C programming

What Is a Variable in C?

Variables store different kind of data in the computer's memory, and take up a certain amount of space.

By storing information in a variable, you can retrieve and manipule it, perform various calculations, or even use it to make decisions in your program.
The stored data is given a name, and that is how you are able to access it when you need it.

How to Declare Variables in C

Before you can use a variable, you need to declare it – this step lets the compiler know that it should allocate some memory fo r it.
C is a strongly typed language, so to declare a variable in C, you first need to specify the type of data the variable will hold, such as an integer to store a whole number, a floating-point number for numbers with decimal places, or a char for a single character.
That way, during compilation time, the compiler knows if the variable is able to perform the actions it was set out to do.
Once you have specified the data type, you give the variable a name.
The general syntax for declaring variables looks something like this:data_type variable_name;

Let's take the following example:

                        #include <stdio.h>

                            int main(void) {
                            
                                int age;
                            }

In the example above, I declared a variable named age that will hold integer values.

What Are the Naming Conventions for Variables in C?

When it comes to variable names, they must begin either with a letter or an underscore.
For example, age and _age are valid variable names. Also, they can contain any uppercase or lowercase letters, numbers, or an underscore character. There can be no other special symbols besides an underscore.
Lastly, variable names are case-sensitive. For example, age is different from Age.

How to Initialize Variables in C

Once you've declared a variable, it is a good practice to intialize it, which involves assigning an initial value to the variable.
The general syntax for initialzing a variable looks like this:data_type variable_name = value;
The assignment operator, =, is used to assign the value to the variable_name. Let's take the previous example and assign age a value:

                        #include <stdio.h>

                            int main(void) {
                                    
                            int age;
                                    
                            age = 29;
                            }

I initialized the variable age by assigning it an integer value of 29. With that said, you can combine the initialization and declaration steps instead of performing them separately:

                            #include <stdio.h>

                                int main(void) {
                                    
                                // declaration + initialization
                               int age = 29;
                                    }

How to Update Variable Values in C

The values of variables can change.
For example, you can change the value of age without having to specify its type again.
Here is how you would change its value from 29 to 30:

                            #include <stdio.h>  

                                int main(void) {
                                                
                                // the variable age with its original value
                                int age = 29;
                                                
                                // changing the value of age
                                // the new value will be 30
                                age = 30;
                                }

Note that the data type of the new value being assigned must match the declared data type of the variable.
If it doesn't, the program will not run as expected. The compiler will raise an error during compilation time.

                            #include <stdio.h>

                                int main(void) {
                                            
                                int age = 29;
                                /*
                                trying to assign a floating-point value
                                to a variable with type int
                                will cause an error in your program
                                */
                                age = 29.5;
                            }

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Test Your Knowledge

Choose The

With supporting text below as a natural lead-in to additional content.

Q1. A variable name can have ?

A. Any special symbol

B. Blank space

C. Comma ( , )

D. Underscore

Q2. Which pair of symbols is used to define the scope of functions, loops, and other code blocks in C?

A. ( )

B. { }

C. [ ]

D. < >