What is \'pch.h\' and why does it speed up compilation in Visual Studio?

Understanding the Essence of "pch.h" and Its Significance as the Initial Header File Inclusion

What is "pch.h"? The acronym "pch" stands for "precompiled header," a concept prevalent in the realm of computer programming. Essentially, a precompiled header is a C or C header file that undergoes compilation into an interim form, enabling rapid processing by the compiler. Employing precompiled headers can considerably shorten compilation time, proving particularly beneficial in handling extensive header files, those incorporating numerous other header files, or header files commonly included in various translation units.

Precompiled headers are championed for their role in expediting compilation. Specific compilers accommodate precompiling header files into a format accessible to the compiler more expeditiously. This intermediate format is referred to as a precompiled header, typically housed within a file bearing the extension ".pch" or comparable variations, such as ".gch" under the GNU Compiler Collection.

In the domain of Visual Studio, precompiled headers often take the moniker "pch.h" in the context of console-based applications; however, alternative naming conventions or abstention from its use is feasible. Project settings dictate which file, if any, qualifies as a precompiled header.

Visual Studio designates "pch.h" as the precompiled header when the compilation parameter /Yu is in play. Consequently, this development environment abstains from compiling any code preceding the "#include "pch.h" directive in the source file. The premise is that all code before and encompassing that specific line has already been compiled.

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