Variables in C Programming

A variable is a name given to a memory location inside our computer where we can store data.

Variable declaration
int age;
In C programming, a variable declaration is a statement that informs the compiler about the name and type of a variable without allocating any memory for it. It essentially tells the compiler that a variable with a specific name and data type will be used in the program. Variable declarations are necessary before you can use a variable in your program.

Variable Initialisation
age = 22
Variable initialisation in C refers to the process of assigning an initial value to a variable when it is declared.

We can write variable declaration and initialisation in single line: int age = 22;

Changing values in variable

#include <stdio.h>

int main(){
    int age = 25;
    printf("Age: %d", age);

    age = 31;
    printf("\nNew AGE: %d", age); 

    return 0;
}

• %d is format specifier. It is a special character sequence used in the printf and scanf functions (and related functions) to specify the type and format of the data that will be input or output.

• \n is used for new line.

Assigning one variable to another variable

#include <stdio.h>

int main(){

    int firstNumber = 33;
    printf("firstNumber = %d", firstNumber);

    int secondNumber = firstNumber;
    printf("\nsecondNumber = %d", secondNumber);

    return 0;
}

Declaring two variable in a single line

#include <stdio.h>

int main(){

    int variable1, variable2=25;

    return 0;
}

Variable naming convention

• Use camel case variable like myAge, firstName, lightSpeed. Cannot:
  • Create variable names with space in between. int first number
  • Start variable names with numbers. int 1number
  • Use keywords as variables. int if