A data type can have a name, control type, keyable length, storage size, static values, a format and a composite definition. The Data Type Definition window is used to set the characteristics of a data type.
Each data type in your application must have a name. Typically, the name indicates the characteristics of the data type, such as the control type used or the size of the data type. For instance, the name String30 indicates that the data type has a string control type that can display 30 characters.
The control type determines the function of the data type and how it will store and display data. The control type is the main characteristic of a data type. Dexterity has a variety of control types; a comprehensive list of them can be found in the next section.
Some control types allow you to specify the keyable length of a data type, which is the number of characters a user can enter in a field with that particular data type. Control types such as currency, integer and string have a keyable length.
The storage size for a data type is the number of bytes needed to store a field using the data type in a table. The storage size is typically calculated by Dexterity and can’t be changed, except for string data types. The storage size for strings can be increased beyond the minimum amount calculated by Dexterity to allow room for expansion, in case you need to increase the keyable length of the data type.
Changing the storage size for a data type after you’ve entered data in an application may cause errors for existing records in a table. For instance, if you change the storage size for a data type used to store customer names, you won’t be able to read existing customer records until data in the table is converted. Data conversion is described in Updating an Application.
Static values are any text or pictures associated with a data type that are displayed by a field using that data type. They are described in detail in Static values.
A format contains extra characters, spacing and attributes that can be applied to a data type when data is entered or displayed.
A composite is a group of fields and their associated data types that are combined to form a single data type. Composites are described in Composites.