C++ 字元處理函式（cctype標頭檔案）

函式	說明
int isupper(char)	判斷字元是否是大寫字母
int islower(char)	判斷字元是否是小寫字母
int isalpha(char)	判斷字元是否是字母
int isdigit(char)	判斷字元是否是數字
int isalnum(char)	判斷字元是否是字母或數字
int isspace(char)	判斷字元是否是空白
int isblank(char)	判斷字元是否是空格
int ispunct(char)	判斷字元是否是標點符號
int isprint(char)	判斷字元能否列印
int iscntrl(char)	判斷字元是否是控制字元
int isgraph(char)	判斷字元是否是圖形字元
int tolower(char)	將字元轉換為小寫
int toupper(char)	將字元轉換為大寫

#include <iostream>
#include "cctype"

int main() {
    using std::cout;
    char c{'A'};
    cout << "A isupper:" << (isupper(c) ? "true" : "false") << char(10); 
    cout << "A islower:" << (islower(c) ? "true" : "false") << char(10);
    cout << "A isalpha:" << (isalpha(c) ? "true" : "false") << char(10);
    cout << "A isdigit:" << (isdigit(c) ? "true" : "false") << char(10);
    cout << "A isalnum:" << (isalnum(c) ? "true" : "false") << char(10);
    cout << "A isblank:" << (isblank(c) ? "true" : "false") << char(10);
    cout << "A isalnum:" << (isalnum(c) ? "true" : "false") << char(10);
    cout << "A ispunct:" << (ispunct(c) ? "true" : "false") << char(10);
    cout << "A isprint:" << (isprint(c) ? "true" : "false") << char(10);
    cout << "A iscntrl:" << (iscntrl(c) ? "true" : "false") << char(10);
    cout << "A isgraph:" << (isgraph(c) ? "true" : "false") << char(10);
    cout << "A tolower:" << char(tolower(c)) << char(10);
    cout << "A toupper:" << char(toupper(c)) << char(10);
    return 0;
}

A isupper:true
A islower:false
A isalpha:true
A isdigit:false
A isalnum:true
A isblank:false
A isalnum:true
A ispunct:false
A isprint:true
A iscntrl:false
A isgraph:true
A tolower:a
A toupper:A