Star Micronics SB-15 user manual

ask-key). There are ASCII codes for all the letters of the alphabet, both lower case and capital, the numbers from 0 to 9, most punctuation marks, and some (but not all) of SD-10/15’s func- tions.

ASCII codes are referred to in several different ways, depending on the way they are used. Some times these codes are treated as regular numbers. For example, the letter “A” is represented by the number 65 in ASCII. Appendix F shows all of the ASCII codes.

In BASIC, ASCII codes are used in the CHR$ function. This function is used to print the character that is represented by the number in the CHR$ function. The BASIC statement PRINT CHR$ (65) will print an “A” on the terminal.

In some other programming languages, ASCII codes are re- ferred to by their hex value. “Hex” is short for hexadecimal which is a base- 16 number system (our usual numbers are base- 10). Since hex needs 16 digits, it uses the numbers 0 through 9 and then it uses the letters A through F for digits. The ASCII code for the letter “A” is 41 in hex.

Of course, most of the time we don’t even need to think about this code system. Our computers are smart enough to know that when we press the “A” key on our keyboard we want to print the letter “A”. The computer takes care of all the rest.

But there are a number of ASCII codes that don’t have keys on the keyboard. The most important of these codes are the codes that have ASCII values below 32. These codes control many of SD-lo/l 5’s functions. Even though there aren’t keys for these codes, most keyboards can send these codes. It’s done by holding down the “control” key (many times marked CTRL) and si- multaneously pressing a letter key. The particular letter key that is pressed determines what code is sent. Control and A,sends ASCII code 1, control and B sends ASCII code 2, and so on. Because of the way they are created, these codes are often referred to as “control-A” etc.

So there are four common ways of referring to the same set of codes: the character or name of the code, the decimal ASCII value, the hexadecimal ASCII value, and the “control-” value.

For example, the code that causes SD-lo/l5 to advance the paper one line is ASCII 10 (decimal). This code is commonly referred to by all the following names: