C Aptitude Questions and answers with explanation.

C Aptitude 1
C program aptitude questions, answers and explanation for interview preparations.
In this site, We discussed various type of C programs, now we are moving into further steps by looking at the c aptitude questions.
This questions and answers are helpful to freshers and job hunters. C interview questions are from various companies and experts.
Read more about C Programming Language . and read the C Programming Language (2nd Edition). by K and R.
Predict the output or error(s) for the following:

C aptitude 1.1

void main()
{
int const * p=5;
printf("%d",++(*p));
}

Answer: Compiler error: Cannot modify a constant value.

Explanation: p is a pointer to a “constant integer”. But we tried to change the value of the “constant integer”.

C aptitude 1.2

main()
{
char s[ ]="man";
int i;
for(i=0;s[ i ];i++)
printf("n%c%c%c%c",s[ i ],*(s+i),*(i+s),i[s]);
}


Answer: mmmm aaaa nnnn

Explanation: s[i], *(i+s), *(s+i), i[s] are all different ways of expressing the same idea. Generally array name is the base address for that array. Here s is the base address. i is the index number/displacement from the base address. So, indirecting it with * is same as s[i]. i[s] may be surprising. But in the case of C it is same as s[i].

C aptitude 1.3

 main()
{
float me = 1.1;
double you = 1.1;
if(me==you)
printf("I love U");
else
printf("I hate U");
}


Answer: I hate U

Explanation: For floating point numbers (float, double, long double) the values cannot be predicted exactly. Depending on the number of bytes, the precession with of the value represented varies. Float takes 4 bytes and long double takes 10 bytes. So float stores 0.9 with less precision than long double. Rule of Thumb: Never compare or at-least be cautious when using floating point numbers with relational operators (== , >, <, <=, >=,!= ) .

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C Program to count the number of occurrences of particular word in a string

C Program that counts the particular word in the given string. For example in the string ” the string is the set of charterers” , Number of occurrences of “the” is:2. Read more about C Programming Language .

/***********************************************************
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* for personal and learning purposes. For permissions to use the
* programs for commercial purposes,
* contact info@c-program-example.com
* To find more C programs, do visit www.c-program-example.com
* and browse!
* 
*                      Happy Coding
***********************************************************/

#include<stdio.h>

#include<string.h>

main()

{

 int strln,wordln,i,j,k,flag,count=0;

 char str[200],word[20];

 printf("Enter line of text:n");

 gets(str);

 printf("Enter the word to count:n");

 scanf("%s",word);

 strln=strlen(str);

 wordln=strlen(word);

 for(i=0;i<strln;i++)

 {

  if(str[i]==word[0]&&((str[i-1]==' '||i==0)&&(str[i+wordln]==' '||str[i+wordln]=='')))

  {

   for(flag=0,k=i+1,j=1;j<wordln;j++,k++)

   {

    if(str[k]==word[j])

    {

     flag++;

    }

   }

   if(flag==wordln-1)

   {

    count++;

   }

  }

 }

 printf("Number of occurence of '%s' = %dn",word,count);

}

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C program to delete n Characters from a given position in a given string.

C Strings:
C Program to delete the n characters from a given position from a given string. Here we use the gets() and puts() functions to read and write the string. delchar() function reads the character string and checks the length and position, then using strcpy() function it replaces the original string.Read more about C Programming Language .

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* programs for commercial purposes,
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*
* Happy Coding
***********************************************************/



#include <stdio.h>
#include <conio.h>
#include <string.h>

void delchar(char *x,int a, int b);

void main()
{
char string[10];
int n,pos,p;
clrscr();

puts("Enter the string");
gets(string);
printf("Enter the position from where to delete");
scanf("%d",&pos);
printf("Enter the number of characters to be deleted");
scanf("%d",&n);
delchar(string, n,pos);
getch();
}

// Function to delete n characters
void delchar(char *x,int a, int b)
{
if ((a+b-1) <= strlen(x))
{
strcpy(&x[b-1],&x[a+b-1]);
puts(x);
}
}


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C program to insert a sub-string in to given main string from a given position.

C Strings:
C Program to insert a sub-string in to given main string from a given position. In this program we read two strings and replace the second string in the given position of the first string.Read more about C Programming Language .

