[Computer Certification] Different brands of ink cartridges are available in the market. HP, Epson, Canon, Xerox, Compaq and Lexmark are a few well-known brands. Only cartridges and printers of the same brand are compatible with each other. Generally on an average 200 to 250 copies can be printed with one cartridge. This number varies with the use of different specifications with regard to color and quality. Using a printer with an empty cartridge can damage the print head of the printer. It is thus advisable to change the cartridge when the ink shows signs of exhaustion. [Tom]