In short What is Variable in Arduino

• A variable is a named unit of data that may be assigned a value.
• variable is a named location in a memory where a program can manipulate the data. This location is used to hold the value of the variable.
• The value of the C variable may get change in the program.
• variable might be belonging to any of the data type like int, float, char etc.

RULES FOR NAMING VARIABLE

• Variable name must begin with letter.
• Variables are case sensitive
• They can be constructed with digits, letters.
• No special symbols are allowed other than underscore.
• sum, height ,name ,age are some examples for variable name

Example :

int led=5;

(int data type led is defined as 5 ) in entire program led is know for its value 5.

int age= 26;

(int data type age is defined as 26 ) in entire program age is know for its value 26.

age=age+2;

now age has 28 in its value. but age is name of variable in memory until program execution.

See Video Lecture