Category : Utilities for DOS and Windows Machines
Archive   : EBREAK.ZIP
Filename : EBREAK.ASM

Output of file : EBREAK.ASM contained in archive : EBREAK.ZIP
; EBREAK v1.0 - enhanced break - Public Domain by TLG Software
; EBREAK is a resident program that makes the Cntl-Break key "stronger",
; so that it will even break out of tight loops which don't involve DOS
; calls.
; NOTE: When Cntl-Break is hit the hardware interrupts (below 20H) are
; all reset to their values as of when the program was installed.
; Therefore, if you are installing resident programs which steal
; these interrupts they should be installed BEFORE this program.
; This program steals int 09H and int 1BH.
; Cntl-Break resets the system timer to run at the normal rate,
; and restores the video mode to the state it was in when EBREAK
; was installed.
; Copyright (c) 1986 by TLG software
; (O Cheyette, DB Clegg, M Golden)
; This program is hereby placed into the public domain.
; EBREAK is, however, copyrighted by the authors. You may make
; copies of EBREAK for your own use, and you may make copies for
; others.
; TLG software does not warrant that EBREAK operates as designed,
; and is not liable for any damages of any kind sustained through
; the use of the program.

code segment para public
assume cs:code

steal_int macro int_num,subst_int,old_int
mov bx,int_num * 4
mov ax,word ptr es:[bx]
mov word ptr old_int, ax
mov ax,word ptr es:[bx+2]
mov word ptr old_int[2], ax
mov word ptr es:[bx], offset subst_int
mov word ptr es:[bx+2], cs

IntVecs segment at 0
org 9 * 4
int_9 dd ?
org 1Bh * 4
int_1B dd ?
org 449H
video_state db ?
IntVecs ends

org 2Ch
environment label word


org 5CH
DOS_1B dd ? ; DOS int 1B
real_int_9 dd ? ; keyboard handler
called_cs dw ?
break_flag db ?
int_mask db ? ; original interrupts enabled
orig_int_tbl db 80H dup(?) ; room for copy of int tbl
; Note that table is on a double word
initial_mode db ? ; initial video mode

org 100h
start: jmp setup

assume ds:nothing, es:nothing

handle_9 proc far ; grabs the code segment of
push bp ; code executing when key was hit
mov bp,sp
mov bp,[bp+4] ; code segment of caller
mov called_cs,bp
pop bp
mov break_flag,0 ; clear break
pushf ; fake an interrupt
call real_int_9
test break_flag,BREAK_HIT ; did we get break?
jz no_break

in al,61H ; turn off sound
jmp short $+2
and al,0FCH
out 61H,al

mov al,36H ; reset system timer
out 43H,al
xor al,al
jmp short $+2
out 40H,al
jmp short $+2
out 40H,al

mov cx,40H ; restore int tbl
push cs
pop ds
assume ds:code
xor ax,ax
mov es,ax
assume es:IntVecs
mov di,ax
mov si,offset orig_int_tbl
rep movsw

mov al,int_mask ; restore enabled ints
out 21H,al

mov al,initial_mode ; set video back to original
cmp video_state,al
je vid_ok
xor ah,ah
int 10H

mov ax,4C01h ; can we really do this?!!?
int 21H ; YOW!

iret ; done
handle_9 endp

handle_1B proc far
assume ds:nothing, es:nothing
push ax
mov ax,cs
cmp called_cs,ax
jbe called_from_below ; check if were in DOS
cmp called_cs,0A000H
jae called_from_below ; or in BIOS
or break_flag,BREAK_HIT
pop ax
jmp DOS_1B ; do DOS's int 1B
handle_1B endp

handler_end label byte

HANDLE_1B_LEN equ $ - handle_1B

installing_msg db 'EBREAK v1.0 installed. ',
Copyright db 'Copyright (c) 1986, TLG Software - Public Domain',
db 0Dh, 0Ah
installing_msg_len equ $ - installing_msg
not_inst_msg db 'EBREAK previously installed.', 0Dh, 0Ah
not_inst_msg_len equ $ - not_inst_msg

assume ds:code, es:nothing
steal proc far
mov es,environment ; free environment area
mov ax,4900H
int 21H

xor ax,ax ; set up es to IntVecs
mov es,ax
assume es:IntVecs

les di,int_1B ; check for already installed
assume es:nothing
mov cx,HANDLE_1B_LEN
mov si,di
repz cmpsb
jcxz already_installed

mov es,ax ; point es to IntVecs again
assume es:IntVecs

steal_int 09H,handle_9,real_int_9
steal_int 1BH,handle_1B,DOS_1B

mov cx,40H ; save int tbl
push cs
pop es
assume es:code
xor ax,ax
mov ds,ax
assume ds:IntVecs
mov si,ax
mov di,offset orig_int_tbl
rep movsw

in al,21H ; save enabled ints
mov int_mask,al

mov al,video_state ; save video mode
mov initial_mode,al

push cs
pop ds ; restore segment
assume ds:code
mov dx,offset installing_msg
mov cx,installing_msg_len
mov bx,1
mov ax,4000h
int 21h
mov dx,offset handler_end
int 27H ; terminate and stay resident

mov dx,offset not_inst_msg
mov cx,not_inst_msg_len
mov bx,1
mov ax,4000h
int 21h
int 20h ; exit, not installing code
steal endp

code ends
end start

  3 Responses to “Category : Utilities for DOS and Windows Machines
Archive   : EBREAK.ZIP
Filename : EBREAK.ASM

  1. Very nice! Thank you for this wonderful archive. I wonder why I found it only now. Long live the BBS file archives!

  2. This is so awesome! 😀 I’d be cool if you could download an entire archive of this at once, though.

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