Variables

Learn how to create, set and read variables (changable values) in C

Base code

For every C program, we need to define the main function. We’ll start off this chapter from this code:

int main(int argc, char* argv[]) {
    // we'll write our new code here
    return 0;
}

Declaring a variable

Variable declaration is where we create a variable. We don’t necessarily give it a value yet - that’s assignment.

The syntax in C for declaring a variable is:

type variableName;

There are various different data types we can use - they will all be discussed in a later chapter! One of them is the int, for a signed integer. We can declare an integer variable called, for example, numPages like this:

int numPages;

If we try to access a variable that has been declared but not initialised or assigned, then we may get garbage data.

Assigning a variable

Once we’ve declared a variable, we can give it a value through assignment.

For example, take the numPages example from above. We can give numPages a value of 382 using this code:

int numPages;
numPages = 382;

We can also assign a variable even after it has already been assigned before, because the variable is mutable:

int numPages;
numPages = 382;
// do something with numPages
numPages = 395; // maybe the author added some pages?