https://stackoverflow.com/questions/17802071
italiano
english
français
española
中国
日本の
العربية
Deutsch
한국어
Português
RussianAs you mention trying interrupts, may we assume that your OS is 16-bit (at present)? You're interested in using int 10h functions? I also just came across some text about doing it by diddling ports (I can't tell you how to use that stuff... might work in pmode if your OS has gotten there). Using a graphics mode and "drawing" the characters is also interesting - text doesn't have to be on a straight line, it can "slope". I've got a ton of old dos programs that experiment with this. Unfortunately, I can't remember which does what, and I'm not in the mood to boot to dos and look for 'em. :(
Here's one I can lay my hands on from the legendary Beth Stone:
;From: "Beth"
; Balloon.asm
; (C)2K1 Beth (but donated to the public domain :)
;
; Simple .com file that demonstrates changing the
; video font for text mode 3 using the "official"
; BIOS interrupts for doing it...
;
; Note: mode 3 is a bit polymorphic in that the size
; of a character cell differs according to the video
; card...but, for modern VGAs and above, these will
; almost certainly have a 9x16 size character cell by
; default (but the older cards like CGA/EGA and such had
; a lower resolution and an 8x8 character cell)...that
; is, mode 3 is defined by the amount of character
; cells being 80x25 and the card alters the size of the
; character cell to make the resolution and this
; requirement correspond...
;
; As this is the case, I force the character cell to be
; 8x8 in this little program to make life easier in that
; I don't have to supply fonts for 8x8, 8x14, 8x16
; potential sizes...this, on a modern VGA and above,
; will force the number of rows on screen to 50 and
; produce shorter characters than usual...
;
; Finally, it's worth noting that the VGA(+) resolution
; of mode 3 is actually 720 pixels across rather than
; what you might assume of 640 (because we've 80
; columns each at 8 pixels wide and 80x8=640, which is
; not 720 :)...thus, these cards automatically insert
; a vertical gap of one pixel between the character
; cells (if you look at ASCII characters 176, 177,178
; and 219, you can see this in action...because
; although 219 is defined as "all pixels on" (a solid
; block) when you make a row of them, you'll see a gap
; between them...this you can see on my little balloon
; graphic also...
;
; Also, if you're going to run this from a DOS box in
; Windows, then you'll need to go into fullscreen mode
; because Windows _emulates_ text modes in a window
; and, thus, my little balloon won't show up (what's
; interesting, though, is that if you switch between
; fullscreen and a window with ALT + ENTER then you
; can see the difference...in fullscreen, you'll see
; the balloon but in a window, you'll just see weird
; extended ASCII characters)...
;
; Anyway, enough of these overly long comments (there's
; more comment here than actual program...hehehe ;)...
; let's get to some actual code...
;
; .model tiny
; .code
%define offset
section .text
org 100h
; Set the video mode to the standard text mode #3
;
Start: mov ax, 0003h
int 10h
; Load in the standard 8x8 ROM font...which also forces
; the video to use 8x8 character cells...
;
mov ax, 1112h
; int 10h
; Ok, let's load in my new font characters...
;
mov ax, 1110h
mov bx, 0800h
mov cx, 0007h
mov dx, 0080h
mov bp, offset NewFont
int 10h
; And let's print some characters to demonstrate my new
; font in action...
mov ax, 0900h
mov dx, offset Balloon
int 21h
; Goodbye program, hello DOS prompt!!!
; (i.e. call terminate program interrupt :)
;
mov ah, 4Ch
int 21h
Balloon db 0Ah, 0Dh, "Look! It's a balloon!", 0Ah, 0Dh
db "But, wait, we're in a text mode but that looks "
db "a lot like a graphic...", 0Ah, 0Dh,
db "how can this be?", 0Ah, 0Dh
db "Cool, huh? :)", 0Ah, 0Dh, 0Ah, 0Dh
db 128, 129, 130, 0Ah, 0Dh
db 131, 132, 133, 0Ah, 0Dh
db " ", 134, " ", 0Ah, 0Dh, 0Ah, 0Dh, "$"
; Here's the data for the new characters I'm
; defining...the format is a simple monochrome
; bitmap, where each bit in a byte represents a
; pixel (0 = off, 1 = on :) and there's 8 bytes
; to make up an 8x8 character...
;
; As I can't be bothered to calculate some interesting
; graphics of my own here, then I've loaned the already
; calculated values from the C64 user's guide for
; creating a balloon sprite (which, coincidentally,
; uses a similar format to the format I need here, so
; it saves time just to copy those values over rather
; than work out some of my own :)...just thought I'd
; explain why I've got a balloon with the Commodore
; logo on it as my graphic...the answer is simply that
; I was too lazy to sit with some graph paper and work
; out some values of my own...trust me, I've done it
; before on other occasions and it's a really long and
; tedious process :)...
;
NewFont db 0, 1, 3, 3, 7, 7, 7, 3
db 127, 255, 255, 231, 217, 223, 217, 231
db 0, 192, 224, 224, 240, 240, 240, 224
db 3, 3, 2, 1, 1, 0, 0, 0
db 255, 255, 255, 127, 62, 156, 156, 73
db 224, 224, 160, 64, 64, 128, 128, 0
db 73, 62, 62, 62, 28, 0, 0, 0
; end Start
Due to this being posted in Beht's Masm/Tasm syntax, and my quicky attempts to translate it to Nasm syntax, some of it looks a little weird. I notice I commented out Beth's int 10h at one point. Don't remember why. Give you something to play with anyway...
