Introduction

A data type is a piece of software information which specifies for a data item:

  • its structure

  • its format

  • a list of its attributes

  • its behavior

These properties are shared by all instances of the data type.

Illustration

The data type families are filed in different categories (dark gray).

Definitions

Data type families and their definitions.

Family

Definition

EDT

Elementary data types, such as:

  • Bool

  • Int

  • Byte

  • Word

  • Dword

  • etc.

DDT

Derived Data Types, such as:

  • Arrays, which contain elements of the same type:

    • Bool tables (EDT tables)

    • EBool tables (Device DDT Arrays)

    • tables of tables (DDT tables)

    • tables of structures (DDT tables)

  • structures, which contain elements of the different types:

    • Bool structures, Word structures, etc. (EDT structures)

    • EBool tables (Device DDT structure)

    • structures of tables, structures of structures, structures of tables/structures (DDT structures)

    • Bool structures, table structures, etc. (EDT and DDT structures)

    • structures concerning input/output data (IODDT structures)

Device DDT

Device Derived Data Types, such as:

  • tables, which contain elements of the same type:

    • Bool tables (EDT tables)

    • tables of tables (DDT tables)

    • tables of structures (DDT tables)

  • structures, which contain elements of the different types:

    • Bool structures, Word structures, etc. (EDT structures)

    • structures of tables, structures of structures, structures of tables/structures (DDT structures)

    • Bool structures, table structures, etc. (EDT and DDT structures)

    • structures concerning input/output data

    • Structures containing variables that restore the status properties of an action or transition of a Sequential Function Chart

EFB

Elementary Function Blocks written in C language. These comprise:

  • input variables

  • internal variables

  • output variables

  • a processing algorithm

DFB

Derived Function Blocks written in automation languages (Structured Text, Instruction List, etc.). These comprise:

  • input variables

  • internal variables

  • output variables

  • a processing algorithm