Epson LQ-2550 User Manual - Page 110

When buying graphics software, always make sure the program has an option to print on an LQ printer. Any program with an option for an LQ printer should give excellent results, using different dot densities to produce a realistic scale of grays. If you plan to use color, be sure that the program supports color for an LQ printer. Most graphics programs have a printer selection procedure, in which case you should check the lists on page 4-2 to find the proper selection. Computer-Printer Communication Your computer communicates with your printer using a standardized set of numbered codes called ASCII codes (American Standard Code for Information Interchange). When you press the letter A on the keyboard, it is translated into the ASCII code for A, transmitted to a peripheral device such as your computer screen or your printer, and then converted back into the letter A. There are ASCII codes for all the letters in the alphabet, both uppercase and lowercase letters, and for the numbers 0 through 9. The ASCII set of codes also includes most punctuation marks and some codes that control printer functions. In the Command Summary in Chapter 8, each code is expressed three different ways: as an ASCII character, as a decimal number, and as a hexadecimal (base 16) number. For example, the uppercase letter A is represented as the ASCII character A, the decimal number 65, and the hexadecimal number 41. The numbering system you use depends on your software and your preferences. All letters, numbers, and punctuation marks are assigned decimal numbers from 32 through 255. ASCII codes with decimal values of less than 32 are called control codes, because they control the operation of your printer and other peripherals. These ASCII characters do not usually have corresponding keys on the keyboard and cannot be printed as characters by your printer. Using Software and Graphics 4-5