C ++ Fundamentals
Objectives
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History of C ++
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Identifiers
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Escape Sequences
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Keywords
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Data types
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Variables and constants
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Operators
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Input and output
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Manipulators
History of C++ :
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C ++ evolved from C, which evolved from 2 previous programming languages,
BPCL and B.
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C++ an extension of C, was developed by Bjarne Stroustrup in early 1980s at
Bell Laboratories.
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C++ provides capabilities for object-oriented programming.
Program : Write a program in C++ to print a message – Welcome to C++
// Program to display a message on the screen
#include<iostream.h>
int main( )
{
cout << “ Welcome to C ++ ” ;
return 0 ; // indicates the program ended successfully
}
Let us examine the various components of the above program
Comments: Any set of characters following // indicates that remainder of the line is a
comment. Programmers insert comments to document programs and improve program
readability. Comments also help other people read and understand your program.
Comments do not cause the computer to perform any action when the program is run.
The C++ compiler ignores comments. Comments that begin with // are called single line
comments because the comment terminates at the end of the current line.
#include<iostream.h> : is a preprocessor directive. i.e. a message to C++ preprocessor.
Lines beginning with
# are processed by the preprocessor before the program is
compiled. This specific line tells the preprocessor to include in program contents of
input/output stream header file. It contains declarations for identifier cout and <<
operator. Header file <iostream.h> should be included at beginning of all programs that
use input/output stream.
Function main( ) : Functions are one of fundamental blocks of C++. C++ programs
contain one or more functions, exactly one of which must be main(). C++ programs
begin executing at function main( ) even if main( ) is not the first function in the program.
Keyword int to the left of main( ) indicates that main( ) returns an integer value. An
opening brace ( { ) marks beginning of the function body and the corresponding closing
brace ( } ) the end of the function body.
Program statements:
programming. Line
The program statement is the fundamental unit of C++
cout << “ Welcome to C ++ ” ; instructs the computer to print
on the screen the string of characters contained between quotation marks. The entire
line including cout , the << operator, the string and the semicolon is called a statement.
Every statement must end with a semicolon ( also known as statement terminator) Output
and input in C++ is accomplished with stream of characters. The identifier cout (
pronounced as ‘C out’ ) is a predefined object that represents the standard output stream
in C++. Thus when the above statement is executed , it sends the stream of characters
Welcome to C ++ to the standard output stream object – cout – which is normally
connected to the screen. The operator << is called the stream insertion operator. The
value to the right of the operator, the right operand , is inserted in output stream.
return 0 :
This is included at the end of every main() function. C++ keyword return is
one of several ways to exit out of a function. The value 0 indicates that the program has
terminated successfully.
Screen
cout
<<
Variable
Output with cout
Identifiers:
Identifiers are names of variables, functions, arrays, classes created by the
programmer.
Rules for naming identifiers
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An identifier is a series of characters consisting of letters, digits, and
underscores( _ ) that does not begin with a digit.
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C++ is case sensitive – uppercase and lowercase letters are different.
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Key words or reserved words cannot be used as identifiers
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C++ allows identifiers of any length, but your system and/or C++
implementation may impose some restrictions on the length of identifiers. Use
identifiers of 31 characters or fewer to ensure portability.
Escape Sequences
Escape Sequence
Description
\n
Newline. Position the cursor to the beginning of the next line
\t
Horizontal tab. Move the cursor the the next tab stop
\r
Carriage return. Position the screen cursorto the beginning of
the current line; do not advance to the next line
\a
Alert. Sound the system bell
\b
Backspace. Move the cursor one position to the left
\\
Backslash. Used to print a backslash character
\”
Double quotation marks. Used to print a double quote
character
\f
Form feed
Keywords in C++
Keywords common to C and C++ programming languages
auto
break
case
char
const
continue default
do
double
else
enum
extern
float
for
goto
if
int
long
short
signed sizeof
static
struct
switch typedef
register return
union
unsigned void
volatile while
C++ only keywords
asm
bool
catch
class
const_cast delete
false
friend
inline
mutable namespace new
protected public static_cast template this
typeid
typename using
virtual
wchar_t
throw
dynamic_cast
explicit
operator
private
true
try
reinterpret_cast
Data types
Data is differentiated into various types. The type of data element restricts the data
element to assume a particular set of values.
