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C Standard Library Functions

C Standard Library Functions

  • C is a popular programming language that comes with a standard library that provides various functions for performing common tasks.
  • These functions are included in various header files, each serving a specific purpose.

Standard Library Functions in C

  • stdio.h
  • stdlib.h
  • conio.h
  • ctype.h
  • math.h
  • string.h

<stdio.h> - Input/Output Functions

The stdio.h header file provides functions for standard input and output operations.
Example: Printing to the Console
1#include <stdio.h>
2
3int main() {
4    printf("Hello, World!\n");
5    return 0;
6}
7
Explanation:
  • #include <stdio.h>: This line includes the standard I/O header.
  • printf(): This function is used to print text to the console.
  • "\n": Represents a newline character for formatting.

<stdlib.h> - Standard Library Functions

The stdlib.h header file provides functions for general-purpose tasks.
Example: Using rand() to Generate Random Numbers
1#include <stdio.h>
2#include <stdlib.h>
3#include <time.h>
4
5int main() {
6    srand(time(NULL)); // Seed the random number generator
7    int random_number = rand() % 100; // Generate a random number between 0 and 99
8    printf("Random Number: %d\n", random_number);
9    return 0;
10}
11
Explanation:
  • srand(time(NULL)): Seeds the random number generator with the current time, ensuring different sequences of random numbers each time you run the program.
  • rand(): Generates a random numbers
  • % 100: Limits the range to 0-99.

<conio.h> - Console Input/Output Functions (DOS/Windows)

  • Note: <conio.h> is not a part of the C standard library and is platform-specific.
  • It's mainly used for older DOS/Windows environments. Modern compilers may not support it.

<ctype.h> - Character Handling Functions

  • The ctype.h header file provides functions for character handling.
Example: Checking if a Character is a Digit
1#include <stdio.h>
2#include <ctype.h>
3
4int main() {
5    char ch = '7';
6    if (isdigit(ch)) {
7        printf("'%c' is a digit.\n", ch);
8    } else {
9        printf("'%c' is not a digit.\n", ch);
10    }
11    return 0;
12}
13
Explanation:
  • isdigit (ch): Checks if the character is a digit.

<math.h> - Mathematical Functions

  • The math.h header file provides mathematical functions.
Example: Calculating the Square Root
1#include <stdio.h>
2#include <math.h>
3
4int main() {
5    double number = 25.0;
6    double sqrt_result = sqrt(number);
7    printf("Square root of %lf is %lf\n", number, sqrt_result);
8    return 0;
9}
10
Explanation:
  • sqrt(number): Computes the square root of a number.

<string.h> - String Functions

  • The string.h header file provides functions for string manipulation.
Example: Concatenating Strings
1Example: Concatenating Strings
2#include <stdio.h>
3#include <string.h>
4
5int main() {
6    char str1[20] = "Hello, ";
7    char str2[] = "World!";
8    strcat(str1, str2); // Concatenate str2 to str1
9    printf("%s\n", str1);
10    return 0;
11}
12
Explanation:
  • strcat(str1, str2): Concatenates str2 to the end of str1.

Command Line Arguments

  • Command line arguments are parameters passed to a program when it's run in the terminal.
Example: Reading Command Line Arguments
1#include <stdio.h>
2
3int main(int argc, char *argv[]) {
4    if (argc < 2) {
5        printf("Usage: %s <your_argument>\n", argv[0]);
6        return 1;
7    }
8    printf("You provided: %s\n", argv[1]);
9    return 0;
10}
11

Conclusion

Now you have a basic understanding of some common standard library functions in C and how to use them, including working with command line arguments.