1.
How many times "IndiaBIX" is get printed?
#include<stdio.h>
int main()
{
int x;
for(x=-1; x<=10; x++)
{
if(x < 5)
continue;
else
break;
printf("IndiaBIX");
}
return 0;
}
Answer. 1)c
Write a c program to print Hello world without using
any semicolon.
Explanation:
Solution: 1
void main(){
if(printf("Hello world")){
}
}
Solution: 2
void main(){
while(!printf("Hello world")){
}
}
Solution: 3
void main(){
switch(printf("Hello world")){
}
}
Swap two variables without using third variable.
Explanation:
#include<stdio.h>
int main(){
int a=5,b=10;
//process one
a=b+a;
b=a-b;
a=a-b;
printf("a= %d
b=
%d",a,b);
//process two
a=5;
b=10;
a=a+b-(b=a);
printf("\na= %d
//process three
a=5;
b=10;
a=a^b;
b=a^b;
b=
%d",a,b);
a=b^a;
printf("\na= %d
b=
%d",a,b);
b=
%d",a,b);
//process four
a=5;
b=10;
a=b-~a-1;
b=a+~b+1;
a=a+~b+1;
printf("\na= %d
//process five
a=5,
b=10;
a=b+a,b=a-b,a=a-b;
printf("\na= %d
b=
%d",a,b);
return 0;
}
3
What is dangling pointer in c?
Explanation:
Dangling pointer:
If any pointer is pointing the memory address of any
variable but after some variable has deleted from that
memory
location while pointer
memory
location.
Such
pointer
is
still
is
pointing
known
as
such
dangling
pointer and this problem is known as dangling pointer
problem.
Initially:
Later:
For example:
What will be output of following c program?
#include<stdio.h>
int *call();
int main(){
int *ptr;
ptr=call();
fflush(stdin);
printf("%d",*ptr);
return 0;
}
int * call(){
int x=25;
++x;
return &x;
}
Output: Garbage value
Note: In some compiler you may get warning
message returning address of local variable or
temporary
Explanation: variable x is local variable. Its scope
and lifetime is within the function call hence after
returning address of x variable x became dead and
pointer is still pointing ptr is still pointing to that
location.
Solution of this problem:
Make the variable x is as static variable. In other
word we can say a pointer whose pointing object
has been deleted is called dangling pointer.
#include<stdio.h>
int *call();
int main(){
int *ptr;
ptr=call();
fflush(stdin);
printf("%d",*ptr);
return 0;
}
int * call(){
static int x=25;
++x;
return &x;
}
Output: 26
What is wild pointer in c?
Explanation:
A pointer in c which has not been initialized is known
as wild pointer.
Example:
What will be output of following c program?
int main(){
int *ptr;
printf("%u\n",ptr);
printf("%d",*ptr);
}
return 0;
Output: Any address
Garbage value
Here ptr is wild pointer because it has not been
initialized. There is difference between the NULL
pointer and wild pointer. Null pointer points the base
address of segment while wild pointer doesnt point any
specific memory location.
What are merits and demerits of array in c?
Explanation:
Merits:
(a) We can easily access each element of array.
(b) Not necessity to declare too many variables.
(c)
Array
location.
Demerit:
elements
are
stored
in
continuous
memory
(a) Wastage of memory space. We cannot change size of
array at the run time.
(b) It can store only similar type of data.
Do you know memory representation of int a = 7 ?
Explanation:
Memory representation of:
signed int a=7;
signed
short
(In Turbo c compiler)
int
a=7
equivalent
of
(Both
turbo
and
Linux
gcc
compiler)
Binary
data
in
16
bit:
first
15
00000000
00000111
Data
bit:
0000000
00000111 (Take
bit
form
side
i.e.
right side)
Sign bit: 0 (Take leftmost one bit)
First
eight
bit
of
data
bit
from
right
00000111 will store in the leftmost byte from right to
left side and rest seven bit of data bit i.e. 0000000
will store in rightmost byte from right to left side as
shown in the following figure:
What is and why array in c?
Explanation:
An array is derived data type in c programming language
which
can
store
similar
type
of
data
in
continuous
memory location. Data may be primitive type (int, char,
float, double), address of union, structure, pointer,
function or another array.
Example of array declaration:
int arr[5];
char arr[5];
float arr[5];
long double arr[5];
char * arr[5];
int (arr[])();
double ** arr[5];
Array is useful when:
(a) We have to store large number of data of similar
type.
