Solve programming problems: comprehensively master the C language function library

Master the complete collection of C language function libraries and easily solve programming problems. Specific code examples are needed

In C language programming, we often need to use various function libraries to solve problems Specific programming questions. A function library is a collection of pre-written functions. By calling these functions, we can implement various functions, making our programming process more efficient and convenient.

Below I will introduce some commonly used C language function libraries and specific code examples.

1. stdio.h: This function library provides standard input and output functions, such as printf and scanf. Through the printf function, we can print data to the screen, and the scanf function can obtain user-entered data from the keyboard. The following is a sample code using the stdio.h function library:

#include <stdio.h>

int main() {
   int num;
   printf("请输入一个整数：");
   scanf("%d", &num);
   printf("你输入的整数是：%d
", num);
   return 0;
}

2. math.h: This function library contains various mathematical functions, such as the commonly used square root function sqrt and power function pow, trigonometric functions sin, cos, etc. The following is a sample code using the math.h function library:

#include <stdio.h>
#include <math.h>

int main() {
   double num = 16.0;
   printf("16的平方根是：%lf
", sqrt(num));
   printf("2的5次方是：%lf
", pow(2, 5));
   printf("90度的正弦值是：%lf
", sin(90));
   printf("60度的余弦值是：%lf
", cos(60));
   return 0;
}

3. string.h: This function library provides string processing functions, such as the string copy function strcpy and string concatenation. Function strcat, string comparison function strcmp, etc. The following is a sample code using the string.h function library:

#include <stdio.h>
#include <string.h>

int main() {
   char str1[20] = "Hello";
   char str2[20] = "World";
   strcat(str1, str2);
   printf("字符串连接后的结果是：%s
", str1);
   
   if(strcmp(str1, str2) == 0) {
      printf("两个字符串相等
");
   } else {
      printf("两个字符串不相等
");
   }
   return 0;
}

4. time.h: This function library provides time and date related functions, such as the function time to obtain the current time, Functions such as strftime that format times into strings. The following is a sample code using the time.h function library:

#include <stdio.h>
#include <time.h>

int main() {
   time_t t = time(NULL);
   char buffer[80];
   struct tm* timeinfo = localtime(&t);
   strftime(buffer, 80, "当前时间是：%Y-%m-%d %H:%M:%S", timeinfo);
   printf("%s
", buffer);
   return 0;
}

In addition to the function libraries introduced above, there are many other commonly used function libraries, such as stdlib.h, ctype.h, stdarg. h and so on, they provide a variety of functions to meet different programming needs.

Mastering the C language function library can provide more concise and efficient solutions to various problems we encounter in the programming process. Through continuous learning and practice, we can master these function libraries and flexibly apply them in actual projects. I hope the above code examples can help everyone better understand and use these function libraries. By continuously accumulating experience, we can become more professional and efficient in programming, and easily solve various programming problems.

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