those of declarations, would have been incompatible with those allowing a natural and convenient representation of the additional features of Pascal. 

The main extensions relative to Algol 60 lie in the domain of data-structuring facilities, since their lack in Algol 60 was considered as the prime cause for its relatively narrow range of applicability. The introduction of record and file structures should make it possible to solve commercial-type problems with Pascal, or at least to employ it successfully to demonstrate such problems in a programming course. 

## 2. Summary of the Language 

A computer program consists of two essential parts, a description of actions which are to be performed, and a description of the data that are manipulated by these actions. Actions are described by so-called statements, and data are described by so-called declarations and definitions. 

The data are represented by values of variables. Every variable occurring in a statement must be introduced by a variable decim'ation, which associates an identifier and a data type with that variable. The type essentially defines the set of values that may be assumed by that variable, and restricts the set of valid operations on those values. A type in Pascal may be either directly described in the variable declaration, or it may be associated with a type identifier by a type definition and then represented by name. 

The simple types are the predefined type Real and the various ordinal types. Every simple type defines an ordered set of values. Each ordinal type is characterized by a one-to-one mapping from its values to an interval of the integers - the so-called ordinal numbers of those values. 

The basic ordinal types are the programmer-defined enumerated types and the predefined types Boolean, Char, and Integer. An enumerated type introduces a new set of values and a distinct identifier to denote each value. The values of Char are denoted by quotations, and the values of Integer and Real are denoted by numbers; these are syntactically distinct from identifiers. The set of values of type Char 