If
we
have
large
number
of
similar
kind
of
variable then it is very difficult to remember name of
all variables and write the program. For example:
//PROCESS ONE
int main(){
int ax=1;
int b=2;
int cg=5;
int dff=7;
int am=8;
int raja=0;
int rani=11;
int xxx=5;
int yyy=90;
int p;
int q;
int r;
int avg;
avg=(ax+b+cg+dff+am+raja+rani+xxx+yyy+p+q+r)/12;
printf("%d",avg);
return 0;
}
If we will use array then above program can be written
as:
//PROCESS TWO
int main(){
int arr[]={1,2,5,7,8,0,11,5,50};
int i,avg;
for(int i=0;i<12;i++){
avg=avg+arr[i];
}
printf("%d",avg/12);
return 0;
}
Question: Write a C program to find out average of 200
integer number using process one and two.
(b) We want to store large number of data in continuous
memory location. Array always stores data in continuous
memory location.
What will be output when you will execute the following
program?
int main(){
int arr[]={0,10,20,30,40};
char *ptr=arr;
arr=arr+2;
printf("%d",*arr);
return 0;
}
Advantage of using array:
1. An array provides singe name .So it easy to remember
the name of all element of an array.
2. Array name gives base address of an array .So with
the help increment operator we can visit one by one all
the element of an array.
3. Array has many application data structure.
Array of pointers in c:
Array whose content is address of another variable is
known as array pointers.
For example:
int main(){
float a=0.0f,b=1.0f,c=2.0f;
float * arr[]={&a,&b,&c};
b=a+c;
printf("%f",arr[1]);
return 0;
}
Why we use do-while loop in c? Also tell any properties
which you know?
Explanation:
It is also called as post tested loop. It is used when
it is necessary to execute the loop at least one time.
Syntax:
do {
Loop body
} while (Expression);
Example:
int main(){
int num,i=0;
do{
printf("To enter press 1\n");
printf("To exit press
2");
scanf("%d",&num);
++i;
switch(num){
case 1:printf("You are welcome\n");break;
default : exit(0);
}
}
while(i<=10);
return 0;
}
Output: 3 3 4 4
If there is only one statement in the loop body then
braces is optional. For example:
(a)
int main(){
double i=5.5678;
do
printf("hi");
while(!i);
return 0;
}
Output: 3 3 4 4
(b)
int main(){
double i=5.63333;
do
printf("hi");
while(!i);
return 0;
}
Output: hi
(c)
int main(){
int x=25,y=1;
do
if(x>5)
printf(" ONE");
else if(x>10)
printf(" TWO");
else if(x==25)
printf(" THREE");
else
printf(" FOUR");
while(y--);
return 0;
}
Output: ONE ONE
What is the meaning of prototype of a function?
Explanation:
Prototype of a function
Declaration
of
function
is
known
as
prototype
function. Prototype of a function means
(1) What is return type of function?
(2) What parameters are we passing?
(3) For example prototype of printf function is:
int printf(const char *, );
of
I.e.
its
return
type
parameter
constant
parameter
is
is
int
character
ellipsis
i.e.
data
type,
pointer
variable
its
and
first
second
number
of
arguments.
Write a c program to modify the constant variable in c?
Explanation:
You
can
modify
constant
variable
with
the
help
of
pointers. For example:
#include<stdio.h>
int main(){
int i=10;
int *ptr=&i;
*ptr=(int *)20;
printf("%d",i);
return 0;
}
Output: 20
Write a c program to modify the constant variable in c?
Explanation:
You
can
modify
constant
pointers. For example:
variable
with
the
help
of
#include<stdio.h>
int main(){
int i=10;
int *ptr=&i;
*ptr=(int *)20;
printf("%d",i);
return 0;
}
Output: 20
What is pointer to a function?
