Introduction

A data item designates an object which can beinstantiated such as:

• a variable,

• a function block.

Data is defined in three phases. These are:

• the data types phase, which specifies the following:

  • its category,

  • its format.

• the data instances phase, which defines its storage location and property, which is:

  • located, or

  • unlocated.

• the data references phase, which defines its means of access:

  • by immediate value,

  • by name,

  • by address.

Illustration

The following are the three phases that characterize the data:

Instantiating a data item consists in allocating it a memory slot according to its type.

Referencing a data item consists in defining a reference for it (name, address, etc.) allowing it to be accessed in the memory.