How does computer print characters

Today while reading an article on some website about localization a wierd thought just ran into my mind. Why does a computer print "A" when I press "A" key on my keyboard ? Well we all know that computers understand ASCII and when I press a key "A" on my keyboard a signal goes to CPU that user has pressed a key with ASCII code 65. This was the point beyond which I was not able to understand my problem. I mean it's all okey if computer understood that I pressed a keystroke with ASCII code 65 as computer is good at understanding binary. However I was still confused as to how did "A" got displayed on computer screen. And if we can change it to print some other character from some another language. However after a bit of searching on internet, I came to know that actually ROM BIOS of VGA card has something called "OEM Hardware Font". These fonts generally use U.S. English PC8 character set - Codepage 437. The fullscreen fonts are generally stored as bitmaps in BIOS data area and are copied to computer memory during the boot process. Several font sizes are provided. The most popular is 8x16 (8 pixels wide, 16 pixels high) but 8x8 and 8x14 fonts are also common. All video cards must provide 8x16 and 8x8 fonts. Some video cards drop 8x14 fonts as VESA standard encourages manufacturers to drop this font to allow for inclusion of some other features. So next question that was in mind was that can we change these fonts ?

Modern video cards hold their software and images in EEPROM. Though many manufacturers provide flash images to upgrade the software, very few of them provide proprietary ROM Images. However luckily for popular video cards there are many publically available editors which allows one to view these bitmaps and even modify them.Subscribe to Syconet World by Email.

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