C Header Files and Standard Functions (This info is taken from Appendix C of the nice book Data Abstraction and Problem Solving with C, 3rd ed., by F. Carrano & J.J. Prichard.) Here is a list of commonly used C headers. If an older version of the header exists, its name is shown in parentheses. Cassert (assert.h). C compatibility headers. For some of the C standard library headers of the form xxx. H, the C standard library both includes an identically-named header and another header of the form cxxx (all meaningful cxxx headers are listed above). With the exception of complex. H header included in the C standard library places in the global namespace each name that the corresponding.
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Apr 06, 2011 73 videos Play all C Programming Tutorials Playlist thenewboston Mix Play all Mix - thenewboston YouTube 101 Tips & Tricks for OSRS - Duration: 21:58. Mar 07, 2018 The instructions here are as per version 4.9.9.2 of Dev C. I don’t think there will be much changes in any older version. So here we go: 1. Go to the Tools menu.
Mar 06, 2018 The instructions here are as per version 4.9.9.2 of Dev C. I don’t think there will be much changes in any older version. So here we go: 1. Go to the Tools menu. In the Tools menu, you should find and option called Compiler Options. Header Files in C. Header files contain definitions of Functions and Variables, which is imported or used into any C program by using the pre-processor #include statement.Header file have an extension '.h' which contains C function declaration and macro definition.
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A header file is a file with extension .h which contains C function declarations and macro definitions to be shared between several source files. There are two types of header files: the files that the programmer writes and the files that comes with your compiler.
You request to use a header file in your program by including it with the C preprocessing directive #include, like you have seen inclusion of stdio.h header file, which comes along with your compiler.
Including a header file is equal to copying the content of the header file but we do not do it because it will be error-prone and it is not a good idea to copy the content of a header file in the source files, especially if we have multiple source files in a program.
A simple practice in C or C++ programs is that we keep all the constants, macros, system wide global variables, and function prototypes in the header files and include that header file wherever it is required.
Dev Cpp Header Files
Include Syntax
Both the user and the system header files are included using the preprocessing directive #include. It has the following two forms −
This form is used for system header files. It searches for a file named 'file' in a standard list of system directories. You can prepend directories to this list with the -I option while compiling your source code.
This form is used for header files of your own program. It searches for a file named 'file' in the directory containing the current file. You can prepend directories to this list with the -I option while compiling your source code.
Include Operation
The #include directive works by directing the C preprocessor to scan the specified file as input before continuing with the rest of the current source file. The output from the preprocessor contains the output already generated, followed by the output resulting from the included file, followed by the output that comes from the text after the #include directive. For example, if you have a header file header.h as follows −
and a main program called program.c that uses the header file, like this −
the compiler will see the same token stream as it would if program.c read.
Once-Only Headers
If a header file happens to be included twice, the compiler will process its contents twice and it will result in an error. The standard way to prevent this is to enclose the entire real contents of the file in a conditional, like this −
This construct is commonly known as a wrapper #ifndef. When the header is included again, the conditional will be false, because HEADER_FILE is defined. The preprocessor will skip over the entire contents of the file, and the compiler will not see it twice.
Computed Includes
Sometimes it is necessary to select one of the several different header files to be included into your program. For instance, they might specify configuration parameters to be used on different sorts of operating systems. You could do this with a series of conditionals as follows −
But as it grows, it becomes tedious, instead the preprocessor offers the ability to use a macro for the header name. This is called a computed include. Instead of writing a header name as the direct argument of #include, you simply put a macro name there −
SYSTEM_H will be expanded, and the preprocessor will look for system_1.h as if the #include had been written that way originally. SYSTEM_H could be defined by your Makefile with a -D option.
-->The names of program elements such as variables, functions, classes, and so on must be declared before they can be used. For example, you can't just write x = 42 without first declaring 'x'.
The declaration tells the compiler whether the element is an int, a double, a function, a class or some other thing. Furthermore, each name must be declared (directly or indirectly) in every .cpp file in which it is used. When you compile a program, each .cpp file is compiled independently into a compilation unit. The compiler has no knowledge of what names are declared in other compilation units. That means that if you define a class or function or global variable, you must provide a declaration of that thing in each additional .cpp file that uses it. Each declaration of that thing must be exactly identical in all files. A slight inconsistency will cause errors, or unintended behavior, when the linker attempts to merge all the compilation units into a single program.
To minimize the potential for errors, C++ has adopted the convention of using header files to contain declarations. You make the declarations in a header file, then use the #include directive in every .cpp file or other header file that requires that declaration. The #include directive inserts a copy of the header file directly into the .cpp file prior to compilation.
Note
In Visual Studio 2019, the C++20 modules feature is introduced as an improvement and eventual replacement for header files. For more information, see Overview of modules in C++.
Example
The following example shows a common way to declare a class and then use it in a different source file. We'll start with the header file, my_class.h. It contains a class definition, but note that the definition is incomplete; the member function do_something is not defined:
Next, create an implementation file (typically with a .cpp or similar extension). We'll call the file my_class.cpp and provide a definition for the member declaration. We add an #include directive for 'my_class.h' file in order to have the my_class declaration inserted at this point in the .cpp file, and we include <iostream> to pull in the declaration for std::cout. Note that quotes are used for header files in the same directory as the source file, and angle brackets are used for standard library headers. Also, many standard library headers do not have .h or any other file extension.
In the implementation file, we can optionally use a using statement to avoid having to qualify every mention of 'my_class' or 'cout' with 'N::' or 'std::'. Don't put using statements in your header files!
Now we can use my_class in another .cpp file. We #include the header file so that the compiler pulls in the declaration. All the compiler needs to know is that my_class is a class that has a public member function called do_something().
After the compiler finishes compiling each .cpp file into .obj files, it passes the .obj files to the linker. When the linker merges the object files it finds exactly one definition for my_class; it is in the .obj file produced for my_class.cpp, and the build succeeds.
List Of C++ Header Files
Include guards
Dev C++ Header Files List Windows 10
Typically, header files have an include guard or a #pragma once directive to ensure that they are not inserted multiple times into a single .cpp file.
What to put in a header file
Header File In C
Because a header file might potentially be included by multiple files, it cannot contain definitions that might produce multiple definitions of the same name. The following are not allowed, or are considered very bad practice:
- built-in type definitions at namespace or global scope
- non-inline function definitions
- non-const variable definitions
- aggregate definitions
- unnamed namespaces
- using directives
Use of the using directive will not necessarily cause an error, but can potentially cause a problem because it brings the namespace into scope in every .cpp file that directly or indirectly includes that header.
Sample header file
C++ Header Files Pdf
The following example shows the various kinds of declarations and definitions that are allowed in a header file: