Add two integers

In the following program, we will ask the user to enter two integer inputs. The programs will calculate and print the sum of two numbers.

C

src/c/basics/01-add-two-integers.c

#include <stdio.h>

int main()
{
    int input1, input2, sum;

    printf("Enter input 1: ");
    scanf("%d", &input1);

    printf("Enter input 2: ");
    scanf("%d", &input2);

    sum = input1 + input2;

    printf("%d + %d = %d\n", input1, input2, sum);

    return 0;
}

C++

src/cpp/basics/01-add-two-integers.cpp

#include <iostream>
using namespace std;
// above declaration exposes all the methods described in the std namespace
// so that we can use cout instead of std::cout. Beware that in large
// applications there could be naming conflict among various imported headers.
// We can either use the convention std::cout or declare only the methods we
// need:
// using std::cout;

int main()
{
    int input1, input2, sum;

    cout << "Enter input 1: ";
    cin >> input1;

    cout << "Enter input 2: ";
    cin >> input2;

    sum = input1 + input2;

    cout << input1 << " + " << input2 << " = " << sum << endl;

    return 0;
}

danger

int a = 123456789;
long long b = a * a; // this is wrong, a * a will result in int type
long long c = (long long) a * a; // or change the type of a to long long

caution

It is risky to compare floating point numbers with == due to precision errors. Better approach is to check the difference is less than a small number:

if (abs(a - b) < 1e-9)
{
    // a and b are equal
}