How to convert characters to numbers in the C language?

In C language, there are several ways to convert characters to numbers:

1. Converts a string to an integer.
2. Include the standard library header file .

#include <stdio.h>
#include <stdlib.h>

int main() {
    char c = '5';
    int num = atoi(&c);
    printf("%d\n", num);  // 输出：5
    
    return 0;
}

1. “Read input from string”
2. The header file stdio.h.

#include <stdio.h>

int main() {
    char c = '7';
    int num;
    sscanf(&c, "%d", &num);
    printf("%d\n", num);  // 输出：7
    
    return 0;
}

1. Converting with ASCII values: Subtracting the ASCII value of the character ‘0’ from the ASCII value of the character itself will give you the corresponding number.

#include <stdio.h>

int main() {
    char c = '9';
    int num = c - '0';
    printf("%d\n", num);  // 输出：9
    
    return 0;
}

The methods above are commonly used for converting characters to numbers, and the specific method used depends on the actual requirements and personal preferences.