CBSE Class 11 Computer Science Introduction To C++ Notes

Introduction to C++

C++ CHARACTER SET

Character set is asset of valid characters that a language can recognize . A character can represents any letter, digit, or any other sign . Following are some of the C++

character set.

LETTERS                                 A to Z and a to z

DIGITS                                       0 -9

SPECIAL SYMBOLS            + -* ^ \ [] {} = != < > . ‗ ‗ ; : & #

WHITE SPACE                   Blankl space , horizontal tab ( - > ), carriage return , Newline, Form feed.

OTHER CHARACTERS      256 ASCII characters as data or as literals.

TOKENS:

The smallest lexical unit in a program is known as token. A token can be any keyword,Identifier,Literals, Puncutators, Operators.

KEYWORDS :

These are the reserved words used by the compiler. Following are some of the Keywords.                                     

 auto           continue         float        new       signed         volatile

short          long               class           struct     else           inline

delete          friend          private          typedef              void           template

catch           friend          sizeof             union             register        goto

IDENTIFIERS:

An arbitrary name consisting of letters and digits to identify a particular word.C++ iscase sensitive as nit treats upper and lower case letters differently. The first character must be a letter . the underscore counts as a letter

Pen        time580            s2e2r3          _dos       _HJI3_JK

LITERALS:

The data items which never change their value throughout the program run. There are several kind of literals:

• Integer constant

• Character constant

• Floating constant

• String constant.

Integer constant :

Integer constant are whole numbers without any fractional part. An integer constant must have at least one digit and must not contain any decimal point. It may contain either + or _. A number with no sign is assumed as positive.        e.g 15, 1300, -58795.

Character Constant:

A character constant is single character which is enclosed within single quotation marks.    e.g ‗ A‘

Floating constant:

Numbers which are having the fractional part are referred as floating numbers or real constants. it may be a positive or negative number. A number with no sign is assumed to be a positive number.                                                            e.g 2.0, 17.5, -0.00256

String Literals:

It is a sequence of letters surrounded by double quotes. E.g ―abc‖.

PUNCTUATORS:

The following characters are used as punctuators which are also know as separators in C++ 

OPERATORS:

These are those lexical units that trigger some computation when applied to variables and other objects in an expression. Following are some operators used in C++ Unary operators: Those which require only one operand to trigger. e.g. & , + , ++ , -- ! . Binary operators: these require two operands to operate upon. Following are some of the Binary operators.

Arithmatic operators :

+                 Addition

_                ubstraction

A*            Multiplication

/             Division

%         Remainder.

Logical Operators :

&& -     logical AND          || -        Logical OR

Relational Operator:

<     less than

a>   Greater than

<=     Less than equal to.

>=       greater than equal to.

==        equal to.

!=     not equal to.

Conditional operator:         ? (question )   : ( colon )

Assignment Operator:

= assignment operator
*= Assign Product.
/= Assign quotient
%= assign Remainder
&= Assign bitwise AND
^= Assign bitwise XOR.
|=Assign bitwise OR

Conditional operator ( ? )

The conditional operator evaluates an expression returning a value if that expression is true and a different one if the expression is evaluated as false. Its format is:

condition ? result1 : result2

e.g 7==5 ? 4 : 3 // returns 3, since 7 is not equal to 5.

Comma operator ( , )

The comma operator (,) is used to separate two or more expressions that are included where only one expression is expected. When the set of expressions has to be evaluated for a value, only the rightmost expression is considered.

For example, the following code:

a = (b =3 , b +2 );
Would first assign the value 3 to b, and then assign b+2 to variable a. So, at the end, variable a would contain the value 5 while variable b would contain value 3.

Explicit type casting operator

Type casting operators allow you to convert a datum of a given type to another. There are several ways to do this in C++. The simplest one, which has been inherited from the C language, is to precede the expression to be converted by the new type enclosed between parentheses ( ) :

int i;

float f =3014;
i = ( int ) f; 

The previous code converts the float number 3.14 to an integer value (3), the remainder is lost. Here,the typecasting operator was (int). Another way to do the same thing in C++ is using the functional notation: preceding the expression to be converted by the type and enclosing the expression between parentheses:

i = int (f );

Both ways of type casting are valid in C++.
sizeof()

This operator accepts one parameter, which can be either a type or a variable itself and returns the size in bytes of that type or object:
a= sizeof (char);
This will assign the value 1 to a because char is a one-byte long type.
The value returned by sizeof is a constant, so it is always determined before program execution.
Input Output (I/O) In C++
The cout Object:
The cout object sends to the standard output device. cout sends all out put to the screen i.e monitor.
The syntax of cout is as follows:
cout<< data;.
e.g
cout<< a ; ( here a can be any variable)

The cin operator :
The cin operator is used to get input from the keyboard. When a program reaches the line with cin, the user at the keyboard can enter values directly into variables.
The syntax of cin is as follows:
cin>> variablename
e.g
cin>> ch; ( here ch can be any variable)

• Basic structure of a C++ program:
Following is the structure of a C++ program tht prints a string on the screen:
#include<iostream.h>
void main ()
{
cout<<‖ Study material for Class XI‖;
} 

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