c语言字符转数字函数(c语言怎么将字符转成数字)

1. Introduction

C language provides several built-in functions that allow the conversion of characters to integers. These functions play a crucial role in various programming scenarios, especially when dealing with user input or when working with strings. In this article, we will explore three important character to number conversion functions in C: atoi(), atof(), and sscanf(). We will discuss their usage, differences, and common scenarios where they are applicable.

2. The atoi() Function

The atoi() function in C converts a string of numeric characters to an integer. It takes a string as input and returns the equivalent integer value. Here's the syntax:

int atoi(const char *str);

Here, str is the input string that needs to be converted into an integer. The atoi() function parses the string from left to right and stops when it encounters a non-numeric character or the end of the string. It returns the integer corresponding to the parsed characters.

For example:

char str[] = "1234";
int num = atoi(str);

In this case, the atoi() function will convert the string "1234" to the integer value 1234.

3. The atof() and sscanf() Functions

Both atof() and sscanf() functions in C are used to convert a string to a floating-point number.

The atof() function takes a string as input and returns the equivalent floating-point number. Here's the syntax:

double atof(const char *str);

Similar to atoi(), atof() also parses the string from left to right. It stops when it encounters a non-numeric character or the end of the string. It returns the floating-point number corresponding to the parsed characters.

For example:

char str[] = "3.14";
double num = atof(str);

In this case, the atof() function will convert the string "3.14" to the floating-point number 3.14.

The sscanf() function in C allows formatted input parsing. It can be used to read values from a string and store them in variables. The following example shows the usage of sscanf() to convert a string to a floating-point number:

char str[] = "5.67";
double num;
sscanf(str, "%lf", &num);

In this case, the sscanf() function reads the value from "5.67" and stores it in the variable 'num' as a floating-point number.

Conclusion

In conclusion, C provides several functions for converting characters to numbers. atoi(), atof(), and sscanf() are widely used in C programming. The atoi() function converts a string to an integer, while atof() and sscanf() are used for converting strings to floating-point numbers. It's important to note that these conversion functions handle parsing differently and stop when encountering a non-numeric character or the end of the string. Understanding the differences and appropriate usage of these functions will greatly enhance your ability to work with character to number conversions in C programming.