HP C/iX Reference Manual (31506-90011)

4 Chapter1

Introduction

ANSI Mode

Unless you are writing code that must be recompiled on a system where ANSI C is not

available, it is recommended that you use the ANSI mode of compilation for your new

development. It is also recommended that you use ANSI mode to recompile existing

programs after making any necessary changes.

Because an ANSI-conforming compiler is required to do more thorough error detection and

reporting than has been traditional among C compilers, you may ﬁnd that your

productivity will be enhanced because more errors will be caught at compile time. This

may be especially true if you use the major new feature, function prototypes.

Non-ANSI Mode

You may not want to change your existing code, or you may have old code that relies on

certain non-ANSI features. Therefore, a non-ANSI mode of compilation has been provided.

In this mode, virtually all programs that compiled and executed under previous releases of

HP C/iX will continue to work as expected.

If you do not specify the mode of compilation, non-ANSI mode is the default. However, the

default mode will be changed to ANSI on some future release.

Focus of This Manual

This manual presents ANSI C as the standard version of the C language. Where certain

constructs are not available in non-ANSI mode, or would work differently, it is noted and

the differences are described.

HP C/iX, when invoked in ANSI mode, is intended to be a conforming implementation of

ANSI C, as speciﬁed by American National Standard X3.159. This manual uses the

terminology of that standard and attempts to explain the language deﬁned by that

standard, while also documenting the implementation decisions and extensions made in

HP C/iX. It is not the intent of this document to replicate the standard. Thus, you are

encouraged to refer to the standard for any ﬁne points of the language not covered here.