This section of the document is intended to be used by a programmer and analyst familiar with the programming language and provides a detailed discussion of more advanced features of the ProvideX language and environment. The topics discussed are as follows:

Tailoring ProvideX environment

ProvideX provides an initialization procedure and internal parameters that allows the environment to be customized. The parameters allow the user to change internal ProvideX settings and default operating modes. They are also used to control environmental emulation modes.

User-defined functions

The facility allows the programmer to define commonly used expressions or calculations as functions. These functions can then be referenced by name within the programs.

Subprograms

ProvideX allows for separately written programs to be called and executed from within a program. Two directives provide for the execution of subprograms. They are -- the CALL directive and the PERFORM directive.

Global Variables

The normal variable set is extended to allow for variables that will not be cleared except at the end of a session and are available to all subprograms.

Multi-keyed files

ProvideX provides the ability to have and maintain keyed files with up to 16 different access keys. Each of these 16 keys may consist of various data fields within the record and/or a portion of the external key. The KEYED directive is used to define these files.

Handling Non-ProvideX files

ProvideX can read and write almost any file on the system by directly accessing the disk sectors comprising the file's data elements. The ISZ= option of the OPEN directive is used to provide this function.

'Link' and 'Device' files

Special format LINK and DEVICE files can be created that allow for indirect file pointers (LINK files) or for device pointers (DEVICE files). Device files can also have device types associated with them to provide the application with complete device independence.

The PREFIX directive

If the files to be used exist on multiple disk drives or directories in the system, the PREFIX

directive allows for the definition of the file search rules.

Translation Tables

Translation tables can be used to convert data from one format to another with a minimum of effort.