The basic data types are
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character (char) – A character in C character set
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integer (int ) – An integer
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float – a single precision floating point number
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double – a double precision floating point number.
In addition qualifiers short and long may be applied to same of above data types.
Thus we have following additional data types.
short int – abbreviated as short
long int – also abbreviated as long
long double - an extended double precision floating point number
The qualifiers signed and unsigned may be applied to char, short, int, long unsigned
variables can only have non-negative values, while signed variable can have both positive
and negative values. In absence of explicit unsigned specification int , short, long are
considered to be signed.
Data type
Description
Typical memory
requirements
Range
char
Single character
8 bits
-128 to 127
unsigned
char
Single character
8 bits
0 to 255
signed char
Single character
8 bits
-128 to 127
16 bits
-32768 to 32767
16 bits
0 to 65535
16 bits
-32768 to 32767
int
unsigned int
short int
Positive and
negative whole
numbers
including 0
Positive whole
numbers
including 0
unsigned
short int
16 bits
0 to 65535
signed short
int
16 bits
-32768 to 32767
long int
32 bits
signed long
int
32 bits
unsigned
long int
float
double
32 bits
Floating point
number (number
containing
decimal point
and / or exponent)
Double precision
floating point
number (more
significant figures
and an exponent,
which may be
larger in
magnitude.
32 bits
64 bits
Variables and Constants
Variable is an object or entity used by a program to store values in computation.
Variables may change value during execution. All variables must be declared with a
name and data type before they can be used in a program.
Manipulators
Manipulators are operators used with insertion operator << to format or modify the way
data is displayed
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endl : is an abbreviation for end line. This is a manipulator that causes the line
feed to be inserted into the stream. endl is same as non-graphic character to
generate line feed (\n). endl is an example of non parameterized stream
manipulator and does not require the iomanip.h header file.
// An example of endl
#include<iostream.h>
int main()
{
cout << “Hello ” << endl ;
cout << “World ” << endl ;
return 0 ;
}
Output:
Hello
World
// An example of endl
#include<iostream.h>
int main()
{
int a = 20;
cout << “a = ” << a << endl ;
cout << “a = ” << a << “\n” ;
return 0 ;
}
Output:
a = 20
a = 20
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setw( n) : stands for set width. The setw manipulator is used to specify the
minimum number of character positions on output field a variable will occupy.
e.g. setw ( 4 ) specifies the next value output is printed in the field width of 4
spaces. If the value to be output is less than 4 character positions wide, the value
is right justified in the field by default. On the other hand if the value to be
displayed is more than 4 character positions wide field width is extended to
accommodate entire value.
// An example of setw
#include <iostream.h>
#include<iomanip.h>
int main ()
{
int a = 200 , b = 300;
cout << setw ( 5 ) << a << setw(5) << b << endl ;
cout << setw ( 8 ) << a << setw(8) << b << endl ;
return 0;
}
Output:
_ _ 200_ _ 300
_ _ _ _ _ 200 _ _ _ _ _ 300
<iomanip.h> : A header file under which declarations for manipulators are stored.
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setprecision (p) : is used to control the number of digits to the right of the
decimal point. The default precision is 6.
// An example of setprecision
#include <iostream.h>
#include<iomanip.h>
int main ()
{
float a = 5 , b = 3 , c ;
c = a / b;
cout << setprecision ( 1 ) << c << endl ;
cout << setprecision ( 2 ) << c << endl ;
cout << setprecision ( 5 ) << c << endl ;
return 0;
}
Output:
1.7
1.67
1.66667