How many letters are there in a string of characters in C language?

To determine the number of letters in a string of characters, you can use the character processing function isalpha() in C language.

The isalpha() function is used to determine whether a character is a letter. It returns a non-zero value if it is a letter, otherwise it returns 0.

Here is an example code to count the number of letters in a string:

#include <stdio.h>
#include <ctype.h>

int main() {
    char str[100];
    int count = 0;

    printf("请输入一串字符：");
    scanf("%s", str);

    for (int i = 0; str[i] != '\0'; i++) {
        if (isalpha(str[i])) {
            count++;
        }
    }

    printf("字符串中的字母个数为：%d\n", count);

    return 0;
}

After running the program, input a string of characters and the program will calculate the number of letters in it and display the result.