Elementary Data Types

We have previously stated that all variables need be declared. This means that their names are introduced in the heading of the program. In addition to introducing the name (and thereby enabling a compiler to detect and indicate misspelled identifiers), declarations have the purpose of associating a data type with each variable. This data type represents information about the variable which is permanent in contrast, for example, to its value. This information may again aid in detecting inconsistencies in an erroneous program, inconsistencies that are detectable by mere inspection of the program text without requiring its interpretation.