Star Micronics NX-10 user manual OPEN4,4 CMD4 List

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output to the screen.

Other computers, notably the Commodore C-64, require you to open the printer as a numbered device then to direct output to that device. For example, you might type the following to print “Hello!” or to list a program in the C-64’s memory.

OPEN4,4	OPEN4,4
CMD4	CMD4
LIST	PRINT "Hello! 'I
CLOSE 4	CLOSE4

Here, the first line says that the printer is device number 4, the second directs output to it, the third does the printing, and the last line closes down device number 4.

Appendix H gives more information about listing programs on the various computers. Find the part that applies to your com- puter and try it.

Now that we know how to address the printer, let’s try listing a BASIC program. Load a program into memory ready to pro- gram printer operation - just as soon as we learn a little bit about the ASCII codes.

W ASCII codes and the CHR$ function

You talk to your computer in BASIC, but your computer and your printer talk to each other in what are known as ASCII codes. In the ASCII code, each number from 0 to 255 has a par- ticular meaning - 36, for example, makes the printer print a dollar sign. Some numbers cause the printer to do other things, too. For instance, sending a 7 sounds the printer’s bell.

Taken together, these numbers and their meanings make up the ASCII code (pronounced ask-key), which stands for the American Standard Code for Information Interchange. There are ASCII codes for all the letters of the alphabet (upper case and lower case), 0 to 9, most punctuation marks, and some (but not all) of the functions of the printer.

There are a number of different ways to represent an ASCII code, depending on how you are using it. For example, the ASCII codes for the letter “A” are 65 (decimal) or &H41 (hex- adecimal). Or you can just call it “A”. Appendix B shows all of the ASCII codes.

BASIC uses the CHR$ function to represent ASCII characters and many functions. To print the letter “A” we