Introduction.
C is a powerful and flexible programming language, and its standard library provides a rich set of features, including input and output, string processing, mathematical calculations, and more, providing developers with powerful tools. This article will provide an in-depth look at the contents of the C standard library, including how to use them for input and output, string processing, and mathematical calculations, to help readers better grasp these important features.
1.Input-output functions.
The C standard library provides a range of input-output functions for reading data from a keyboard or file, as well as outputting data to a screen or file. Here are some commonly used input and output functions:
1.1.printf and scanf
The printf function is used to output formatted data to the screen. For example, printf("%d", num) can output the integer num to the screen.
The scanf function is used to read formatted data from the keyboard. For example, scanf("%d", &num) can read an integer from the keyboard and store it in the variable num.
1.2.File manipulation functions.
C also provides a set of file manipulation functions for reading and writing files. Common file manipulation functions include fopen, fclose, fread, and fwrite.
2.String handlers.
The C standard library provides a rich set of string handlers for handling character arrays (strings). Here are some commonly used string handlers:
2.1. `strlen`
The strlen function is used to calculate the length of a string, which is the number of characters in an array of characters. For example, strlen("hello") returns a value of 5.
2.2.strcpy and strncpy
The strcpy function is used to copy one string into another. For example, strcpy(dest, source) copies source into dest.
The strncpy function is used to copy a string of a specified length into the target string. For example, strncpy(dest, source, n) copies the first n characters from source into dest.
2.3.strcmp and strncmp
The strcmp function is used to compare whether two strings are equal. If equal, the return value is 0;If it is not equal, the return value is non-zero. For example, strcmp(str1, str2) compares whether str1 and str2 are equal.
The strncmp function is similar to strcmp, but only compares strings of a specified length.
2.4.strcat and strncat
The strcat function is used to append one string to the end of another. For example, strcat(dest, source) appends source to the end of dest.
The strncat function is similar to strcat, but only appends a string of the specified length.
3.Mathematical functions.
The C standard library also contains a series of mathematical functions for various mathematical calculations. Here are some commonly used math functions:
3.1. `sqrt`
The sqrt function is used to calculate the square root of a number. For example, sqrt(25.).0) returns a value of 50。
3.2. `pow`
The pow function is used to calculate the exponential power of a number. For example, pow(20, 3.0) The return value is 80。
3.3. `fabs`
The fabs function is used to calculate the absolute value of a number. For example, fabs(-3.).14) The return value is 314。
3.4.SIN and COS
The sin function is used to calculate the sinusoidal value of an angle.
The cos function is used to calculate the cosine value of an angle.
These numbers. Learning functions are very useful in scientific computing and engineering applications, where a variety of complex mathematical calculations can be performed.
4.How to use standard library functions.
To use C standard library functions, you need to include the appropriate header file and call the corresponding function. For example, to use the printf and scanf functions, you need to include a header file:
c#include
int main()
int num;
printf("Please enter an integer:");
scanf("%d", &num);
printf("The integer you entered is: %d", num);
return 0;
Similarly, to use a string handling function, you can include a header file and call the corresponding function. For example, to copy a string, you can use the strcpy function:
c#include
#include
int main()
char source = "hello, world!";
char dest[20];
strcpy(dest, source);
printf("Copied string: %s", dest);
return 0;
Math functions also need to contain appropriate header files, e.g. The relevant function can then be called directly.
5.Epilogue.
The C standard library provides a rich set of input/output, string processing, and mathematical calculation functions, providing a powerful tool for C developers. By gaining a deeper understanding of how to use these standard library functions, developers can write C programs more efficiently and handle a variety of complex calculations and data operations. It is hoped that the detailed explanations and examples provided in this article will help readers better understand the C language standard library and use these features flexibly in real projects. Whether it's console programming, embedded development, or scientific computing, the C standard library is an indispensable tool.