In this article, we discuss Header File List And Functions In C Language. Header files contain the set of predefined standard library functions that we can include in our c programs. But to use these various library functions, we have to include the appropriate header files. A header file has a .h extension that contains C function declarations and macro definition. There are two kinds of header files: the files that the developer writes and the files that come with your compiler. When we including a header file in a program, that means we copy the content of the header file.
syntax:
#include<file>
or
#include"file"
Header files include data types definitions, function prototypes, and C preprocessor commands. For example, we use function printf() in the program. then we have to include stdio.h in our C program.
Let’s see in detail how the compiler interprets the line.
#include<stdio.h>
Here, # is a pre-processor directive which tells us that this is the line which must be pre-processed by pre-processor.
include tells us that there is a filename ahead which must be included at the top of our program. Preprocessor simply copies contents of file stdio.h in our code.
<> – Angled brackets defines where to search for header files.
stdio.h – is the file to be included in our program so that we can use built-in functions in our program. These built-in functions are only declared in such header files and not defined.
Apart from method or class declarations, header files also contain predefined macros, data type definitions, etc.
When you call a built-in function, at compile time compiler compares your calling statement with function prototype(which is in the header file) and if the return type, function name, number of arguments, type of arguments are the same then only the result of comparison is said to be satisfying otherwise compiler gives you errors.
As we shown above we can create our own header files as well. But they are specified in between double quotes instead of angular brackets which will convene to make programming easier.
If you have a standard set of instructions that you want to insert in a lot of programs that you are writing then you can do it using the #include statement.
The # symbol at the start stipulate that this isn’t a C statement but one for the C pre-processor which looks at the text file before the compiler gets it. The #include tells the pre-processor to read in a text file and treat it as if it was part of the program’s text. For example:
#include “copy.txt”
could be used to include a copyright notice stored in the file copy.txt. However, the most common use of the #include is to define constants and macros. The C pre-processor is almost a language in its own right For example if you define the identifier NULL as:
#define NULL 0
then whenever you use NULL in your program the pre-processor substitutes 0. In most cases you want these definitions to be included in all your programs and so the obvious thing to do is to create a separate file that you can #include.
This idea of using standard include files has spiraled out of all proportions. Now such include files are called header files and they are distinguished by ending in the extension .h. A header file is generally used to define all of the functions, variables, and constants contained in any function library that you might want to use.
There are many header files in C programming language and there all header files have their own different functionalities…
List of all header file of c language as below.
List of header files in c language
| No. | Name | Description |
| 1 | stdio.h | Input/Output Functions |
| 2 | conio.h | console input/output |
| 3 | assert.h | Diagnostics Functions |
| 4 | ctype.h | Character Handling Functions |
| 5 | cocale.h | Localization Functions |
| 6 | math.h | Mathematics Functions |
| 7 | setjmp.h | Nonlocal Jump Functions |
| 8 | signal.h | Signal Handling Functions |
| 9 | stdarg.h | Variable Argument List Functions |
| 10 | stdlib.h | General Utility Functions |
| 11 | string.h | String Functions |
| 12 | time.h | Date and Time Functions |
| 13 | complex.h | A set of function for manipulating complex numbers |
| 14 | stdalign.h | For querying and specifying the alignment of objects |
| 15 | errno.h | For testing error codes |
| 16 | locale.h | Defines localization functions |
| 17 | stdatomic.h | For atomic operations on data shared between threads |
| 18 | stdnoreturn.h | For specifying non-returning functions |
| 19 | uchar.h | Types and functions for manipulating Unicode characters |
| 20 | fenv.h | A set of functions for controlling floating-point environment |
| 21 | wchar.h | Defines wide string handling functions |
| 22 | tgmath.h | Type-generic mathematical functions |
| 23 | stdarg.h | Accessing a varying number of arguments passed to functions |
| 24 | stdbool.h | Defines a boolean data type |
You can download a pdf file from here:
List of header files in c language pdf – v0.1
List of header files in c language pdf -v0.0
C Standard Library Functions
There are lots of standard library functions available in C to perform a lot of tasks easily. In a library, the actual functionality is implemented. For example, when we use any mathematics function we include math.h header file but in actual some math library libm.lib, libmmd.lib contain the body of the function. The standard library functions are built-in functions in C programming to handle tasks such as mathematical computations, I/O processing, string handling etc.you can also declare your own functions either in the program or in an external file with the .h extension called a header file.
- C Input Output Functions – transfer data between the C program and standard input/output devices.
| Function | Description |
| scanf | read character, string, numeric data from a keyboard |
| printf | print the “character, string, float, integer, octal and hexadecimal values” onto the output screen |
| getchar | reads a character from the terminal and returns it as an integer |
| putchar | displays the character passed to it on the screen |
| gets | reads a line from stdin(standard input) into the buffer |
| puts | writes the string str and a trailing newline to stdout. |
- C String Character Functions – String.h header file supports all the string functions in C language.
| Function | Description |
| strcat | concatenate two strings. |
| strchr | string scanning operation. |
| strcmp | compare two strings. |
| strcpy | copy a string. |
| strlen | get string length. |
| strncat | concatenate one string with part of another. |
| strncmp | compare parts of two strings. |
- C Time Date Localization Functions – implementing date and time manipulation operations.
| Function | Description | ||
| asctime | time is converted into a string. | ||
| clock | get current system time | ||
| ctime | return string that contains date and time information | ||
| difftime | get the difference between two given times | ||
| getdate | get the CPU time | ||
| gmtime | shares the tm structure that contains date and time information (UTC) | ||
| localtime | shares the tm structure that contains date and time information(Local-Time) | ||
| mktime | interprets tm structure as calendar time | ||
| setdate | modify the system date | ||
| strftime | modify the actual time format | ||
| time | get current system time as the structure | ||
- C Dynamic Memory Allocation Functions – dynamic memory allocation defined as the process of allocating memory during program execution.
| Function | Description |
| malloc | Allocates requested size of bytes and returns a pointer first byte of allocated space |
| calloc | Allocates space for an array of elements initializes to zero and then returns a pointer to memory |
| free | deallocate the previously allocated space |
| realloc | Change the size of the previously allocated space |
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