Question: how to do isdigit in c++?
Answer: int isdigit(int ch); The isdigit() function checks if ch is a digit or not i.e one of 0,1,2,3,4,5,6,7,8 and 9. The behaviour of isdigit() is undefined if the value of ch is not representable as unsigned char or is not equal to EOF. It is defined in <cctype> header file.