Save the High Character
inc di ; Point to Next Location in String
mov ds:[di],al ; Save the Low Character
inc di ; Point to Next Location in String
mov ds:[di],' ' ; Load a blank character
inc di ; Point to Next Location in String
Loop Loop1
; Outputs the string to the screen
mov ax,es ; Move Segment to convert and print
mov al,ah
call ItoA
mov HoldSegment,ah
mov HoldSegment+1,al
mov ax,es
call ItoA
mov HoldSegment+2,ah
mov HoldSegment+3,al
mov ax,0900h
mov dx,offset HoldSegment
int 21h
mov ax,0900h
mov dx,offset HoldAddress
int 21h
mov ah,9 ; Command string output
mov dx,offset ASCIIString; Setup parameter
int 21h ; Command DOS Services
cmp NumberOfBytes,0 ; Continue until end of string
jnz OutputString
mov ax,4C00h ; Terminate Process
int 21h ; Invoke DOS Service
main endp ; End of the main procedure
; Beginning of Input procedure
Input proc
push bx ; Save registers that may be used
push cx
push dx
push si
; Input information from user
mov ah,1 ; Setup for retrieving a character
int 21h ; Call DOS Services
mov Here,al ; Save the 1st character
int 21h ; Call DOS Services
mov Here+1,al ; Save the 2nd character
int 21h ; Call DOS Services
mov Here+2,al ; Save the 3rd character
int 21h ; Call DOS Services
mov Here+3,al ; Save the 4th character
; Convert all the characters
mov bx,4 ; Load Loop Counter
mov si,offset Here ; Get Starting Address of string
xor dx,dx ; Clear dx register
mov cx,12 ; Load shift value
L1:
xor ax,ax ; Clear input register
mov al,[si] ; Get character from string
sub al,'0' ; Convert input to Number
cmp al,0ah ; Check for Alpha characters
jb cont1 ; Jump if numeric
sub al,7 ; Subtract off additional number
CONT1:
shl ax,cl ; Move data to correct position in number
add dx,ax ; Add quantity to Number
sub cl,4 ; Reduce shift count
inc si ; Point to next character
dec bx ; Reduce loop counter
jnz L1 ; Continue until done
; Put data in output register
mov ax,dx
; Restore the registers that were used
pop si
pop dx
pop cx
pop bx
ret
Input endp ; End of Input Procedure
; Beginning of ItoA Procedure
ItoA proc
; Save used registers
push bx
push cx
; Convert the upper nibble into Ascii
push ax ; Save for later
shr al,4 ; Obtain the upper nibble
and ax,0Fh ; Remove all unneeded bits
mov bx,ax ; Put into index register
mov ch,ASCIITable[bx] ; Convert to ASCII
; Convert the lower nibble into Ascii
pop ax ; Retrieve later
and ax,0Fh ; Remove all unneeded bits
mov bx,ax ; Put into index register
mov cl,ASCIITable[bx] ; Convert to ASCII
mov ax,cx ; Transfer to return value
; Restore the used registers
pop cx
pop bx
ret
ItoA endp
end main
title Memory Dump memorydump.asm
dosseg ; Specifies to use a DOS segment
.286 ; Enables pentium instructions
.model small ; Uses small memory model
.stack 100h ; Identifies Stack Segment at offset 100 Hex
.data
EnterSegment db 'Please Enter the 4 Digit Segment: ','$'
EnterAddress db 'Please Enter the 4 Digit Address: ','$'
EnterNumByte db 'Please Enter the Number of Bytes: ','$'
ReturnString db 0ah, 0dh, '$'
ASCIITable db '0123456789ABCDEF'
Here db 4 dup (' ')
SegmentToUse dw 1 ; Holds segment entered by user
AddressToUse dw 1 ; Holds address entered by user
NumberOfBytes dw 1 ; Holds Number of Bytes to Display
ASCIIString db 48 dup (' '), ' ' ; Holds Mem converted to ASCII String
BeginString db ' ','*' ; Holds Start chars for End String
TextString db 17 dup (' ') ; Holds Valid Text Chars from mem
EndString db '*',0ah,0dh,'$' ; Holds End chars for End String
HoldSegment db 4 dup (' '),':','$'
HoldAddress db 4 dup (' '),' ','$'
.code ; Identifies code segment
main proc
mov ax,@data ; Load address of data into DS Register
mov ds,ax
; Get the segment and convert to 16-bit Integer
mov ah,09 ; Command String Output
mov dx,offset EnterSegment ; Get location of string
int 21h ; Output Segment Request
call Input ; Value returned in AX
mov SegmentToUse,ax ; Save returned value
mov ah,09 ; Command String Output
mov dx,offset ReturnString ; Get Location of Return String
int 21h ; Output Return String
; Get the address and convert to 16-bit Integer
mov ah,09 ; Command String Output
mov dx,offset EnterAddress ; Get location of string
int 21h ; Output Segment Request
call Input ; Value returned in AX
mov AddressToUse,ax ; Save returned value
mov ah,09 ; Command String Output
mov dx,offset ReturnString ; Get Location of Return String
int 21h ; Output Return String
; Get number of bytes and convert to 16-bit Integer
