High and low level programming languages. Basics of programming languages

data.
To indicate the storage area, each variable should be given a unique name (identifier). Variable names are just the symbolic representation of a memory location. For example:

Here, playerScore is a variable of integer type. The variable is assigned value: 95.
The value of a variable can be changed, hence the name 'variable'.
In C programming, you have to declare a variable before you can use it.

int playerScore = 95;

letters (both uppercase and lowercase letters), digits and underscore only.
The first letter of a variable should be either a letter or an underscore. However, it is discouraged to start variable name with an underscore. It is because variable name that starts with an underscore can conflict with system name and may cause error.
There is no rule on how long a variable can be. However, only the first 31 characters of a variable are checked by the compiler. So, the first 31 letters of two variables in a program should be different.
C is a strongly typed language. What this means it that, the type of a variable cannot be changed.

be altered in a program. For example: 1, 2.5, "C programming is easy", etc.
As mentioned, an identifier also can be defined as a constant.
const double PI = 3.14

Constants

here, PI is a constant. Basically what it means is that, PI and 3.14 is same for this program.
Below are the different types of constants you can use in C.