Determine the type of characters being input in the C language.

1 year ago
Jackson Davis
2 minutes

In C programming language, you can use functions from the header file ctype.h to determine the type of input characters. Here are some commonly used functions:

  1. Is the character alphanumeric?
  2. Does the character c belong to the alphabet?
  3. Does the character c consist of only digits?
  4. Is the character c lowercase?
  5. does c contain only uppercase letters
  6. Is the character c a white space character?
  7. Is the character c a punctuation mark?
  8. The character c is a hexadecimal digit.

The return value of these functions being non-zero (true) indicates that the character meets the type condition, while a return value of zero (false) indicates that the character does not meet the type condition.

Here is a sample program that determines the type of character input by the user.

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

int main() {
    char c;

    printf("请输入一个字符：");
    scanf("%c", &c);

    if (isalnum(c)) {
        printf("输入的字符是字母或数字\n");
    } else if (isalpha(c)) {
        printf("输入的字符是字母\n");
    } else if (isdigit(c)) {
        printf("输入的字符是数字\n");
    } else if (islower(c)) {
        printf("输入的字符是小写字母\n");
    } else if (isupper(c)) {
        printf("输入的字符是大写字母\n");
    } else if (isspace(c)) {
        printf("输入的字符是空白字符\n");
    } else if (ispunct(c)) {
        printf("输入的字符是标点符号\n");
    } else if (isxdigit(c)) {
        printf("输入的字符是十六进制数字\n");
    } else {
        printf("输入的字符无法识别\n");
    }

    return 0;
}

After running the program, the user can input a character, and the program will determine and output the type of that character.

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