1 Introduction

The ISO/ANSI C standard defines a library of functions, as well as related types and macros, to be provided with any implementation of ANSI C. The DEC C Language Reference Manual describes the ANSI-conformant library features common to all DEC C platforms. The DEC C Run-Time Library Reference Manual for OpenVMS Systems provides a more detailed description of these routines and their use in the OpenVMS environment. It also documents additional header files, functions, types, and macros that are available on the OpenVMS system.

All library functions are declared in a header file. To make the contents of a header file available to your program, include the header file with an #include preprocessor directive. For example:

#include <stdlib.h>

Each header file contains function prototypes for a set of related functions, and defines any types and macros needed for their use.

To list the header files on OpenVMS Alpha systems, use the following commands:

$ LIBRARY/LIST ALPHA$LIBRARY:SYS$STARLET_C.TLB  (Alpha only)

$ LIBRARY/LIST ALPHA$LIBRARY:DECC$RTLDEF.TLB  (Alpha only)

$ DIR SYS$COMMON:[DECC$LIB.REFERENCE.DECC$RTLDEF]*.H;  (Alpha only)

$ DIR ALPHA$LIBRARY:*.H;   (Alpha only)

The first command lists the text module form of the header files for the OpenVMS system interfaces. The second lists the text module form of the header files for the DEC C language interface. The third lists *.h header files for the DEC C language interfaces. The fourth lists *.h header files for layered products and other applications.

Note

The SYS$COMMON:[DECC$LIB.REFERENCE.DECC$RTLDEF] directory is only a reference area for your viewing. The compiler still looks in the *.TLB files for #include file searches.

To list the header files on OpenVMS VAX systems, use one of the following command:

$ DIR 'F$TRNLMN("DECC$LIBRARY_INCLUDE")'*.H;  (VAX only)
$ DIR DECC$LIBRARY_INCLUDE:*.H;  (VAX only)

On OpenVMS VAX systems, the following command might also find additional or duplicate header files:

$ DIR SYS$LIBRARY:*.H;  (VAX only)

However, duplicate files (such as <stdio.h>) found in SYS$LIBRARY probably support the VAX C Version 3.2 environment and should not be used with DEC C.

Function definitions themselves are not included in the header files, but are contained in the DEC C Run- Time Library (RTL) shipped with the OpenVMS operating system. Before using the DEC C RTL, you must be familiar with the following topics:

• The linking process

• The macro substitution process

• The difference between function definitions and function calls

• The format of valid file specifications

• The OpenVMS-specific methods of input and output (I/O)

• The DEC C for OpenVMS extensions and nonstandard features

A knowledge of all these topics is necessary to effectively use the DEC C RTL. This chapter shows the connections between these topics and the DEC C RTL. Read this chapter before any of the other chapters in this manual.

The primary purpose of the DEC C RTL is to provide a means for C programs to perform I/O operations; the C language itself has no facilities for reading and writing information. In addition to I/O support, the DEC C RTL also provides a means to perform many other tasks.

Chapters 2 through 11 describe the various tasks supported by the DEC C RTL. The Reference Section alphabetically lists and describes all the functions and macros available to perform these tasks.