;FILENAME:	UNIT14.TXT
;
; ASSEMBLY LANGUAGE COURSE, UNIT 14
; By Don Stoner Revision: 2008.07.20
;
; This program allows you to experiment
; with different text and graphical
; display formats.
;
	ORG 100h  ; Code Starts at 100h
	;
	; Instead of a normal LOOP_BACK
	; here we will do a little
	; trick with a CALL that will
	; enable us to loop back with
	; a single byte RET instruction
	;
LOOP_BACK:	; Loop back to here
	CALL RUN_LOOP
	JMP LOOP_BACK	;from here
RUN_LOOP:
	; Everything from here on down
	; is one big subroutine:
	;------------------------------
	; Output some text:
	;
	CALL INLINE_ASCIIZ_OUT
	DB "CHARACTER TEST",0
	;
	; Set the Point at Screen
	; Position 100,100 to Blue
	;
	MOV CX,100   ; X coordinate
		     ; (0 is left edge)
	MOV DX,100   ; Y coordinate
		     ; (0 is top)
	MOV AL,13    ; Color = Magenta
	; (Different screen modes use
	; different color numbering.)
	;
	MOV AH,0CH ;Code to set 1 point
	XOR BH,BH    ;(use page 0)
	INT 10h	     ;Video interrupt
	;
	; Fetch a key to tell the
	; program what to do next:
	;
	CALL ASCII_IN	;Read key to AL
	;
	; Select display depending
	; on which key was pressed:
	;------------------------------
	; VGA modes: (AH=0, AL=mode)
	; AL=03h:  80x25 16-color text
	; AL=42h: 132x43 16-color text
	; AL=44h: 132x60 16-color text
	;
	; "1" selects VGA mode 3
	; (80x25 16-color text)
	;
	CMP AL,"1"
	JNZ NT1
	MOV AX,3     ;VGA mode 3
	INT 10h	     ;Video interrupt
	RET	;Return to LOOP_BACK
NT1:	;
	; "2" selects VGA mode 42
	; (132x43 16-color text)
	;
	CMP AL,"2"
	JNZ NT2
	MOV AX,42    ;VGA mode 42
	INT 10h	     ;Video interrupt
	RET	;Return to LOOP_BACK
NT2:	;------------------------------
	; VESA graphic modes:(AX=4F02h)
	;  Table of BX (in hex) 
	; colors:   16 256 32K 64K 16M
	; 320x 200  0D  13 10D 10E 10F
	; 640x 480  11 101 110 111 112
	; 800x 600 102 103 113 114 115
	;1024x 768 104 105 116 117 118
	;1280x1024 106 107 119 11A 11B
	;
	; "3" selects VESA mode 0Dh
	; 320x200 16-color graphics
	;
	CMP AL,"3"
	JNZ NT3
	MOV BX,0Dh	;320x200,16
	MOV AX,4F02h	;VESA mode
	INT 10h	     ;Video interrupt
	RET	;Return to LOOP_BACK
NT3:	;
	; "4" selects VESA mode 105
	; 1024x768 256-color graphics
	;
	CMP AL,"4"
	JNZ NT4
	MOV BX,105h	;1024x768,265
	MOV AX,4F02h	;VESA mode
	INT 10h	     ;Video interrupt
	RET	;Return to LOOP_BACK
NT4:	;
	; "5" selects VESA mode 107
	; 1280x1024 256-color graphics
	;
	CMP AL,"5"
	JNZ NT5
	MOV BX,107h	;1280x1024,265
	MOV AX,4F02h	;VESA mode
	INT 10h	     ;Video interrupt
	RET	;Return to LOOP_BACK
NT5:	;------------------------------
	; Escape?	(1Bh)
	;
	CMP AL,1Bh	;(Escape key)
	JNZ NTESC
	MOV AX,3     ;Restore normal
	INT 10h	     ;VGA mode 3
	INT 20h	     ;And return to DOS
NTESC:	;
	RET
;--------------------------------------
%INCLUDE "UNIT11.ASM"	;(Subroutines)