Notes:The Adventures of Captain Comic (DOS)

This page contains notes for the game The Adventures of Captain Comic (DOS).

Revisions

The Internet Archive has all five revisions under the item TheAdventuresOfCaptainComic:

• sw1988
• R2sw1988
• R3sw1989
• R4sw1989
• R5sw1991

It also has three other versions:

• swh11988 (file_id.diz labels it "Hacked/grafitti version 1")
• swh21988 (file_id.diz labels it "Hacked/grafitti version 2")
• R4a1sw1989 (file_id.diz labels it "Alternate version 1")

File Formats

Malvineous has documented the file formats here.

Executable Packing

In every revision, COMIC.EXE is packed with EXEPACK. Revision 1 uses an earlier version of EXEPACK that not all unpackers can handle. Try these ones:

• https://www.bamsoftware.com/software/exepack/
• https://github.com/w4kfu/unEXEPACK

R1swh21988 (a hacked version) doesn't have COMIC.EXE but rather MENU.EXE, and the EXEPACK layer appears to be wrapped in another layer that adds an advertisement for "Red Point".

Sound Effects

The format of a sound effect is an array of

struct {
    uint16_t freq_divider;
    uint16_t duration;
};

The 16-bit values are stored little-endian. Each freq_divider divides the Programmable Interval Timer base frequency of 1193182 Hz. For example, a freq_divider of 1c3f would result in an output frequency of 1193182 / 0x1c3f ≈ 165 Hz. The special freq_divider value 0028 indicates a rest. duration is in number of beats; each beat is about 55 ms (one tick of the 18.2 Hz IRQ 0 timer). The end of the sound is marked by a freq_divider of 0000.

Table of offsets to sound effects in the unpacked executable. Assumes that the unpacked executable has an EXE header of 512 bytes. Changed sounds are highlighted.

	R1sw1988	R1swh11988	R2sw1988	R3sw1989	R4a1sw1989	R4sw1989	R5sw1991
title	2521	2521	25a2	25d2	27a2	27a2	29c4
start	2665	2665	2bc0	2bf2	2daa	2d9e
door	eda9	eda9	f309	f339	f4f9	f4e9	fc29
player death	edd1	edd1	f331	f361	f521	f511	fc51
teleport	edf9	edf9	f359	f389	f549	f539	fc79
bonus	ee19	ee19	f379	f3a9	f569	f559	fc99
materialize	ee25	ee25	f385	f3b5	f575	f565	fca5
game over	ee85	ee85	f3e5	f415	f5d5	f5c5	fd05
screen transition	eede	eede	f43e	f46f	f62f	f61f	fd3f
lost life	eefe	eefe	f45e	f48f	f64f	f63f	fd5f
shoot	ef4e	ef4e	f4ae	f4de	f69e	f68e	fdae
enemy death	ef5a	ef5a	f4ba	f4ea	f6aa	f69a	fdba
player damaged	ef71	ef71	f4d1	f501	f6c1	f6b1	fdd1
item get	ef81	ef81	f4e1	f511	f6d1	f6c1	fde1
extra life	ef95	ef95	f4f5	f525	f6e5	f6d5	fdf5

References for Code Changes

R3 Esc

Revision 2 @ 76	Revision 3 @ 76
cd16 int 0x16 ; get keystroke; al=ASCII code 3c6b cmp al, 0x6b ; 'k' 7407 je setup_keyboard 3c4b cmp al, 0x4b ; 'K' 7403 je setup_keyboard e95001 jmp game_start setup_keyboard:	cd16 int 0x16 ; get keystroke; al=ASCII code 3c6b cmp al, 0x6b ; 'k' 740e je setup_keyboard 3c4b cmp al, 0x4b ; 'K' 740a je setup_keyboard 3c1b cmp al, 0x1b ; Esc 7503 jne any_other_key e95203 jmp terminate_program any_other_key: e95401 jmp game_start setup_keyboard:

