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List of C Header File with Detailed Explanations



This Chapter is intended to clear your fundamental concepts with the help of numerous programming problems. The programs are mapped out in such a way that with each step you will move towards perfectionism. It’s highly recommended to do every program with the pen and paper for enhancing your programming concepts efficiently.


Standard Library Functions - Header File

In the C Programming Language, the Standard Library Functions are divided into several header files.

Below is the list of header files that we will cover:

Header Files

  • <assert.h> Diagnostics Functions

  • <ctype.h> Character Handling Functions

  • <locale.h> Localization Functions

  • <math.h> Mathematics Functions

  • <setjmp.h> Nonlocal Jump Functions

  • <signal.h> Signal Handling Functions

  • <stdarg.h> Variable Argument List Functions

  • <stdio.h> Input/Output Functions

  • <stdlib.h> General Utility Functions

  • <string.h> String Functions

  • <time.h> Date and Time Functions


Standard Library Functions - ctype.h

In the C Programming Language, the Standard Library Functions are divided into several header files.

The following is a list of functions found within the <ctype.h> header file:

Character Testing functions

  • isalnum Test for Alphanumeric

  • isalpha Test for Alphabetic

  • iscntrl Test for Control Character

  • isdigit Test for Digit

  • isgraph Test for Graphical Character (does not include a space).

  • islower Test for Lowercase Letter

  • isprint Test for Printing Character (does include a space).

  • ispunct Test for Punctuation Character

  • isspace Test for White-Space Character

  • isupper Test for Uppercase Letter

  • isxdigit Test for Hexadecimal Digit

Character Case-Mapping functions

  • Tolower Convert to Lowercase

  • Toupper Convert to Uppercase


Standard Library Functions - locale.h

In the C Programming Language, the Standard Library Functions are divided into several header files.

The following is a list of functions found within the <locale.h> header file:

Localization functions

  • localeconv Get Locale Conventions

  • setlocale Set Locale


Standard Library Functions - math.h

In the C Programming Language, the Standard Library Functions are divided into several header files.

The following is a list of functions found within the <math.h> header file:

Absolute Value functions

  • Fabs Absolute Value of Floating-Point Number

Nearest Integer, Absolute Value, and Remainder functions

  • ceil Ceiling

  • floor Floor

  • fmod Floating Modulus

Exponential and Logarithmic functions

  • exp Exponential

  • frexp Split into Fraction and Exponent

  • ldexp Combine Fraction and Exponent

  • log Natural Logarithm

  • log10 Common Logarithm

  • modf Split into Integer and Fractional Parts

Power functions

  • pow Power

  • sqrt Square Root

Trigonometric functions

  • acos Arc Cosine

  • asin Arc Sine

  • atan Arc Tangent

  • atan2 Arc Tangent of Quotient

  • cos Cosine

  • sin Sine

Hyperbolic functions

  • cosh Hyperbolic Cosine

  • sinh Hyperbolic Sine

  • tanh Hyperbolic Tangent



Standard Library Functions - setjmp.h

In the C Programming Language, the Standard Library Functions are divided into several header files.

The following is a list of functions found within the <setjmp.h> header file:

Nonlocal Jump functions

  • longjmp Nonlocal Jump

  • setjmp Prepare for Nonlocal Jump


Standard Library Functions - signal.h

In the C Programming Language, the Standard Library Functions are divided into several header files.

The following is a list of functions found within the <signal.h> header file:

Signal Handling functions

  • raise Raise Signal

  • signal Install Signal Handler


Standard Library Functions - stdarg.h

In the C Programming Language, the Standard Library Functions are divided into several header files.

The following is a list of functions found within the <stdarg.h> header file:

Variable Argument List functions

  • va_arg Fetch Argument from Variable Argument List

  • va_end End Processing of Variable Argument List

  • va_start Start Processing of Variable Argument List


Standard Library Functions - stdio.h

In the C Programming Language, the Standard Library Functions are divided into several header files.

