gtpa2m0eApplication Programming

Program Categories

This document makes the distinction between two categories of TPF programs: ECB and non-ECB controlled programs. An application program as discussed in this document means any user-developed program designed to run online under TPF that is not a part of the TPF system itself. When used in this document, an application program always implies an ECB-controlled program as defined in the following section.

C Language in the Control Program

The TPF control program does not support C language programs. The implementation of C requires ECB virtual memory (EVM) and register connection to an ECB.

ECB-Controlled Programs

An ECB-controlled program consists of 1 or more program segments. Assembler language and TARGET(TPF) programs must fit into a standard TPF main storage block. For practical purposes ISO-C programs have no size limit. ECB-controlled programs can be permanently assigned to main storage during online execution of the TPF system, or allocated to file storage and loaded into main storage at execution.

Main storage resident ECB-controlled programs are allocated as core resident. Core resident programs are ECB-controlled programs that are permanently allocated to main storage because they are used so frequently.

TPF publications also refer to ECB-controlled programs as file-resident, real-time, and E-type programs.

Non-ECB Controlled Programs

The programs that constitute the main storage resident portion of the TPF system are not required to fit into standard TPF fixed size storage blocks or to use an entry control block. Although assigned to file storage for restart purposes, these programs always are resident in main storage. TPF publications sometimes call these programs C-type programs.

Offline programs run under control of either TPF or MVS to provide function in support of the online portion of the TPF system. TPF publications often refer to these programs either as S-type (system installation) or as V-type (other offline) programs.