R3 Keyboard Setup Hack

Revision 2 @ 83	Revision 3 @ 8a
setup_keyboard: 1e push ds b8b70f mov ax, 0xfb7 ; segment containing keyboard-related strings 8ed8 mov ds, ax ; set ds to it e8f200 call input_key_mapping ; eat the 'k' already released b80200 mov ax, 2 ; video mode 2 (80x25 text) cd10 int 0x10 ; set video mode (clear screen)	setup_keyboard: 1e push ds b8b70f mov ax, 0xfb7 ; segment containing keyboard-related strings 8ed8 mov ds, ax ; set ds to it b80200 mov ax, 2 ; video mode 2 (80x25 text) cd10 int 0x10 ; set video mode (clear screen)

R3 Keyboard Buffer

Interrupts were disabled in two places:

Revision 2 @ 115	Revision 3 @ 1d1
; 0040:1a is pointer to beginning of the buffer of pending keystrokes ; 0040:1c is pointer to end 268a0e1a04 mov cl, byte es:[0x41a] 26880e1c04 mov byte es:[0x41c], cl ; set end = beginning	; 0040:1a is pointer to beginning of the buffer of pending keystrokes ; 0040:1c is pointer to end fa cli ; disable interrupts 268a0e1a04 mov cl, byte es:[0x41a] 26880e1c04 mov byte es:[0x41c], cl ; set end = beginning fb sti ; enable interrupts

Revision 2 @ 2b4	Revision 3 @ 2bf
; 0040:1a is pointer to beginning of the buffer of pending keystrokes ; 0040:1c is pointer to end 268a0e1a04 mov cl, byte es:[0x41a] 26880e1c04 mov byte es:[0x41c], cl ; set end = beginning	; 0040:1a is pointer to beginning of the buffer of pending keystrokes ; 0040:1c is pointer to end fa cli ; disable interrupts 268a0e1a04 mov cl, byte es:[0x41a] 26880e1c04 mov byte es:[0x41c], cl ; set end = beginning fb sti ; enable interrupts

Interrupts were not disabled at four other instances of the same pattern:

Revision 2 @ ff5	Revision 3 @ 1004
268a0e1a04 mov cl, byte es:[0x41a] 26880e1c04 mov byte es:[0x41c], cl	268a0e1a04 mov cl, byte es:[0x41a] 26880e1c04 mov byte es:[0x41c], cl

Revision 2 @ 103f	Revision 3 @ 104e
268a0e1a04 mov cl, byte es:[0x41a] 26880e1c04 mov byte es:[0x41c], cl	268a0e1a04 mov cl, byte es:[0x41a] 26880e1c04 mov byte es:[0x41c], cl

Revision 2 @ 110b	Revision 3 @ 111a
268a0e1a04 mov cl, byte es:[0x41a] 26880e1c04 mov byte es:[0x41c], cl	268a0e1a04 mov cl, byte es:[0x41a] 26880e1c04 mov byte es:[0x41c], cl

Revision 2 @ 1228	Revision 3 @ 1237
268a0e1a04 mov cl, byte es:[0x41a] 26880e1c04 mov byte es:[0x41c], cl	268a0e1a04 mov cl, byte es:[0x41a] 26880e1c04 mov byte es:[0x41c], cl

R3 Key Mapping

Revision 2 @ 17e

Revision 3 @ 174

input_key_mapping: 2ec6061f0000 mov byte cs:[last_key], 0 ; set in int9_handler 2e803e1f0000 cmp byte cs:[last_key], 0 74f8 je input_key_mapping ; loop until a key is released 2e8a1e1f00 mov bl, byte cs:[last_key] 32ff xor bh, bh ; bx = scancode 2e3a1e1900 cmp bl, byte cs:[scancode_jump] 74e4 je input_key_mapping 2e3a1e1b00 cmp bl, byte cs:[scancode_left] 74dd je input_key_mapping 2e3a1e1c00 cmp bl, byte cs:[scancode_right] 74d6 je input_key_mapping 2e3a1e1a00 cmp bl, byte cs:[scancode_fire] 74cf je input_key_mapping 2e3a1e1d00 cmp bl, byte cs:[scancode_open] 74c8 je input_key_mapping 4b dec bx ; scancode == 0x1 (Esc)? 74c5 je input_key_mapping 83fb51 cmp bx, 0x51 ; scancode > 0x52 (Ins)? 7fc0 jg input_key_mapping d1e3 shl bx, 1 d1e3 shl bx, 1 d1e3 shl bx, 1 8d164a40 lea dx, word [key_names] 03d3 add dx, bx ; look up the key's name b409 mov ah, 9 cd21 int 0x21 ; print string 2ea01f00 mov al, byte cs:[last_key] ; return scancode c3 ret

