Table 3 shows the base data types that are supported in ZPL. All of the base types except boolean, file and string are considered to be arithmetic types. The arithmetic types all have C equivalents, which is important when invoking external C procedures (see Section 8.2). The integral types consist of all arithmetic types except for float and double.
Variables of type boolean have one of two values: true or false, which represent logical true and logical false, respectively.
The file data type is used to specify file I/O (Section 7.4
describes file I/O). Variables of type file can be assigned to,
passed to procedures as parameters, and returned from procedures; they
cannot be used as operands to any of the operators listed in
Table 5 (see page 
).
The string data type represents a sequence of characters. Variables of this type may be assigned to, initialized as config parameters (Section 4.1.1 describes config parameters), and passed to and returned from procedures.
Table 3: Base Types in ZPL (and their C equivalents).