What is a Preprocessor Directive?

PreProcessor directives are lines covered in a program that begin with the Character #, which lead them to one-of-a-kind from an average supply Code text. They are invoked by means of the Compiler to sySTEM a few programs earlier than compilation. Preprocessor directives cHange the textual content of the Source Code and the end result is a new source code with out these directives.

Although preprocessing in C# is conceptually much like that in C/C , it is distinctive in Components. First, preprocessing in C# does now not contain a separate step for preprocessor execution earlier than compilation. It is processed as part of the Lexical Analysis phase. Second, it can't be used to create Macros. In addition, the brand new directives #viciNity and #unregion had been delivered in C# along with the exclusion of a few directives used in advance (#include is a outstanding directive whose use is replaced with "using" to include assemblies).

Java does not aid preprocessor directives.

What Does Preprocessor Directive Mean?

A preprocessor directive is commonly positioned inside the pinnacle of the source code in a separate line beginning with the character "#", observed by way of directive call and an non-compulsory white space before and after it. Because a Comment on the identical line of Statement of the preprocessor directive has for use and cannot scroll via the following line, delimited Feedback can not be used. A preprocessor directive announcement must no longer quit with a semicolon (;). Preprocessor directives may be defined in source code or inside the not unusual line as argument for the duration of compilation.

Examples for preprocessing directives that can be utilized in C# consist of:

• #define and #undef: To define and undefine conditional compilation symbols, respectively. These symbols could be checked at some point of compilation and the specified phase of supply code can be Compiled. The scope of a image is the document wherein it is described.
• #if, #elif, #else, and #endif: To pass part of supply code primarily based on conditions. Conditional sections can be nested with directives Forming complete sets.
• #line: To control line numbers generated for errors and warning. This is mostly used by Meta-Programming equipment to generate C# supply code from a few textual content enter. It is typically used to modify the road numbers and supply File names pronounced by way of the compiler in its Output.
• #errors and #caution : To generate errors and warnings, respectively. #error is used to forestall compilation, while #caution is used to continue compilation with messages within the Console.
• #place and #endregion :To explicitly mark sections of source code. These permit enlargement and disintegrate inner Visual Studio for higher readability and reference.