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1. • • The “#include” preprocessor directs the compiler that the header file needs to be processed before compilation and includes all the necessary data types and function definitions.
     www.geeksforgeeks.org › header-files-in-c-cpp-and-its-uses

     Header Files in C - GeeksforGeeks

2. Top results related to why do some c programmers use the #include facility data

   • Why do some kernel programmers use goto instead of simple while loops?

     Top Answer

     Answered Oct 21, 2012 · 33 votes

     In the case of this example, I suspect it was about retrofitting SMP support into code that was originally written in a non-SMP-safe way. Adding a goto again; path is a lot simpler and less invasive than restructuring the function.

     I can't say I like this style much, but I also think it's misguided to avoid goto for ideological reasons. One special case of goto usage (different from this example) is where goto is only used to move forward in a function, never backwards. This class of usages never results in loop constructs arising out of goto, and it's almost always the simplest, clearest way to implement the needed behavior (which is usually cleaning up and returning on error).

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     1/5

   • Why do projects use the -I include switch given the dangers?

     Top Answer

     Answered Nov 05, 2018 · 33 votes

     What legitimate reasons are there for -I over -iquote? -I is standardized (at least by POSIX) while -iquote isn't. (Practically, I'm using -I because tinycc (one of the compilers I want my project to compile with) doesn't support -iquote.)

     How do projects manage with -I given the dangers? You'd have the includes wrapped in a directory and use -I to add the directory containing that directory.

     • filesystem: includes/mylib/endian.h
     • command line: -Iincludes
     • C/C++ file: #include "mylib/endian.h" //or <mylib/endian.h>

     With that, as long as you don't clash on the mylib name, you don't clash (at least as far header names are concerned).

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     2/5

   • Why do some compilers use "a.out" as the default name for executables?

     Top Answer

     Answered Aug 02, 2009 · 46 votes

     a.out stands for assembler output. I think that justifies why most compilers have this name as default. More info here.

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     3/5

   • Why do C++ templates use the angle bracket syntax?

     Top Answer

     Answered Apr 11, 2017 · 97 votes

     Templates were introduced in the 1988 USENIX paper Parameterized Types for C++ by Bjarne Stroustrup, later incorporated into The Annotated C++ Reference Manual published in 1990 (the version before standardized C++). According to the paper,

     The <…> brackets are used in preference to the parentheses (…) partly to emphasize the different nature of template arguments (they will be evaluated at compile time) and partly because parentheses are already hopelessly overused in C++.

     …

     But why use brackets instead of parentheses? As mentioned before, parentheses already have many uses in C++. A syntactic clue (the <…> brackets) can be usedful for reminding the user about the different nature of the type parameters (they are evaluated at compile time). Furthermore, the use of parentheses could lead to pretty obscure code:

     template(int sz = 20) class buffer { buffer(int i = 10); // ...};buffer b1(100)(200);buffer b2(100); // b2(100)(10) or b2(20)(100)?buffer b3; // legal?-

     These problems would become a serious practical concern if the notation for explicit disambiguation of overloaded function calls were adopted. The chosen alternative seems much cleaner:

     template<int sz = 20> class buffer { buffer(sz)(int i = 10); // ...};buffer b1<100>(200);buffer b2<100>; // b2<100>(10)buffer b3; // b3<20>(10)buffer b4(100); // b4<20>(100)-

     The paper also explained why the template and class keywords are used.

     Note that the Stroustrup placed the <…> after the variable name in the same manner as int x[10] to argue against (…), though this placement is never used elsewhere in the paper.

     His argument that "using (…) can lead to obscure/ambiguous code" is still valid though. As mentioned in this question's comment, using parenthesis T(x) leads to ambiguity with function type or function call (note that T can be a function template and C++ allowed values to be template arguments).

     Similarly, using square brackets T[x] leads to ambiguity with array type or indexing.

     I don't see why T{x} cannot be used yet, maybe it was simply not considered, or maybe it is too ugly to have {…} used everywhere.

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     4/5

   • Why do some developer use 'http' and 'express' to create the server?

     Top Answer

     Answered Jul 04, 2016 · 12 votes

     No meaningful difference. In fact, if you look at the code for app.listen(), all it does is do http.createServer() and than call .listen() on it. It's just meant to be a shortcut that saves you using the http module directly.

     Here's the code for app.listen()

     :

     app.listen = function listen() { var server = http.createServer(this); return server.listen.apply(server, arguments);};

     Your second code block is just a bit less code because it uses the app.listen() shortcut. Both do the same.

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     5/5

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3. People also ask

   How to include a file in a program?

   • We use #include directive to include contents of another file (especially header file’s) to a program. We can include a file in two different ways. This variant of including header file, searches header file in the “standard header file directory”. Standard header file directory is the path where all header files are stored.

   C preprocessor directives - #include, #define, #undef and conditional

   codeforwin.org/c-programming/c-preprocessor-directives-include-define-undef-conditional-directives

   See all results for this question

   How to use #include in C program?

