01. What are token? What are different types of tokens used in C++?
Tokens are the basic building blocks of a C++ program. There are five types of tokens in C++.
1. Key words: Key words are tokens that carry a specific meaning to the language compiler.
Eg. int, switch etc..
2. Identifiers: Identifiers are user defined words that are used to name different program elements
such as memory locations, statements, functions, classes etc.
Identifiers used for naming memory location is known as variables.
Identifiers assigned to statements are known as labels.
Identifiers used for set of statements are known as functions.
3. Literal : Literals are data items that never change their values during the program running. They
are also known as constants. There are 4 types of literals
a) Integer literal: tokens formed only by digits. It must have at least one digit and must
not have decimal point. It may contain +ve or _ve sign as first character
Eg. 15, -20, +40
b) Floating Point Literal (Real constants): They have fractional part. They can be
written in two forms: Fractional and exponential form.
They have at least one digit and a decimal point. They have either +ve or –ve sign.
In exponential form, there are two parts, Mantissa (Parts appearing before E) and
Exponential(Power).
Eg: 52.15, -715.12, .458E04
c) Character Literal : Single character enclosed with single quotes and that never
changes its value during program run. Non graphical symbols can be represented by
using escape sequence which consists of a back slash(\) followed by one or more
characters. (eg. \n, \a)
Eg. Valid Character Literal: ‘s’, ‘$’,’\n’
Invalid Character Literal: ‘82’, “k”, ‘\8’
d). String Literals: Sequence of one or more characters enclosed within a pair of
double quotes.
Eg. “computer”. Every string in C++ terminated by a null (\o) character.
4. Punctuators: Special symbols that have syntactic or semantic meaning to the compiler.
Eg: #, : , ’ , ” ,() ,[]