The following is a list of functions found within the <stdio.h> header file:

Formatted Input/Output functions

  • fprintf Formatted File Write

  • fscanf Formatted File Read

  • printf Formatted Write

  • scanf Formatted Read

  • sprintf Formatted String Write

  • sscanf Formatted String Read

  • vfprintf Formatted File Write Using Variable Argument List

  • vprintf Formatted Write Using Variable Argument List

  • vsprintf Formatted String Write Using Variable Argument List

File Operation functions

  • fclose Close File

  • fflush Flush File Buffer

  • fopen Open File

  • freopen Reopen File

  • remove Remove File

  • rename Rename File

  • setbuf Set Buffer (obsolete)

  • setvbuf Set Buffer

  • tmpfile Create Temporary File

  • tmpnam Generate Temporary File Name

Character Input/Output functions

  • fgetc Read Character from File

  • fgets Read String from File

  • fputc Write Character to File

  • fputs Write String to File

  • getc Read Characters from File

  • getchar Read Character

  • gets Read String

  • putc Write Character to File

  • putchar Write Character

  • puts Write String

  • ungetc Unread Character

Block Input/Output functions

  • fread Read Block from File

  • fwrite Write Block to File

File Positioning functions

  • fgetpos Get File Position

  • fseek File Seek

  • fsetpos Set File Position

  • ftell Determine File Position

  • rewind Rewind File

Error Handling functions

  • clearer Clear Stream Error

  • feof Test for End-of-File

  • ferror Test for File Error

  • perror Print Error Message


Standard Library Functions - stdlib.h

In the C Programming Language, the Standard Library Functions are divided into several header files.

The following is a list of functions found within the <stdlib.h> header file:

Communication with the Environment functions

  • abort Abort Program

  • atexit Register Function to be Called at Program Exit

  • exit Exit from Program

  • getenv Get Environment String

  • system Perform Operating System Command

Integer Arithmetic functions

  • abs Absolute Value of Integer

  • div Integer Division

  • labs Absolute Value of Long Integer

  • ldiv Long Integer Division

Pseudo-Random Sequence Generation functions

  • rand Generate Pseudo-Random Number

  • srand Seed Pseudo-Random Number Generator

String Conversion functions

  • atof Convert String to Floating-Point

  • atoi Convert String to Integer

  • atol Convert String to Long Integer

  • strtod Convert String to Double

  • strtol Convert String to Long Integer

  • strtoll Convert String to Long Long

  • strtoul Convert String to Unsigned Long Integer

Searching and Sorting functions

  • bsearch Binary Search

  • qsort Sort Array

Dynamically Allocated Array functions

  • calloc Allocate and Clear Memory Block

  • malloc Allocate Memory Block

  • realloc Resize Memory Block

Deallocating Storage functions

  • free Free Memory Block

Multibyte Character functions

  • mblen Compute Length of Multibyte Character

  • mbtowc Convert Multibyte Character to Wide Character

  • wctomb Convert Wide Character to Multibyte Character

Multibyte String functions

  • mbstowcs Convert Multibyte String to Wide Character String

  • wcstombs Convert Wide Character String to Multibyte String


Standard Library Functions - string.h

In the C Programming Language, the Standard Library Functions are divided into several header files.

The following is a list of functions found within the <string.h> header file:

Comparison functions

  • memcmp Compare Memory Blocks

  • strcmp String Compare

  • strcoll String Compare Using Locale-Specific Collating Sequence

  • strncmp Bounded String Compare

  • strxfrm Transform Locale-Specific String

Concatenation functions

  • strcat String Concatenation

  • strncat Bounded String Concatenation

Copying functions

  • memcpy Copy Memory Block

  • memmove Copy Memory Block

  • strcpy String Copy

  • strncpy Bounded String Copy

Search functions

  • memchr Search Memory Block for Character

  • strchr Search String for Character

  • strcspn Search String for Intial Span of Characters Not in Set

  • strpbrk Search String for One of a Set of Characters

  • strrchr Search String in Reverse for Character

  • strspn Search String for Initial Span of Characters in Set

  • strstr Search String for Substring

  • strtok Search String for Token

Miscellaneous functions

  • memset Initialize Memory Block

  • strerror Convert Error Number to String

  • strlen String Length


Standard Library Functions - time.h

In the C Programming Language, the Standard Library Functions are divided into several header files.

The following is a list of functions found within the <time.h> header file:

Time Conversion functions

  • asctime Convert Date and Time to ASCII

  • ctime Convert Date and Time to String

  • gmtime Convert to Greenwich Mean Time

  • localtime Convert to Local Time

  • mktime Convert to Calendar Time

  • strftime Write Formatted Date and Time to String

Time Manipulation functions

  • clock Processor Clock

  • difftime Time Difference

  • time Current Time

Copying functions

  • memcpy Copy Memory Block

  • memmove Copy Memory Block

  • strcpy String Copy

  • strncpy Bounded String Copy


List of inbuilt C functions in conio.h file:

  • clrscr() This function is used to clear the output screen.

  • getch() It reads character from keyboard

  • getche() It reads character from keyboard and echoes to o/p screen

  • textcolor() This function is used to change the text color

  • textbackground() This function is used to change text background



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