   • There are two variations of how we can use #include in our C program. 1. Including using <> It is mainly used to access pre-existing system header files located in the standard system directories. While importing a file using angular brackets (<>), the preprocessor uses a predetermined directory path to access the file. 2. Including using ” “

   #include in C - GeeksforGeeks

   www.geeksforgeeks.org/c-c-include-directive-with-examples/

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   What is a 'include' command in C?

   • This directive is always placed at the beginning of a C program and it is a preprocessor command that tell the compiler to include the contents of the file specified after #include directive. There are two types of files that can be included: pre-existing system header files and user-defined header files.

   #include in C - GeeksforGeeks

   www.geeksforgeeks.org/c-c-include-directive-with-examples/

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   What is 'INCLUDE preprocessor' in C?

   • The #include preprocessor directive is read by the preprocessor and instructs it to insert the contents of a user-defined or system header file in our C program. These files are mainly imported from outside header files. The process of importing such files that might be system-defined or user-defined is known as File Inclusion.

   #include in C - GeeksforGeeks

   www.geeksforgeeks.org/c-c-include-directive-with-examples/

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4. stackoverflow.com › questions › 5735379c - What does #include actually do? - Stack Overflow

   stackoverflow.com › questions › 5735379

   • Cached

   Not really, no. The compiler saves the original file descriptor on a stack and opens the #included file; when it reaches the end of that file, it closes it and pops back to the original file descriptor. That way, it can nest #included files almost arbitrarily.

   • Logically, that copy/paste is exactly what happens. I'm afraid there isn't any more to it. You don't need the ; , though. Your specific example...
   • That (copy/paste) is exactly what #include "header.h" does. Note that it will be different for #include or when the compiler can't f...
   • Not really, no. The compiler saves the original file descriptor on a stack and opens the #include d file; when it reaches the end of that file, i...
   • The # include statement "grabs the attention" of the pre-processor (the process that occurs before your program is actually compiled) and "tells"...
   • It's part of the preprocessor. Have a look at http://en.wikipedia.org/wiki/C_preprocessor#Including_files . And yes, it's just copy and paste.
   • This is a nice link to answer this question. http://msdn.microsoft.com/en-us/library/36k2cdd4.aspx Usually #include and #include "path-name" just d...

5. stackoverflow.com › questions › 464560c++ - How to use #include directive correctly? - Stack Overflow

   stackoverflow.com › questions › 464560

   • Cached

   You use #include "yourfile.h" if yourfile.h is in the current working directory and #include <yourfile.h> if the path to yourfile.h file was included in the C++ include directories (somewhere in configuration, example: c:\mylib\yourfile.h, the path c:\mylib\ has to be specified as an include directory) Also you can include .cpp and .hpp (h plus ...

   Code sample

   # include < h-char-sequence> new-line

   searches a sequence of implementation-de?ned places for a header identi?ed

   uniquely by the speci?ed sequence between the < and > delimiters, and

   causes the replacement of that directive by the entire contents of the

   header. How the places are speci?ed or the header identi?ed is...

   See more on stackoverflow

6. www.geeksforgeeks.org › c-c-include-directive-with#include in C - GeeksforGeeks

   www.geeksforgeeks.org › c-c-include-directive-with

   • Cached

   Jan 8, 2024 · In C programming, the #include directive is very important to integrate any external files (header files) into a program. This directive is always placed at the beginning of a C program and it is a preprocessor command that tell the compiler to include the contents of the file specified after #include directive.

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8. cplusplus.com › articles › Gw6AC542Headers and Includes: Why and How - C++ Articles - C++ Users

   cplusplus.com › articles › Gw6AC542

   • Cached

   This article is meant to address a common newbie problem regarding failure to understand #include, headers, and source file interaction. Several good practices are outlined and explained to show how to avoid some ugly snags.

9. codeforwin.org › c-programming › c-preprocessorC preprocessor directives - #include, #define, #undef and ...

   codeforwin.org › c-programming › c-preprocessor

   • Cached

   Nov 18, 2018 · We use #include directive to include contents of another file (especially header file’s) to a program. We can include a file in two different ways. #include <file.h> This variant of including header file, searches header file in the “standard header file directory”. Standard header file directory is the path where all header files are stored.

10. www.techonthenet.com › c_language › directivesC Language: #include Directive - TechOnTheNet

    www.techonthenet.com › c_language › directives

    In the C Programming Language, the #include directive tells the preprocessor to insert the contents of another file into the source code at the point where the #include directive is found. Include directives are typically used to include the C header files for C functions that are held outsite of the current source file. Syntax.

11. stackoverflow.com › questions › 35720656How does #include work in C++? - Stack Overflow

    stackoverflow.com › questions › 35720656

    • Cached

    Mar 1, 2016 · The preprocessor #include directive does exactly what the name implies, it actually includes the file at the place of the directive. Simple example: Lets say we have to files, first a header file named a.h. // Stuff for the class. Then a source file a.cpp: // Code. The preprocessor generates a single file looking like.