/***********************************************************
* You can use all the programs on www.c-program-example.com
* for personal and learning purposes. For permissions to use the
* programs for commercial purposes,
* contact info@c-program-example.com
* To find more C programs, do visit www.c-program-example.com
* and browse!
*
* Happy Coding
***********************************************************/



#include <stdio.h>
#include <conio.h>
#include <string.h>

void main()
{
char a[10];
char b[10];
char c[10];
int p=0,r=0,i=0;
int t=0;
int x,g,s,n,o;
clrscr();

puts("Enter First String:");
gets(a);
puts("Enter Second String:");
gets(b);
printf("Enter the position where the item has to be inserted: ");
scanf("%d",&p);
r = strlen(a);
n = strlen(b);
i=0;

// Copying the input string into another array
while(i <= r)
{
c[i]=a[i];
i++;
}
s = n+r;
o = p+n;

// Adding the sub-string
for(i=p;i<s;i++)
{
x = c[i];
if(t<n)
{
a[i] = b[t];
t=t+1;
}
a[o]=x;
o=o+1;
}

printf("%s", a);
getch();
}
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C program to implement stack.

Data structures using C,
Write a C program to implement stack. Stack is a data structure in which the objects are arranged in a non linear order. In stack, elements are added or deleted from only one end, i.e. top of the stack. Stack is a LIFO data structure. LIFO – Last in First Out Perform PUSH(insert operation), POP(Delete operation) and Display stack . Read more about C Programming Language .

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* programs for commercial purposes,
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*
* Happy Coding
***********************************************************/



#include <stdio.h>
#include <conio.h>
#define MAXSIZE 5

struct stack /* Structure definition for stack */
{
int stk[MAXSIZE];
int top;
};

typedef struct stack STACK;
STACK s;

/* Function declaration/Prototype*/

void push (void);
int pop(void);
void display (void);

void main ()
{
int choice;
int option = 1;

clrscr ();

s.top = -1;

printf ("STACK OPERATIONn");
while (option)
{
printf ("------------------------------------------n");
printf (" 1 --> PUSH n");
printf (" 2 --> POP n");
printf (" 3 --> DISPLAY n");
printf (" 4 --> EXIT n");
printf ("------------------------------------------n");

printf ("Enter your choicen");
scanf ("%d", &choice);

switch (choice)
{
case 1: push();
break;
case 2: pop();
break;
case 3: display();
break;
case 4: return;
}

fflush (stdin);
printf ("Do you want to continue(Type 0 or 1)?n");
scanf ("%d", &option);
}
}

/*Function to add an element to the stack*/
void push ()
{
int num;
if (s.top == (MAXSIZE - 1))
{
printf ("Stack is Fulln");
return;
}
else
{
printf ("Enter the element to be pushedn");
scanf ("%d", &num);
s.top = s.top + 1;
s.stk[s.top] = num;
}
return;
}


/*Function to delete an element from the stack*/
int pop ()
{
int num;
if (s.top == - 1)
{
printf ("Stack is Emptyn");
return (s.top);
}
else
{
num = s.stk[s.top];
printf ("poped element is = %dn", s.stk[s.top]);
s.top = s.top - 1;
}
return(num);
}

/*Function to display the status of the stack*/
void display ()
{
int i;
if (s.top == -1)
{
printf ("Stack is emptyn");
return;
}
else
{
printf ("nThe status of the stack isn");
for (i = s.top; i >= 0; i--)
{
printf ("%dn", s.stk[i]);
}
}
printf ("n");
}
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C program to illustrate the operations of singly linked list.

Data structures using C,
C program to illustrate the operations of singly linked list. Linked list is a data structure in which the objects are arranged in a linear order. Linked List contains group of nodes, in which each node contains two fields, one is data field and another one is the reference field which contains the address of next node. In this program we insert, delete, search, and display the linked list. Read more about C Programming Language .

