How to make a condition in string data type that a user is not allowed to input numbers? Also how to set a limit on it?

Question

example:
sample run 1:
enter your first name: khaizer

sample run 2:
enter your first name: 851565415684188515
Invalid input! please try again.
enter your first name:

sample run 3:
enter your first name: dssjxsbfwjdbkndkjdbdjd
Invalid input! 15 character only! please try again.
enter your first name:

Answer 1

bool CheckLength(char * Input, int MaxLength)
{
if (strlen(Input) > MaxLength) { return false; }
else { return true; }
}

bool IsAllLetters(char * Input)
{
int len = strlen(Input);
for (int i = 0; i < len; i++)
{
if (((Input[i] >= 'a') && (Input[i] <= 'z')) ||
((Input[i] >= 'A') && (Input[i] <= 'Z')))
{
return false;
}
}
return true;
}

void main()
{
string Name;
while (true)
{
cin >> Name;
if (CheckLength(Name, 15))
cout << "Length error ....";
else if (IsAllLetters(Name))
cout << "Not a name..";
else
break;
}
}