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Identifier
The identifiers are the names used torepresent variable ,constants, types
functions in the program
Types of identifiers
Standard identifiers
User defined identifiers
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Standard identifier
A type of identifier that has the special meaning
in the c++
cout and cin are example of standard identifiers
User-defined IdentifierThe type of Identifier that is defined by the
Programmer to access memory location known
as user-defined Identifier.
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The user-defined identifiers are used to store
data and program results.
Some examples of user-defined identifiers are,
marks and age etc.
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Keywords
Keywords is a word in C++ language that has a
predefined and purpose.
The meaning and purpose of a keyword is
defined by the developer of the language.
It can not be changed or redefined by user.
Keyword can be used for the same purpose for
which it is defined.
Keyword can be used for the same purpose for
which it is defined.
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Keywords are also known as reserved words.
These are different types of keywords in C++
language.
The total number of keywords is 63.
Char, do, If struct float
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Data types
Data type defines a set of values and a set of operations
of those values
The data is given to the program as input
The data is processed according to the program
instruction and output is returned
A C++ program may need to process different types of
data
Each data type require different amount of memory
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Types of data type
Integer data typeFloat data type
Double data type
Char data type
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Integer data type
A numeric value that has no decimal point or fraction
It includes both positive and negative valueTypes of integers
C++ provides different types of integer data
Int
Short intLong int
Unsigned int
Unsigned long int
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Int data type
Is used to store integer values
It takes two or four bytes in memoryIt takes two bytes and its range is from -32768 to 32767
Unsigned int data type
Is used to store the positive integer values
It takes two bytes in memoryIts range is from 0 to 65,535
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Unsigned long integer data type
Is used to store positive integer values
It takes four bytes in memory its range is from 0 to4,294967295
Long integer data type
Long integer data type is used to store large integer
valueIt takes 4 bytes in memory
Its range is from2,147,483648 to 2,147,483,647
Short int data type
Is used to store integer value
It takes two bytes in memory
Its range is from o to 65,535
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Real data type
Real data type is numeric value with decimal point or
fraction
It is also called floating point number
It includes both positive number and negative number
Example are 10.5,-10.91
Types
Float
Long float
Double
long double
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Float data type
Float data type is used to store real values
It takes four bytes in memoryIts range is from 3.4*1038 to 3.4*10-38
Double data type
Double data type is used to store large real values
It takes 8 bytes in memory
Its range is from 1.7*10-308 to 1.7*10308
It provides accuracy of 15 decimal places
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Long double data type
Long double data type is used to store very large
real values
It takes 10 bytes in memory
its range is from 1.7*10-4932 to 1.7*10 4932
it provides accuracy of 19 decimal places
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Character data type
Char data type is used to store char value
It takes one byte in memoryIt is used to represent a letter, number, or punctuation mark and a
few other symbols
Character values is normally given in single quotes
It can represent individually characters such as a,x,5
Character 5 is treated differently than integer 5
The key word signed and unsigned can be used char data type
The signed character can represent number from 127 to -128
The unsigned characters can represent number from 0 to 255
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Integer over flow and under flow
Integer overflow occurs when the value assignedto an integer variable is more than its
maximum possible value
Integer underflow occurs when the value is
assigned to an integer is less than possible
minimum value
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Variables
A variable is a named memory location or memory cell
It is used to store programs input data and itscomputational results during execution
The value of a variable is changed during the executionof program
The value stored in a variable is referred by variable
nameThe variables are created in RAM
Data stored in variable is temporary
It can be used and processed during the execution of theprogram
The data stored in the variables is automaticallyremoved when program ends
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The value of a variable is changed during
program execution but its name will remain
same
Marks
10
Name of variable
Location of variable
Computer memory
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Variables declaration
The process of specifying the variable name and its typeis called variable declaration
All variable must be declared before they are used in theprogram
Compiler uses the declaration to determine how muchmemory is needed for each variable
Different type of variables require different amount ofmemory
The required number of bytes are allocated when avariable is declared
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Syntax
The syntax of declaring variable is as follows
Data- type variable-name ;Data type it indicates type of data that can be stored in
variable
Variable name refers to memory location of the variable
Int marks;
float avg;
Double salary;
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Variable initialization
The process of assigning a value to a variable at the time ofdeclaration
The equal sign is used to initialize a variableSyntax
Typename variable = value ;
Type name indicates the data type of the variable to be initialized
Variable name of the variable to be initialized= assignment operator
Value it is the value to initialize a variable
Int n =100;
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Constant
Constant is the quantity that cannot be change duringthe program execution
Types
Literal constant
Symbolic constant
Literal constant is a value that is typed directly in theprogram
It appears in the program where it is needed
Hello world is string literal constant
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Types of literal constants
Integer constantFloating point constant
Character constant
String constant
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Symbolic constant
A symbolic constant is a name given to the values that
can no be changed
Symbolic constants are used to represent a value that is
frequently used in the program
Types of symbolic constantConst qualifier
Define Directive
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Const Qualifier
Const qualifier is used to define a constant
Const is declared by its name and its data type
The const must be initialized with some value theinitialized value can not be changed during the
program executionSyntax
Const data type identifier=value;
Const int N=100;
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Define directive
Also used to define a constant
It does not specify the data type of the constant
Define directive starts with # symbol
It is not terminated with semicolon
Syntax
#define identifier value
# starts of preprocessor directive
Define used to define a constant
Identifier it is the name of constant
Value it represents the value associated with theidentifier
#define PI3.141593