Concept header files c

In this tutorial, you will be learning about C header files and how these header files can be included in your C program and how it works within your C language. Header files are helping file of your C program which holds the definitions of various functions and their associated variables that needs to be imported into your C program with the help of pre-processor include statement.

All the header file have a '. In other words, the header files can be requested using the preprocessor directive include. The default header file that comes with the C compiler is the stdio.

Including a header file means that using the content of header file in your source program. The basic syntax of using these header files is:. This kind of file inclusion is implemented for including system oriented header files. This technique with angular braces searches for your file-name in the standard list of system directories or within the compiler's directory of header files.

Whereas, the second kind of header file is used for user-defined header files or other external files for your program. Study Resources. Log In. Components of a header file Types of header files Working of header files Commonly used header files Function declaration Compilation process The preprocessor and its directives Context and Application Practice Problems Common Mistakes Related Concepts.

What is a header file? Components of a header file Any header file has 3 components: 1. Types of header files The two types of header files are: Pre-defined header file: Files that already exist in the compiler are called pre-defined header files. User-defined header file: Files defined by the user itself are called user-defined header files.

Working of header files The source file contains include, which is a command that instructs the compiler to process the files before compilation. Commonly used header files Below are some important header files along with their usage. It includes stream objects like cout and cin for giving output and taking input. It indicates the beginning of the variable-length argument list and takes the arguments from the variable-length argument list within the program.

Further, these limit the variable from storing any value from the specified limits. For instance, an unsigned character stores up to places. Function declaration A block of code, which is called from another location in a C program or any other high-level language program or class, is known as the declaration of a function.

Function prototype Function prototype contains the declaration of a function that includes the name of parameters, the data type of parameters and the return type of the function. Compilation process The compiler is used to compile a computer program.

The preprocessor and its directives A preprocessor is a program that processes the code before passing it to the compiler. Preprocessor directive Description Example include This statement includes another file into the current file.

A macro is a program segment that is replaced by the macro value. Syntax: define identifier token-string define Pi 3. Syntax: undef identifier undef Pi if This directive is used when a particular condition needs to be checked before the execution of a program. The preprocessor checks the condition, and if it is true, the code will be executed.

It first checks if the macro is defined. If it defined it will return true. When the statement evaluates to true, it includes an alternative source code. Syntax: else else endif This statement is used to end the if, ifdef, and ifndef code blocks. Syntax: endif endif error This directive returns an error message when a fatal error is encountered and stops preprocessing.

It is used to offer operating system features. Syntax: pragma token pragma exit func. Context and Application This topic is significant in the professional exams for undergraduate, graduate, and post-graduate courses Bachelors in Science in Computer Science Masters in Science in Computer Science.

Practice Problems Q1. Which of the following is the correct description of stdio. It includes all standard library functions It includes all input and output functions It includes all mathematical functions It contains floating-point functions that return 0. Answer: Option b Explanation : stdio. Which of the following is used to mark a preprocessor directive?

Which of the following is the file that is defined by the user itself? User-defined header Predefined header error-prone header function declarations Answer: Option a Explanation : Files that are defined by the user itself are called user-defined header files. 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 ". Each header file contains information or declarations for a particular group of functions. Like stdio. Similarly, the header file math. When we want to use any function in our c program then first we need to import their definition from c library, for importing their declaration and definition we need to include header file in program by using include.

Header file include at the top of any C program.