screen processing
TRANSCRIPT
SCREEN PROCESSING
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THE MONITOR
A typical video screen has 80 columns numbered 0 to 79 and 25 rows numbered from 0 to 24
The columns and rows provide a grid of addressable locations at any one of which the cursor can be set
Example cursor locations:Screen location Column # Row # In Decimal Value
Column # Row # In Hexadecimal Value
Upper left corner 0 0 00h 00h
Upper right corner
79 0 4Fh 00h
Center of screen 40 12 28h 0Ch
Lower left corner 0 24 00h 18h
Lower right corner
79 24 4Fh 18h
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CLEARING THE SCREEN IN ASSEMBLY LANGUAGE
Interrupt 10h function 06h handles the process of clearing the screen and scrolling
MOV AH, 06HMOV BH, 07HMOV CX, 0000HMOV DX, 184FHINT 10H
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SETTING THE CURSOR POSITION
Interrupt 10h is the BIOS operation for screen handling and function 02h tells the operation to set the cursor
MOV AH, 02HMOV BH, 00HMOV DH, 0AHMOV DL, 08HINT 10H
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DISPLAYING THE CHARACTER ‘X’ AT THE CENTER OF THE SCREEN
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DISPLAYING A STRING AT THE CENTER OF THE SCREEN
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DISPLAYING ASCII CHARACTER SET
Character Single
Line
Hex Code Character Double
Line C4 CD B3 BA
BF BB
D9 BC
DA C9
C0 C8
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COLOR CHART
For colored monitors, the background can display one out of eight colors and text can display one out of 16 colors
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Color Hex Code
Intensity
Red Green blue
BLACK 0 0 0 0 0
BLUE 1 0 0 0 1
GREEN 2 0 0 1 0
CYAN 3 0 0 1 1
RED 4 0 1 0 0
MAGENTA 5 0 1 0 1
BROWN 6 0 1 1 0
WHITE 7 0 1 1 1
GRAY 8 1 0 0 0
LIGHT BLUE 9 1 0 0 1
LIGHT GREEN A 1 0 1 0
LIGHT CYAN B 1 0 1 1
LIGHT RED C 1 1 0 0
LIGHT MAGENTA
D 1 1 0 1
YELLOW E 1 1 1 0
HIGH INTENSITY WHITE
F 1 1 1 1
TEXT AND BACKGROUND COLOR
Example how to set the text and background colors and how to make them blink
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DISPLAYING CHARACTER ‘X’ WITH ATTRIBUTE
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DISPLAYING A STRING WITH ATTRIBUTES