isalnum

1isalpha() - To check Alphabets
2isnumeric() - To check Number
3isalnum() - To check both alphabates and number

1string test = "Ab4 :";
2std::isalnum(test[0]);	//true
3std::isalnum(test[1]);	//true
4std::isalnum(test[2]);	//true
5std::isalnum(test[3]);	//false
6std::isalnum(test[4]);	//false