What do these lines of code mean?

[Wulfinite]

Question says it all.

 //Number 1:
int length;
length = (int)input.length();

//Number 2:
isalpha(input[count])

[MiiNiPaa]

1) c-style cast: http://en.cppreference.com/w/cpp/language/explicit_cast
2) Check if character is alphabet character http://en.cppreference.com/w/cpp/string/byte/isalpha

[Wulfinite]

And how bout this part:


(input[count])

[AbstractionAnon]

You didn't show the definition of input, but presumably it is a std::string.
input[n] returns the n'th character of the string.
http://www.cplusplus.com/reference/string/string/operator[]/

[MiiNiPaa]

http://www.cplusplus.com/doc/tutorial/arrays/