I am curious how this works to produce the provided output. The output is 4 which is the 5th character in the alphabet (which is expected) and subsequent alphabetical characters work all the way to the z character which also returns 25.
Example program
#include <iostream> #include <string> using namespace std; int main() { string str = "e"; int numericalvalue = ((str[0]) - 'a'); //this line of code im trying to understand cout << numericalvalue; return 0; } It has to do with the ASCII table.
Its character in the set is assigned a unique integer. In your case, the literal 'a' has the value of 97 in the ASCII table and the character e has the value of 101. By subtracting 101 - 97 = 4 you get the final result.
More on the ASCII table can be found here
char is an integral type, so it's implicitly convertible (specifically, it undergoes integral promotion) to type int. Each character that you can represent with a basic char has a numeric value from 0-255 (or -128 to 127). So saying 'a' - '0' is actually valid since it's exactly like saying 97 - 48 with ints.
The character 'a' has the ASCII decimal value 97.
Letters after 'a' have a decimal value greater 97.
The substraction
str[0] - 'a' uses the ASCII decimal values which produces the letters position in the alphabet.
char e = 'e'; char a = 'a'; std::cout << "e = " << static_cast<int>(e) << std::endl; std::cout << "a = " << static_cast<int>(a) << std::endl; computers don't have such abstract things like "characters". They only work with 1's and 0's.. (numbers). The computer works with a number but knows, once it get's printed out on the screen, use the graphic that's in a .ttf file that represents that "character".
