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1.
What is Polymorphism
'Polymorphism' is an object oriented term.
Polymorphism may be defined as the ability of related objects to respond
to the same message with different, but appropriate actions. In other
words, polymorphism means taking more than one form. Polymorphism leads
to two important aspects in Object Oriented terminology - Function
Overloading and Function Overriding. Overloading is the practice of
supplying more than one definition for a given function name in the same
scope. The compiler is left to pick the appropriate version of the
function or operator based on the arguments with which it is called.
Overriding refers to the modifications made in the sub class to the
inherited methods from the base class to change their behavior.
2.
What is Operator overloading
When an operator is overloaded, it takes on an
additional meaning relative to a certain class. But it can still retain
all of its old meanings.
Examples:
1) The operators >> and << may be used for I/O operations
because in the header, they are overloaded.
2) In a stack class it is possible to overload the + operator so that
it appends the contents of one stack to the contents of another. But the
+ operator still retains its original meaning relative to other types of
data.
3.
What are Templates
C++ Templates allow u to generate families of
functions or classes that can operate on a variety of different data
types, freeing you from the need to create a separate function or class
for each type. Using templates, u have the convenience of writing a
single generic function or class definition, which the compiler
automatically translates into a specific version of the function or
class, for each of the different data types that your program actually
uses. Many data structures and algorithms can be defined independently
of the type of data they work with. You can increase the amount of
shared code by separating data-dependent portions from data-independent
portions, and templates were introduced to help you do that.
4.
What
is the difference between run time binding and compile time binding?
Dynamic Binding :
The address of the functions are determined at runtime rather than @
compile time. This is also known as "Late Binding".
Static Binding :
The address of the functions are determined at compile time rather than
@ run time. This is also known as "Early Binding"
5.
What
is Difference Between C/C++
C does not have a class/object concept.
C++ provides data abstraction, data encapsulation, Inheritance and
Polymorphism.
C++ supports all C syntax.
In C passing value to a function is "Call by Value" whereas in
C++ its "Call by Reference"
File extension is .c in C while .cpp in C++.(C++ compiler compiles the
files with .c extension but C compiler can not!)
In C structures can not have contain functions declarations. In C++
structures are like classes, so declaring functions is legal and
allowed.
C++ can have inline/virtual functions for the classes.
c++ is C with Classes hence C++ while in c the closest u can get to an
User defined data type is struct and union
6.
What will be the output of the following code?
7.
void main ()
8.
{ int i = 0 ,
a[3] ;
9.
a[i] = i++;
10.
printf ("%d",a[i])
;
}
The output for the above code would be a garbage
value. In the statement a[i] = i++; the value of the variable i would
get assigned first to a[i] i.e. a[0] and then the value of i would get
incremented by 1. Since a[i] i.e. a[1] has not been initialized, a[i]
will have a garbage value.
11.
Why doesn't the following code give the desired result?
int x = 3000, y = 2000 ;
long int z = x * y ;
Here the multiplication is carried out between two ints x and y, and the
result that would overflow would be truncated before being assigned to
the variable z of type long int. However, to get the correct output, we
should use an explicit cast to force long arithmetic as shown below:
long int z = ( long int ) x * y ;
Note that ( long int )( x * y ) would not give the desired effect.
12.
Why doesn't the following statement work?
char str[ ] = "Hello" ;
strcat ( str, '!' ) ;
The string function strcat( ) concatenates strings and not a character.
The basic difference between a string and a character is that a string
is a collection of characters, represented by an array of characters
whereas a character is a single character. To make the above statement
work writes the statement as shown below:
strcat ( str, "!" ) ;
13.
How do I know how many elements an array can hold?
The amount of memory an array can consume depends
on the data type of an array. In DOS environment, the amount of memory
an array can consume depends on the current memory model (i.e. Tiny,
Small, Large, Huge, etc.). In general an array cannot consume more than
64 kb. Consider following program, which shows the maximum number of
elements an array of type int, float and char can have in case of Small
memory model.
main( )
{
int i[32767] ;
float f[16383] ;
char s[65535] ;
}
14.
How do I write code that reads data at memory location specified by
segment and offset?
Use peekb( ) function. This function returns
byte(s) read from specific segment and offset locations in memory. The
following program illustrates use of this function. In this program from
VDU memory we have read characters and its attributes of the first row.
The information stored in file is then further read and displayed using
peek( ) function.
#include
<stdio.h>
#include <dos.h>
main(
)
{
char
far *scr = 0xB8000000 ;
FILE *fp ;
int offset ;
char ch ;
if
( ( fp = fopen ( "scr.dat", "wb" ) ) == NULL )
{
printf
( "\nUnable to open file" ) ;
exit( ) ;
}
//
reads and writes to file
for ( offset = 0 ; offset < 160 ; offset++ )
fprintf ( fp, "%c", peekb ( scr, offset ) ) ;
fclose ( fp ) ;
if
( ( fp = fopen ( "scr.dat", "rb" ) ) == NULL )
{
printf
( "\nUnable to open file" ) ;
exit( ) ;
}
//
reads and writes to file
for ( offset = 0 ; offset < 160 ; offset++ )
{
fscanf
( fp, "%c", &ch ) ;
printf ( "%c", ch ) ;
}
fclose
( fp ) ;
}
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