Chapter 3. Data Types and Fields

The design of an application should begin at the simplest level, with the design of the data elements. The type of data your development tool supports has a significant effect on our design. Since NAV is designed for financially oriented business applications, NAV data types are financial and business oriented.

In this chapter, we will cover many of the data types that we use within NAV. For each data type, we will cover some of the more frequently modified field properties and how particular properties, such as FieldClass, are used to support application functionality. FieldClass is a fundamental property that defines whether the contents of the field are data to be processed or control information to be interpreted. In particular, we will cover the following topics:

• Basic definitions
• Fields
• Data types
• FieldClass properties
• Filtering

Basic definitions

First, let's review some basic NAV terminology:

• Data type: This defines the kind of data that can be held in a field, whether it is a numeric (such as an integer or a decimal), text, table RecordID, time, date, Boolean, and so forth. The data type defines what constraints can be placed on the contents of a field, determines the functions in which the data element can be used (not all data types are supported by all functions), and defines what the results of certain functions will be.
• Fundamental data type: This is a simple, single-component structure that consists of a single value at any point in time, for example, a number, a string, or a Boolean value.
• Complex data type: This is a structure made up of or relating to simple data types, for example, records, program objects such as Pages or Reports, Binary Large OBjects (BLOBs), DateFormulas, external files, and indirect reference variables.
• Data Element: This is an instance of a data type that may be a Constant or a Variable.
• Constant: This is a data element that is explicitly defined in the code by a literal value. Constants are not modifiable during execution, only by a developer using C/SIDE. All the simple data types can be represented by constants. Examples are "MAIN" (Code or Text), 12.34 (Decimal), and "+01-312-444-5555" (Text).
• Variable: This is a data element that can have a value assigned to it dynamically during execution. Except for special cases, a variable will be a single, unchanging, and specific data type.