User-defined Data Types

Pre-defined

(P,I,F,C,N,D,T,X)

Elementary

Structure type

Table type

Structured

User defined

Data type

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User-defined Data Types

User-defined data types can either be elementary or structured. User-defined elementary data types are based entirely on predefined elementary data types. To define your own elementary data types, you use the TYPES statement.

• User-defined elementary data types make your programs easier to read and maintain by giving them descriptive names that are easier to understand and more recognizable.
• Elementary data types cannot be included in further components. Structured data types, on the other hand, are made up freely of elementary and structured data types.
• In structured data types there is a difference between field string types and table types:
  • Field string types (known as structures or records in other terminology) can be made up of components of any type.
  • Table types (known as arrays in other terminology) can be made up of lines of any type
• Field string types and table types at the highest level can themselves contain further field string types and table types.