c++ - Initialize a variable

Question

Is it better to declare and initialize the variable or just declare it? What's the best and the most efficient way?

For example, I have this code:

#include <stdio.h>

int main()
{
    int number = 0;

    printf("Enter with a number: ");
    scanf("%d", &number);

    if(number < 0)
        number= -number;

    printf("The modulo is: %d
", number);

    return 0;
}

If I don't initialize number, the code works fine, but I want to know, is it faster, better, more efficient? Is it good to initialize the variable?

Answer 1

scanf can fail, in which case nothing is written to number. So if you want your code to be correct you need to initialize it (or check the return value of scanf).

The speed of incorrect code is usually irrelevant, but for you example code if there is a difference in speed at all then I doubt you would ever be able to measure it. Setting an int to 0 is much faster than I/O.