AMT Datasouth PAL - Manual (Page 41)

35
_barcode: Code 128
string beginning with a tilde (~). To get the character tilde, two tildes (~~) are used. These charac-
ters are shown in the following table.
Three characters, \ ( and ), require special handling in PAL. The backslash character, \, is an es-
cape character for encoding special characters in PAL strings. To get the backslash character itself,
you must use a double backslash (\\). The parenthesis characters are used in PAL to indicate the
beginning and ending of a string. To include these characters in a string, they must be proceeded
by a backslash (i.e., \( and \) ).
Code C values are specified as a string of ASCII numerals. Since the Code 128 symbols are made
up of pairs of numerals, there must be an even number of numerals in the string. If PAL encounters
a non-numeral while building a Code C bar code, the string will be rejected with a rangecheck
error.
For Code A and Code B, the character used for a Code 128 symbol is usually the matching ASCII
character. Since there could be a problem getting some of the ASCII control characters in Code A
through some communication systems (not to mention PAL itself), these Code A characters are
requested by using the equivalent character from Code B (e.g. for ACK, use (f)). See the table be-
low for a complete list of all the PAL strings needed to produce Code 128 symbols. Any inap-
propriate ASCII character in the data string will cause the string to be rejected with a rangecheck
error.
A Code 128 bar code must start with a start code indicating the code to be used. If the data string
does not begin with one of the three start codes (~a, ~b, or ~c), a start code for Code B is supplied
by PAL. Code 128 allows the code to be changed within the bar code. If the code is changed, PAL
automatically begins using the rules for the new code.