A DOS 2.0 filter for word processing document files

call put_char ; send an ASCII blank
pop cx
loop clean55
jmp clean3

clean6: call put_char ; write out the EOF mark,
ret ; and return to DOS.

clean endp


get_char proc near
mov bx,stdin ; get chars from std. input
mov cx,1 ; # of chars to get = 1
mov dx,offset input_buffer ; location = input_buffer
mov ah,3fh
int 21h ; do the function call
or ax,ax ; test # of chars returned
jz get_char1 ; if none, return EOF
mov al,input_buffer ; else, return the char in AL
ret
get_char1:
mov al,eof ; no chars read, return
ret ; an End-of-File (EOF) mark.
get_char endp

put_char proc near
mov output_buffer,al ; put char to write in buffer.
mov bx,stdout ; write to std. output
mov cx,1 ; # of chars = 1
mov dx,offset output_buffer ; location = output_buffer
mov ah,40h
int 21h ; do the function call
cmp ax,1 ; check to see it was really done.
jne put_char1
clc ; really done. return carry = 0
ret ; as success signal.
put_char1:
stc ; not really done. return carry = 1
ret ; as error signal (device is full).
put_char endp

input_buffer db 0
output_buffer db 0

column dw 0

err_msg db cr,lf
db 'clean: Disk is full.'
db cr,lf
err_msg_len equ (this byte)-(offset err_msg)

cseg ends

end clean