ASCII is an acronym for American Standard Code for Information Interchange. This is a character encoding system that uses a seven-bit code to represent characters through numbers. Because there are seven bits, there are 2 ⁷, or 128 characters (0 through 127). Although this system was created many years ago, it is still used today in numerous applications. In the area of production testing, the first eight ASCII characters are commands that can be found in some driver interface communications for handlers and wafer probers.

Table E.1 provides the mapping of characters per the ASCII standard along with the decimal and hexadecimal equivalents.