Variables are made by programmers.It can be modified.When we defined any data object as a singular variable can be defined also as an array. In C variable are of many type. Like: an integer or character, or may be of compound data objects(Like: structure or unions). Initialization of variable: int num; //Here we declare num variable as integer and it is initialized as default size. int num=0; //Here we declare num variable and initialize them with 0.