Explanation:
(1) What will be output if you will execute following
code?
int * function();
int main(){
auto int *x;
int *(*ptr)();
ptr=&function;
x=(*ptr)();
printf("%d",*x);
}
int *function(){
static int a=10;
return &a;
}
Output: 10
Explanation: Here function is function whose parameter
is void data type and return type is pointer to int
data type.
x=(*ptr)()
=> x=(*&functyion)() //ptr=&function
=> x=function() //From rule *&p=p
=> x=&a
So, *x = *&a = a =10
(2) What will be output if you will execute following
code?
int find(char);
int(*function())(char);
int main(){
int x;
int(*ptr)(char);
ptr=function();
x=(*ptr)('A');
printf("%d",x);
return 0;
}
int find(char c){
return c;
}
int(*function())(char){
return find;
}
Output: 65
Explanation: Here function whose name is function which
passing void data type and returning another function
whose parameter is char data type and return type is
int data type.
x=(*ptr)(A)
=> x= (*function ()) (A) //ptr=function ()
//&find=function () i.e. return type of function ()
=> x= (* &find) (A)
=> x= find (A) //From rule*&p=p
=> x= 65
(3) What will be output if you will execute following
code?
char * call(int *,float *);
int main(){
char *string;
int a=2;
float b=2.0l;
char *(*ptr)(int*,float *);
ptr=&call;
string=(*ptr)(&a,&b);
printf("%s",string);
return 0;
}
char *call(int *i,float *j){
static char *str="c-pointer.blogspot.com";
str=str+*i+(int)(*j);
return str;
}
Output: inter.blogspot.com
Explanation: Here call is function whose return type is
pointer to character and one parameter is pointer to
int data type and second parameter is pointer to float
data type and ptr is pointer to such function.
str= str+*i+ (int) (*j)
=c-pointer.blogspot.com + *&a+ (int) (*&b)
//i=&a, j=&b
=c-pointer.blogspot.com + a+ (int) (b)
=c-pointer.blogspot.com +2 + (int) (2.0)
=c-pointer.blogspot.com +4
=inter.blogspot.com
(4) What will be output if you will execute following
code?
char far * display(char far*);
int main(){
char far* string="cquestionbank.blogspot.com";
char far *(*ptr)(char far *);
ptr=&display;
string=(*ptr)(string);
printf("%s",string);
}
char far *display(char far * str){
char far * temp=str;
temp=temp+13;
*temp='\0';
return str;
}
Output: cquestionbak
Explanation: Here display is function whose parameter
is pointer to character and return type is also pointer
to character and ptr is its pointer.
temp is char pointer
temp=temp+13
temp=\0
Above two lines replaces first dot character by null
character of string of variable string i.e.
"cquestionbank\0blogspot.com"
As we know %s print the character of stream up to null
character.
(Q)Write a c program to find size of
structure without using sizeof operator?
Explanation:
struct
ABC{
int a;
float b;
char c;
};
int main(){
struct ABC *ptr=(struct ABC *)0;
ptr++;
printf("Size of structure is: %d",*ptr);
return 0;
}
What is NULL pointer?
Explanation:
Literal meaning of NULL pointer is a pointer which is
pointing to nothing. NULL pointer points the base
address of segment.
Examples of NULL pointer:
1.
2.
3.
4.
5.
6.
int *ptr=(char *)0;
float *ptr=(float *)0;
char *ptr=(char *)0;
double *ptr=(double *)0;
char *ptr=\0;
int *ptr=NULL;
What is meaning of NULL?
Answer:
NULL is macro constant which has been defined in the
heard file stdio.h, alloc.h, mem.h, stddef.h and
stdlib.h as
#define NULL 0
Examples:
(1)What will be output of following c program?
#include "stdio.h"
int main(){
if(!NULL)
printf("I know preprocessor");
else
printf("I don't know preprocessor");
}
Output: I know preprocessor
Explanation:
!NULL = !0 = 1
In if condition any non zero number mean true.
(2)What will be output of following c program?
#include "stdio.h"
int main(){
int i;
static int count;
for(i=NULL;i<=5;){
count++;
i+=2;
}
printf("%d",count);
}
Output: 3
(3)What will be output of following c program?
#include "stdio.h"
int main(){
#ifndef NULL
#define NULL 5
#endif
printf("%d",NULL+sizeof(NULL));
}
Output: 2
Explanation:
NULL + sizeof(NULL)
=0 + sizeoof(0)
=0+2 //size of int data type is two byte.
We cannot copy anything in the NULL pointer.
Example:
(4)What will be output of following c program?
#include "string.h"
int main(){
char *str=NULL;
strcpy(str,"c-pointer.blogspot.com");
printf("%s",str);
return 0;
}
Output: (null)
What is difference between pass by value and pass by
reference?
Explanation:
In c we can pass the parameters in a function in two
different ways.
