Class Notes :Chapter 1
I. 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: #, : , ’ , ” ,() ,[]
Prepared by Anil Kumar, Govt HSS ,Kuzhumathikkad, Kollam [HSSLiVE.IN]2
5. Operators: Operators are the tokens that trigger some kind of operations. The operations applied
on a set of data called operands.
Based on the number of operands, operators are classified into three, Unary operator, Binary
operator and Ternary operator.
A unary operator acts on a single operand. A binary operator acts on two operands. A ternary
operator(? :) acts on three operands.
Based on the nature of operation operators are classified into three Arithmetic, Relational and
Logical operator.
a). Arithmetic operator are used for addition, subtraction, multiplication and division(+, - , * , / ).
C++ provides a special operator modulus operator(%) for getting remainder of division operation.
For example 10 % 2 returns 0.
b) Relational operators
Relational operators are used to compare values. They produces only ‘True’ of ‘False’ values.
The following are the relational operators in C++.
c). Logical operator
Logical operators allows us to combine two or more conditions. They are often referred to as
Boolean operators. The logical operators are &&(logical AND),||(logical OR),and !(logical NOT).
There are some other operators such as,
d). Input-Output operators
The Input-Output operators are used to take input and display output. The operator(>>) is used
for taking input, and the operator(<<) is used to display the output. The >> operator is called
extraction or get from operator. The operator << is called insertion or put to operator. These are
binary operators.
The input operator is used with standard input stream, cin and the output operator is used with
standard output stream, cout. The input operator takes the value through cin and stores in a variable.
cin >> number;
cout << number+2;
Cascading of I/O operators
The multiple use of input or output operators in a single statement is called cascading of I/O
operators.
Eg. cin>>a>>b;
e). Assignment operator (=)
The assignment operator is used to assign a value to a variable.
For example a=10 Assigns the value 10 to a
The symbol = assigns a value, where as the symbol == compare two values(Relational Operator).
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: #, : , ’ , ” ,() ,[]
Prepared by Anil Kumar, Govt HSS ,Kuzhumathikkad, Kollam [HSSLiVE.IN]2
5. Operators: Operators are the tokens that trigger some kind of operations. The operations applied
on a set of data called operands.
Based on the number of operands, operators are classified into three, Unary operator, Binary
operator and Ternary operator.
A unary operator acts on a single operand. A binary operator acts on two operands. A ternary
operator(? :) acts on three operands.
Based on the nature of operation operators are classified into three Arithmetic, Relational and
Logical operator.
a). Arithmetic operator are used for addition, subtraction, multiplication and division(+, - , * , / ).
C++ provides a special operator modulus operator(%) for getting remainder of division operation.
For example 10 % 2 returns 0.
b) Relational operators
Relational operators are used to compare values. They produces only ‘True’ of ‘False’ values.
The following are the relational operators in C++.
c). Logical operator
Logical operators allows us to combine two or more conditions. They are often referred to as
Boolean operators. The logical operators are &&(logical AND),||(logical OR),and !(logical NOT).
There are some other operators such as,
d). Input-Output operators
The Input-Output operators are used to take input and display output. The operator(>>) is used
for taking input, and the operator(<<) is used to display the output. The >> operator is called
extraction or get from operator. The operator << is called insertion or put to operator. These are
binary operators.
The input operator is used with standard input stream, cin and the output operator is used with
standard output stream, cout. The input operator takes the value through cin and stores in a variable.
cin >> number;
cout << number+2;
Cascading of I/O operators
The multiple use of input or output operators in a single statement is called cascading of I/O
operators.
Eg. cin>>a>>b;
e). Assignment operator (=)
The assignment operator is used to assign a value to a variable.
For example a=10 Assigns the value 10 to a
The symbol = assigns a value, where as the symbol == compare two values(Relational Operator).
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