Hello forum, Vaironl here.

I was doing some very basic calculator program some weeks ago and someone told me to initialize my variables like

int x,y;
x = 0;
y = 0;


But I was wondering , if a value will be inputted later like 3 or 4 or whatever... Why do I have to say x = 0; or y = 0?

Thanks in advance

When you create a variable, without initializing it, it will be null. Here's an example:


int x;


x = null (nothing)


int x = 0;


x = 0

You can assign a value later in the code, but there's atleast two reasons (maybe more) to why you want to do it in the beginning.
1. Some compilers require that no variables are null.
2. It's easier to initilize all variables in one place, so you easy can go back later and change some values if you need to.

By always initializing variables, instead of assigning values to them before they are first used, the code is made more efficient since no temporary objects are created for the initialization. For objects having large amounts of data, this can result in significantly faster code.[/quote]

And the relevant wiki:

In computing, an uninitialized variable is a variable that is declared but is not set to a definite known value before it is used. It will have some value, but not a predictable one. As such it is a programming error and a common source of bugs in software.
A common assumption made by novice programmers is that variables are set to a known value, such as zero, when they are declared. While this is true for many languages, it is not true for all of them, and so the potential for error is there. Languages such as C use stack space for variables, and the collection of variables allocated for a subroutine is known as a stack frame. While the computer will set aside the appropriate amount of space for the stack frame, it usually does so simply by adjusting the value of the stack pointer, and does not set the memory itself to any new state. Therefore whatever contents of that memory at the time will appear as initial values of the variables which occupy those addresses.[/quote]

I had a bug recently in which I was using an uninitialized variable and the first operation I made with it was taking into account the value it already had. Too much confidence in oneself can lead to this kind of noob mistakes. That's why it's recommended to stick to good coding practices like initializing variables, just in case you were driving your programming locomotive like crazy and made a stupid mistake like that.

I never initialize variables at the point of definition and here is why: If you don't initialize it and you use it in a statement that consumes the variable value for example on the right sight of an assignment or in a funciton call as a non reference parameter, the compiler will give a big warning that you are using an uninitialized variable and will assert during run time. That is if you compile in debug mode and you are using Visual Studio. I don't know about other compilers but I would imagine they should have similar options