Library Functions

Common C Library Functions

What are Library Functions?

Library Functions (also known as built-in functions) are functions that are already declared and defined in C header files (like <stdio.h>, <math.h>, and <string.h>).

To use them, you simply need to include the corresponding header file at the top of your program using the #include directive.

How to Use Them

        #include <header_name.h>

        // Inside main or any function:

        function_name(arguments);

Practical Examples by Category

1. Input/Output (`<stdio.h>`)

The most fundamental functions used for interacting with the user.

// printf() displays data; scanf() reads data
printf("Enter age: ");
scanf("%d", &age);

2. Mathematical Functions (`<math.h>`)

Used for advanced calculations like square roots or power functions.

double result = sqrt(25.0); // Returns 5.0
double p = pow(2, 3);      // Returns 8.0 (2 raised to 3)

3. String Handling (`<string.h>`)

Necessary for measuring or comparing text sequences.

char str[] = "SkillEco";
int len = strlen(str); // Returns the length of the string (8)

Important Note: When using math functions like sqrt() or pow(), ensure you use the %f or %lf format specifiers in printf, as these functions typically return floating-point values.

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