(a)Pass by value: In this approach we pass copy of
actual variables in function as a parameter. Hence any
modification on parameters inside the function will not
reflect in the actual variable. For example:
#include<stdio.h>
int main(){
int a=5,b=10;
swap(a,b);
printf("%d
%d",a,b);
return 0;
}
void swap(int a,int b){
int temp;
temp =a;
a=b;
b=temp;
}
Output: 5
10
(b)Pass by reference: In this approach we pass memory
address actual variables in function as a parameter.
Hence any modification on parameters inside the
function will reflect in the actual variable. For
example:
#incude<stdio.h>
int main(){
int a=5,b=10;
swap(&a,&b);
printf("%d %d",a,b);
return 0;
}
void swap(int *a,int *b){
int
*temp;
*temp =*a;
*a=*b;
*b=*temp;
}
Output: 10 5
What is size of void pointer?
Explanation:
Size of any type of pointer in c is independent of data
type which is pointer is pointing i.e. size of all type
of pointer (near) in c is two byte either it is char
pointer,
double
pointer,
function
pointer
or
null
pointer.
Void pointer is not exception of this rule
and size of void pointer is also two byte.
What is difference between uninitialized pointer and
null pointer?
Explanation:
An uninitialized pointer is a pointer which points
unknown memory location while null pointer is pointer
which points a null value or base address of segment.
For example:
int *p;
//Uninitialized pointer
int *q= (int *)0;
//Null pointer
#include<stdio.h>
int *r=NULL;
//Null pointer
What will be output of following c program?
#include<string.h>
#include<stdio.h>
int main(){
char *p;
//Uninitialized pointer
char *q=NULL;
//Null pointer;
strcpy(p,"cquestionbank");
strcpy(q,"cquestionbank");
printf("%s
%s",p,q);
return 0;
}
Output: cquestionbank (null)
Can you read complex pointer declaration?
Explanation:
Rule 1. Assign the priority to the pointer declaration
considering precedence and associative according to
following table.
(): This operator behaves as bracket operator or
function operator.
[]: This operator behaves as array subscription
operator.
*: This operator behaves as pointer operator not as
multiplication operator.
Identifier: It is not an operator but it is name of
pointer variable. You will always find the first
priority will be assigned to the name of pointer.
Data type: It is also not an operator. Data types also
includes modifier (like signed int, long double etc.)
You will understand it better by examples:
(1) How to read following pointer?
char (* ptr)[3]
Answer:
Step 1: () and [] enjoys equal precedence. So rule of
associative will decide the priority. Its associative
is left to right so first priority goes to ().
Step 2: Inside the bracket * and ptr enjoy equal
precedence. From rule of associative (right to left)
first priority goes to ptr and second priority goes to
*.
Step3: Assign third priority to [].
Step4: Since data type enjoys least priority so assign
fourth priority to char.
Now read it following manner:
ptr is pointer to such one dimensional array of size
three which content char type data.
(2) How to read following pointer?
float (* ptr)(int)
Answer:
Assign the priority considering precedence and
associative.
Now read it following manner:
ptr is pointer to such function whose parameter is int
type data and return type is float type data.
Rule 2: Assign the priority of each function parameter
separately and read it also separately. Understand it
through following example.
(3) How to read following pointer?
void (*ptr)(int (*)[2],int (*) void))
Answer:
Assign the priority considering rule of
precedence and associative.
Now read it following manner:
ptr is pointer to such function which first parameter
ispointer to one dimensional array of size two which
contentint type data and second parameter is pointer to
such function which parameter is void and return type
is int data type and return type is void.
(4) How to read following pointer?
int ( * ( * ptr ) [ 5 ] ) ( )
Answer:
Assign the priority considering rule of
precedence and associative.
Now read it following manner:
ptr is pointer to such array of size five which content
are pointer to such function which parameter is void
and return type is int type data.
(5) How to read following pointer?
double*(*(*ptr)(int))(double **,char c)
Answer:
Assign the priority considering rule of precedence and
associative.
Now read it following manner:
ptr is pointer to function which parameter is int type
data and return type is pointer to function which first
parameter is pointer to pointer of double data type and
second parameter is char type data type and return type
ispointer to double data type.
(6) How to read following pointer?
unsigned **(*(*ptr)[8](char const *, ...)
Answer:
Assign the priority considering rule of precedence and
associative.