input_key_mapping: e84400 call wait_for_keypress 8ad8 mov bl, al 32ff xor bh, bh ; bx = scancode 8bf3 mov si, bx 2e3a1e1900 cmp bl, byte cs:[scancode_jump] 74f0 je input_key_mapping 2e3a1e1b00 cmp bl, byte cs:[scancode_left] 74e9 je input_key_mapping 2e3a1e1c00 cmp bl, byte cs:[scancode_right] 74e2 je input_key_mapping 2e3a1e1a00 cmp bl, byte cs:[scancode_fire] 74db je input_key_mapping 2e3a1e1d00 cmp bl, byte cs:[scancode_open] 74d4 je input_key_mapping 4b dec bx ; scancode == 0x1 (Esc)? 74d1 je input_key_mapping 83fb52 cmp bx, 0x52 ; scancode > 0x53 (Del)? 7fcc jg input_key_mapping d1e3 shl bx, 1 d1e3 shl bx, 1 d1e3 shl bx, 1 8d164a40 lea dx, word [key_names] 03d3 add dx, bx ; look up the key's name b409 mov ah, 9 cd21 int 0x21 ; print string 8bc6 mov ax, si ; return scancode c3 ret wait_for_keypress: 2ec6061f0000 mov byte cs:[last_key], 0 ; set in int9_handler 2e803e1f0000 cmp byte cs:[last_key], 0 74f8 je wait_for_keypress ; loop until a key is pressed ; clear BIOS keyboard buffer 33c0 xor ax, ax 8ec0 mov es, ax 2ea01f00 mov al, byte cs:[last_key] ; return scancode fa cli 268a0e1a04 mov cl, byte es:[0x41a] 26880e1c04 mov byte es:[0x41c], cl fb sti c3 ret

R3 Key Press/Release

Revision 2 @ 3f8

Revision 3 @ 405

saved_int9_handler: ; pointer to the original handler for interrupt 9 00000000 dw 0x0000, 0x0000 int9_handler: ; IRQ 1, keyboard data ready, called for every keyboard event 50 push ax 53 push bx 51 push cx 52 push dx e460 in al, 0x60 ; al = scancode 50 push ax ; save al 9c pushf 2eff1ef803 lcall cs:[saved_int9_handler] ; call original interrupt handler 58 pop ax ; restore al = scancode ba0100 mov dx, 1 ; initially set dl = 1 to indicate key press a880 test al, 0x80 ; check the high bit of the scancode 7408 jz continue ; if 0, it was indeed a key press 247f and al, 0x7f ; otherwise, it was a key release 2ea21f00 mov byte cs:[last_key], al ; clear high bit and store scancode 33d2 xor dx, dx ; set dl = 0 to indicate key release continue:

saved_int9_handler: ; pointer to the original handler for interrupt 9 00000000 dw 0x0000, 0x0000 int9_handler: ; IRQ 1, keyboard data ready, called for every keyboard event 50 push ax 53 push bx 51 push cx 52 push dx e460 in al, 0x60 ; al = scancode 50 push ax ; save al 9c pushf 2eff1e0504 lcall cs:[saved_int9_handler] ; call original interrupt handler 58 pop ax ; restore al = scancode ba0100 mov dx, 1 ; initially set dl = 1 to indicate key press a880 test al, 0x80 ; check the high bit of the scancode 7406 jz key_was_pressed ; if 0, it was indeed a key press 247f and al, 0x7f ; otherwise, it was a key release 33d2 xor dx, dx ; set dl = 0 to indicate key release eb04 jmp continue ; do not store scancode key_was_pressed: 2ea21f00 mov byte cs:[last_key], al ; clear high bit and store scancode continue: