Complete C language function library: an essential tool to improve programming efficiency

C language function library collection: a tool that makes programming more efficient

Overview:
C language, as a low-level language, is efficient, flexible, and cross-platform and other characteristics, it is widely used in system programming, embedded development, network communications and other fields. As an important programming tool, the C language function library can provide rich functions and commonly used algorithms, which greatly simplifies the difficulty of program development and code maintenance. This article will introduce some commonly used C language function libraries and give specific code examples to help readers better understand and apply these function libraries.

I. Standard function library

1. : This library contains input and output functions, such as printf() and scanf(). By using these functions, you can easily perform screen input and output operations.

Sample code:

#include <stdio.h>
int main() {
    int num;
    printf("Enter a number: ");
    scanf("%d", &num);
    printf("The number is: %d
", num);
    return 0;
}

2. : This library provides some commonly used functions, such as memory allocation functions: malloc(), free() , Random number generation functions: rand(), srand(), etc.

Sample code:

#include <stdlib.h>
#include <stdio.h>
int main() {
    int* arr = malloc(5 * sizeof(int));
    if (arr == NULL) {
        printf("Memory allocation failed.
");
        return 1;
    }
    for (int i = 0; i < 5; i++) {
        arr[i] = rand() % 100;
        printf("Random number %d: %d
", i+1, arr[i]);
    }
    free(arr);
    return 0;
}

II. Mathematical function library

1. : This library provides mathematical functions, such as trigonometric functions : sin(), cos(), tan(), data rounding functions: round(), floor(), ceil(), etc.

Sample code:

#include <math.h>
#include <stdio.h>
int main() {
    double angle = 30;
    double radian = angle * M_PI / 180;
    double sinValue = sin(radian);
    double cosValue = cos(radian);
    double tanValue = tan(radian);
    printf("sin(30°) = %.3f
", sinValue);
    printf("cos(30°) = %.3f
", cosValue);
    printf("tan(30°) = %.3f
", tanValue);
    return 0;
}

III. String processing function library

1. : This library provides functions for string processing Operation functions, such as string copy functions: strcpy(), strncpy(), string connection functions: strcat(), strncat(), etc.

Sample code:

#include <stdio.h>
#include <string.h>
int main() {
    char str1[20] = "Hello";
    char str2[] = "World";
    strcat(str1, str2);
    printf("Concatenated string: %s
", str1);
    return 0;
}

IV. Time and date function library

1. : This library provides access to time and date Functions, such as the function to obtain the current time: time(), the function to format time output: ctime(), the function to obtain the clock time: clock(), etc.

Sample code:

#include <stdio.h>
#include <time.h>
int main() {
    time_t currentTime;
    struct tm *localTime;
    currentTime = time(NULL);
    localTime = localtime(&currentTime);
    printf("Current date and time: %s
", ctime(&currentTime));
    printf("Current year: %d
", localTime->tm_year + 1900);
    printf("Current month: %d
", localTime->tm_mon + 1);
    printf("Current day: %d
", localTime->tm_mday);
    return 0;
}

Summary:
This article introduces some commonly used C language function libraries, including standard function library, mathematical function library, string processing function library and Time and date function library, and specific code examples are given. These function libraries can greatly simplify the program development process and improve the readability and maintainability of the code. Readers can flexibly use these function libraries according to their own needs to make programming more efficient and improve program performance and quality.

The above is the detailed content of Complete C language function library: an essential tool to improve programming efficiency. For more information, please follow other related articles on the PHP Chinese website!