1. Character set: 

To study a language first we have to familiarize the character set. For example, to study English language first we have to study the alphabets. Similarly here the character set includes letters(A to Z & a to z), digits(0 to 9), special characters(+, -, ?, *, /, …..) white spaces(non printable), etc.

2. Token: It is the smallest individual units similar to a word in English or Malayalam language. C++ has 5 tokens 

• Keywords: These are reserved words for the compiler. We can’t use for any other purposes. 

Eg: float is used to declare variable to store numbers with decimal point. We can’t use this for any other purpose

• Identifier: These are user defined words. 

Eg: variable name, function name, class name, object name, etc… 

• Literals (Constants): Its value does not change during execution 

eg: In maths % = 3.14157 and boiling point of water is 100. 

• Punctuators: In English or Malayalam language punctuation mark are used to increase the readability but here it is used to separate the tokens. 

eg:{,}, (,), …….. 

• Operators: These are symbols used to perform an operation(Arithmetic, relational, logical, etc…).