Functions of Standard Library in C

The C Standard Library contains a vast array of functions categorized into various headers, each serving different purposes. Below is a list of some commonly used Standard Library headers and a brief overview of their primary functions. Please note that this list is not exhaustive, as there are many more functions and headers available for various purposes.

1. stdio.h (Standard Input/Output):

   • printf(): Print formatted output to the console.
   • scanf(): Read formatted input from the console.
   • fopen(), fclose(), fread(), fwrite(): File I/O operations.
   • getchar(), putchar(): Read and write characters.

2. stdlib.h (Standard Library):

   • malloc(), calloc(), realloc(), free(): Dynamic memory allocation and deallocation.
   • rand(), srand(): Generate random numbers.
   • exit(): Terminate program execution.

3. string.h (String Manipulation):

   • strcpy(), strncpy(): Copy strings.
   • strcmp(), strncmp(): Compare strings.
   • strlen(): Calculate string length.
   • strcat(), strncat(): Concatenate strings.
   • strstr(): Find substring in a string.

4. math.h (Mathematical Functions):

   • sqrt(), pow(), exp(), log(): Mathematical operations.
   • sin(), cos(), tan(): Trigonometric functions.
   • ceil(), floor(): Round numbers up or down.
   • rand(), srand(): Random number generation.

5. ctype.h (Character Handling):

   • isalpha(), isdigit(), islower(), isupper(): Character classification.
   • tolower(), toupper(): Convert characters to lowercase or uppercase.

6. time.h (Date and Time):

   • time(): Get current time.
   • ctime(): Convert time to a string.
   • difftime(): Calculate time differences.
   • strftime(): Format time as a string.

7. stddef.h (Standard Definitions):

   • NULL: Null pointer constant.
   • size_t: Unsigned integer type used for sizes.

8. stdbool.h (Boolean Type):

   • bool: Boolean data type (true or false).

9. assert.h (Assertions):

   • assert(): Debugging aid to check program assumptions.

10. stdarg.h (Variable Argument Lists):

• va_start(), va_arg(), va_end(): Handle functions with a variable number of arguments (e.g., printf()).

11. signal.h (Signal Handling):

    • signal(): Set signal-handling functions.
    • raise(): Raise signals in the program.

12. locale.h (Locale and Internationalization):

    • setlocale(): Set the program's locale.
    • Functions for handling character encoding and internationalization.

13. errno.h (Error Handling):

    • errno: Global variable containing error codes.
    • Functions like perror() to handle errors gracefully.

14. stddef.h (Standard Definitions):

    • NULL: Null pointer constant.
    • size_t: Unsigned integer type used for sizes.

15. fcntl.h (File Control):

    • open(), close(), read(), write(): File I/O operations with low-level control.

16. sys/types.h and sys/stat.h (System Types and System Stat):

    • Data types and functions for dealing with system-related information and file attributes.

17. unistd.h (POSIX Operating System API):

    • Functions for interacting with the operating system, including process control and file operations.

18. math.h (Mathematical Functions):

    • fmod(), log10(), sinh(), cosh(), tanh(): Additional mathematical functions.

These are just some of the commonly used functions and headers from the C Standard Library. Each header contains a set of functions tailored to specific tasks, making C a versatile language for various programming needs. To utilize these functions, you typically include the relevant header at the beginning of your C source code file