What is stdafx.h and How Does it Speed Up Compilation in Visual Studio?

stdafx.h: Precompiled Headers for Accelerated Compilation

stdafx.h plays a crucial role in Microsoft Visual Studio projects, contributing to faster compilation times. It serves as a precompiled header, consolidating frequently included but rarely modified system and project-specific files.

What is stdafx.h?

stdafx.h is generated by Visual Studio wizards. It defines a collection of headers that are commonly used throughout a project but remain relatively unchanged. These headers include system headers such as iostream and windows.h, as well as project-specific headers.

Benefits of Precompiled Headers

Visual C optimizes compilation by precompiling stdafx.h before processing the source code. This precompilation enables compilers like Visual C 6.0 and later to significantly reduce overall compilation times.

Visual C Compilation Behavior

By default, Visual C skips compilation of code preceding the #include "stdafx.h" directive in the source file. This behavior is governed by the /Yu'stdafx.h' option. If this option is unchecked, the compiler will compile all code before the #include statement.

Precompiled Header Limitations

It's important to note that Visual C treats code before the #include "stdafx.h" directive as if it has already been compiled. Modifying this code or using header files that contradict the precompiled header may lead to compilation errors.

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