mov ah,09 ; Command String Output
mov dx,offset EnterNumByte ; Get location of string
int 21h ; Output Segment Request
call Input ; Value returned in AX
mov NumberOfBytes,ax ; Save returned value
mov ah,09 ; Command String Output
mov dx,offset ReturnString ; Get Location of Return String
int 21h ; Output Return String
; Output information to screen
mov es,SegmentToUse ; Load the Segment
mov si,AddressToUse ; Load the Address
OutputString:
mov di,offset ASCIIString; Load destination
mov al,' ' ; Load blank
mov ax,si ; Move Address to convert and print
mov al,ah
call ItoA
mov HoldAddress,ah
mov HoldAddress+1,al
mov ax,si
call ItoA ;176
mov HoldAddress+2,ah
mov HoldAddress+3,al
mov cx,48 ; load loop counter
ClearASCIIString: ; Removes all unnecessary characters
mov ds:[di],al ; Blank out the character
inc di ; Point to next location
loop ClearASCIIString
mov di,offset TextString ; Load destination
mov al,' ' ; Load blank
mov cx,16 ; load loop counter
ClearTextString: ; Removes all unnecessary characters
mov ds:[di],al ; Blank out the character
inc di ; Point to next location
loop ClearTextString
mov di,offset ASCIIString; Load destination
mov bp,offset TextString ; Load other destination
; Preparing to place the Ascii information
mov cx,NumberOfBytes
cmp NumberOfBytes,10h
jb Loop3
sub NumberOfBytes,10h
mov cx,10h
jmp Loop1
Loop3:
mov NumberOfBytes,0
Loop1 equ $ ; Checks for a printable character to place in text string
mov al,es:[si] ; Get a byte of memory
inc si ; Point to next byte
mov ds:[bp],' ' ; Place a blank in the text string
cmp al, ' ' ; Check Lower Bound
jb Loop2
cmp al, '}' ; Check Upper Bound
ja Loop2
mov ds:[bp],al ; Place the character in the text string
Loop2: ; Puts the ASCII codes in the main string.
inc bp ; Point to Next Location in the String
call ItoA ; AX will contain characters
mov ds:[di],ah ; Save the High Character
inc di ; Point to Next Location in String
mov ds:[di],al ; Save the Low Character
inc di ; Point to Next Location in String
mov ds:[di],' ' ; Load a blank character
inc di ; Point to Next Location in String
Loop Loop1
; Outputs the string to the screen
mov ax,es ; Move Segment to convert and print
mov al,ah
call ItoA
mov HoldSegment,ah
mov HoldSegment+1,al
mov ax,es
call ItoA
mov HoldSegment+2,ah
mov HoldSegment+3,al
mov ax,0900h
mov dx,offset HoldSegment
int 21h
mov ax,0900h
mov dx,offset HoldAddress
int 21h
mov ah,9 ; Command string output
mov dx,offset ASCIIString; Setup parameter
int 21h ; Command DOS Services
cmp NumberOfBytes,0 ; Continue until end of string
jnz OutputString
mov ax,4C00h ; Terminate Process
int 21h ; Invoke DOS Service
main endp ; End of the main procedure
; Beginning of Input procedure
Input proc
push bx ; Save registers that may be used
push cx
push dx
push si
; Input information from user
mov ah,1 ; Setup for retrieving a character
int 21h ; Call DOS Services
mov Here,al ; Save the 1st character
int 21h ; Call DOS Services
mov Here+1,al ; Save the 2nd character
int 21h ; Call DOS Services
mov Here+2,al ; Save the 3rd character
int 21h ; Call DOS Services
mov Here+3,al ; Save the 4th character
; Convert all the characters
mov bx,4 ; Load Loop Counter
mov si,offset Here ; Get Starting Address of string
xor dx,dx ; Clear dx register
mov cx,12 ; Load shift value
L1:
xor ax,ax ; Clear input register
mov al,[si] ; Get character from string
sub al,'0' ; Convert input to Number
cmp al,0ah ; Check for Alpha characters
jb cont1 ; Jump if numeric
sub al,7 ; Subtract off additional number
CONT1:
shl ax,cl ; Move data to correct position in number
add dx,ax ; Add quantity to Number
sub cl,4 ; Reduce shift count
inc si ; Point to next character
dec bx ; Reduce loop counter
jnz L1 ; Continue until done
; Put data in output register
mov ax,dx
; Restore the registers that were used
pop si
pop dx
pop cx
pop bx
ret
Input endp ; End of Input Procedure
; Beginning of ItoA Procedure
ItoA proc
; Save used registers
push bx
push cx
; Convert the upper nibble into Ascii
push ax ; Save for later
shr al,4 ; Obtain the upper nibble
and ax,0Fh ; Remove all unneeded bits
mov bx,ax ; Put into index register
mov ch,ASCIITable[bx] ; Convert to ASCII
; Convert the lower nibble into Ascii
pop ax ; Retrieve later
and ax,0Fh ; Remove all unneeded bits
mov bx,ax ; Put into index register
mov cl,ASCIITable[bx] ; Convert to ASCII
mov ax,cx ; Transfer to return value
; Restore the used registers
pop cx
pop bx
ret
ItoA endp
end main
