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c++getchar

How getchar() function output

I want to understand how is getchar() function is working here?

I read getchar() returns the next character from stdin, or EOF if the end of file is reached. 

#include <iostream>
#include <cstdio>
using namespace std;

int main() {
    int decimal;
    while(!isdigit(decimal=getchar()));
    cout<<decimal;
}

I give input 25. It outputs 50. I don't understand why? How is it giving 50.

Solution

  • getchar() reads a single character from the input stream and returns it's value. In your case, that is the character '2'. Most implementations (including yours it seems) use ASCII encoding where the character '2' has the value 50. The value assigned to decimal is therefore 50. Since decimal is an int, std::cout interprets it as a numeric value and prints it accordingly.