Now read it following manner:
ptr is pointer to array of size eight and content of
array is pointer to function which first parameter is
pointer to character constant and second parameter is
variable number of arguments and return type
is pointer to pointer ofunsigned int data type.
What is the far pointer in c?
Explanation:
The pointer which can point or access whole the
residence memory of RAM i.e. which can access all 16
segments is known as far pointer.
Size of far pointer is 4 byte or 32 bit. Examples:
(1) What will be output of following c program?
int main(){
int x=10;
int far *ptr;
ptr=&x;
printf("%d",sizeof ptr);
return 0;
Output: 4
(2)What will be output of following c program?
int main(){
int far *near*ptr;
printf("%d %d",sizeof(ptr) ,sizeof(*ptr));
return 0;
}
Output: 4 2
Explanation: ptr is far pointer while *ptr is near
pointer.
(3)What will be output of following c program?
int main(){
int far *p,far *q;
printf("%d %d",sizeof(p) ,sizeof(q));
}
Output: 4 4
First 16 bit stores: Segment number
Next 16 bit stores: Offset address
Example:
int main(){
int x=100;
int far *ptr;
ptr=&x;
printf("%Fp",ptr);
return 0;
}
Output: 8FD8:FFF4
Here 8FD8 is segment address and FFF4 is offset address
in hexadecimal number format.
Note: %Fp is used for print offset and segment address
of pointer in printf function in hexadecimal number
format.
In the header file dos.h there are three macro
functions to get the offset address and segment address
from far pointer and vice versa.
1. FP_OFF(): To get offset address from far address.
2. FP_SEG(): To get segment address from far address.
3. MK_FP(): To make far address from segment and offset
address.
Examples:
(1)What will be output of following c program?
#include "dos.h"
int main(){
int i=25;
int far*ptr=&i;
printf("%X %X",FP_SEG(ptr),FP_OFF(ptr));
}
Output: Any segment and offset address in hexadecimal
number format respectively.
(2)What will be output of following c program?
#include "dos.h"
int main(){
int i=25;
int far*ptr=&i;
unsigned int s,o;
s=FP_SEG(ptr);
o=FP_OFF(ptr);
printf("%Fp",MK_FP(s,o));
return 0;
Output: 8FD9:FFF4 (Assume)
Note: We cannot guess what will be offset address;
segment address and far address of any far pointer
.These address are decided by operating system.
Limitation of far pointer:
We cannot change or modify the segment address of given
far address by applying any arithmetic operation on it.
That is by using arithmetic operator we cannot jump
from one segment to other segment. If you will
increment the far address beyond the maximum value of
its offset address instead of incrementing segment
address it will repeat its offset address in cyclic
order.
Example:
(q)What will be output of following c program?
int main(){
int i;
char far *ptr=(char *)0xB800FFFA;
for(i=0;i<=10;i++){
printf("%Fp \n",ptr);
ptr++;
}
return 0;
}
Output:
B800:FFFA
B800:FFFB
B800:FFFC
B800:FFFD
B800:FFFE
B800:FFFF
B800:0000
B800:0001
B800:0002
B800:0003
B800:0004
This property of far pointer is called cyclic nature of
far pointer within same segment.
Important points about far pointer:
1. Far pointer compares both offset address and segment
address with relational operators.
Examples:
(1)What will be output of following c program?
int main(){
int far *p=(int *)0X70230000;
int far *q=(int *)0XB0210000;
if(p==q)
printf("Both pointers are equal");
else
printf("Both pointers are not equal");
return 0;
}
Output: Both pointers are not equal
(2)What will be output of following c program?
int main(){
int far *p=(int *)0X70230000;
int far *q=(int *)0XB0210000;
int near *x,near*y;
x=(int near *)p;
y=(int near *)q;
if(x==y)
printf("Both pointer are equal");
else
printf("Both pointer are not equal");
return 0;
}
Output: Both pointers are equal
2. Far pointer doesnt normalize
What is a cyclic property of data type in c? Explain
with any example.
Explanation:
#include<stdio.h>
int main(){
signed char c1=130;
signed char c2=-130;
printf("%d
%d",c1,c2);
return 0;
}
Output: -126
126 (why?)
This situation is known as overflow of signed char.
Range of unsigned char is -128 to 127. If we will
assign a value greater than 127 then value of variable
will be changed to a value if we will move clockwise
direction as shown in the figure according to number.
If we will assign a number which is less than -128 then
we have to move in anti-clockwise direction.
