ILIA_93's Helping Center

Short answer
You should use int H1=0;

Long answer
If you want to use a variable H1, you need to tell the compiler to "reserve" some space in memory that you will refer to as "H1".

Where should it be? Anywhere in the memory (the RAM) of your computer. It's your OS (Windows) who will decide.

How big should it be? It depends on the type of the variable you want to use.

You write int H1. So you ask for a space in memory of the size equivalent to int. Depending on your system that usually means 4 or 8 bytes. You can know the size on your system with the following code:

printf("%d\n", sizeof(int));

When you declare a variable, here's what happens:

C program - read "int H1"
C program - ask Windows: "Give me 4/8 bytes of memory"
Windows - replies to Cprogram : "Here's one. It starts at address 0x04f56bc8"
C program "Every time I read the variable H1, I will look for address 0x04f56bc8"

It is important that you understand that.

However there is a problem. We don't know what is written at address 0x04f56bc8. A previous program may have written anything, maybe malicious code.

This is why in C, the first thing you do when you declare a variable is to initialize it. That means write over the address 0x04f56bc8 with something we know is good.

In your case you want to initialize with a "neutral" integer. The common usage is to use 0. But it can be any variable you chose. For example:

int main()
{
    int a=100; // I initialized variable a to 100
    printf("%d", a);
}