The following rules apply to user-assigned symbols, i.e. the names of variables, functions, operators, classes and labels in APLX.
The first character of the name must be one of the alphabetic characters A-Z or a-z, or one of the characters ‘ or þ. Subsequent characters can also include digits 0-9, underbar _ and high minus ¯.
Names consist of up to 30 characters (longer names will be truncated).
The following are all valid names in APLX:
DATA X X1 FIRST_VALUE ‘ ‘L1 ErrorCode model mode¯restart a999 Item‘1
Case is significant in names, so DATA Data and data are three distinct names.
There are no reserved names in APL. System-assigned names are distinct from user-assigned names because they start with a Quad Œ symbol.