Q:

Decimal string to char

Is there a way to convert numeric string to a char containing that value? For example, the string "128" should convert to a char holding the value 128.

A:

Yes... atoi from C.
char mychar = (char)atoi("128");

A more C++ oriented approach would be...
template<class T>
    T fromString(const std::string& s)
{
     std::istringstream stream (s);
     T t;
     stream >> t;
     return t;
}

char mychar = (char)fromString<int>(mycppstring);

A:

There's the C-style atoi, but it converts to an int. You 'll have to cast to char yourself.
For a C++ style solution (which is also safer) you can do
string input("128");
stringstream ss(str);
int num;
if((ss >> num).fail()) { 
    // invalid format or other error
}

char result = (char)num;