/***********************************************************
* You can use all the programs on www.c-program-example.com
* for personal and learning purposes. For permissions to use the
* programs for commercial purposes,
* contact info@c-program-example.com
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* and browse!
*
* Happy Coding
***********************************************************/

#include <stdio.h>
#include <stdlib.h>
#include <conio.h>
#include <string.h>
#define MAX 30

struct EMP
{
int empno;
char empName[MAX];
char designation[MAX];
struct EMP *next;
};

/*********************************************************************/
/* Function to insert a node at the front of the linked list. */
/* front: front pointer, id: employee ID, name: employee name */
/* desg: Employee designation */
/* Returns the new front pointer. */
/*********************************************************************/

struct EMP* insert(struct EMP *front, int id, char name[], char desg[])
{
struct EMP *newnode;

newnode = (struct EMP*) malloc(sizeof(struct EMP));

if (newnode == NULL)
{
printf("nAllocation failedn");
exit(2);
}
newnode->empno = id;
strcpy(newnode->empName, name);
strcpy(newnode->designation, desg);
newnode->next = front;
front = newnode;
return(front);
} /*End of insert() */

/* Function to display a node in a linked list */
void printNode(struct EMP *p)
{
printf("nEmployee Details...n");
printf("nEmp No : %d", p->empno);
printf("nName : %s", p->empName);
printf("nDesignation : %sn", p->designation);
printf("-------------------------------------n");
} /*End of printNode() */

/* ********************************************************/
/* Function to deleteNode a node based on employee number */
/* front: front pointer, id: Key value */
/* Returns: the modified list. */
/* ********************************************************/

struct EMP* deleteNode(struct EMP *front, int id)
{
struct EMP *ptr;
struct EMP *bptr; /* bptr is pointing to the node behind ptr */


if (front->empno == id)
{
ptr = front;
printf("nNode deleted:");
printNode(front);
front = front->next;
free(ptr);
return(front);
}

for(ptr=front->next, bptr=front; ptr!=NULL; ptr=ptr->next, bptr=bptr->next)
{
if (ptr->empno == id)
{
printf("nNode deleted:");
printNode(ptr);
bptr->next = ptr->next;
free(ptr);
return(front);
}
}
printf("nEmployee Number %d not found ", id);
return(front);
} /*End of deleteNode() */

/*****************************************************************/
/* Function to search the nodes in a linear fashion based emp ID */
/* front: front pointer, key: key ID. */
/*****************************************************************/
void search(struct EMP *front, int key)
{
struct EMP *ptr;

for (ptr = front; ptr != NULL; ptr = ptr -> next)
{
if (ptr->empno == key)
{
printf("nKey found:");
printNode(ptr);
return;
}
}
printf("nEmployee Number %d not found ", key);
} /*End of search() */

/* Function to display the linked list */
void display(struct EMP *front)
{
struct EMP *ptr;

for (ptr = front; ptr != NULL; ptr = ptr->next)
{
printNode(ptr);
}
} /*End of display() */

/* Function to display the menu of operations on a linked list */
void menu()
{
printf("---------------------------------------------n");
printf("Press 1 to INSERT a node into the list n");
printf("Press 2 to DELETE a node from the list n");
printf("Press 3 to DISPLAY the list n");
printf("Press 4 to SEARCH the list n");
printf("Press 5 to EXIT n");
printf("---------------------------------------------n");
} /*End of menu() */

/* Function to select the option */
char option()
{
char choice;

printf("nn>> Enter your choice: ");
switch(choice=getche())
{
case '1':
case '2':
case '3':
case '4':
case '5': return(choice);
default : printf("nInvalid choice.");
}
return choice;
} /*End of option() */

/* The main() program begins */
void main()
{
struct EMP *linkList;
char name[21], desig[51];
char choice;
int eno;

linkList = NULL;

printf("nWelcome to demonstration of singly linked listn");

menu(); /*Function call */

do {
choice = option(); /*to choose oeration to be performed */

switch(choice)
{
case '1': printf("nEnter the Employee Number : ");
scanf("%d", &eno);

printf("Enter the Employee name : ");
fflush(stdin);
gets(name);

printf("Enter the Employee Designation : ");
gets(desig);

linkList = insert(linkList, eno, name, desig);
break;

case '2': printf("nnEnter the employee number to be deleted: ");
scanf("%d", &eno);

linkList = deleteNode(linkList, eno);
break;

case '3': if (linkList == NULL)
{
printf("nList empty.");
break;
}
display(linkList);
break;

case '4': printf("nnEnter the employee number to be searched: ");
scanf("%d", &eno);

search(linkList, eno);
break;

case '5': break;
}
} while (choice != '5');
} /*End fo main()*/
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C program to find the sparse matrix

C program to accept a matrix and determine whether it is a sparse matrix or not?. A sparse matrix is a matrix, which has more zero elements than nonzero elements. Read more about C Programming Language .

/***********************************************************
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* for personal and learning purposes. For permissions to use the
* programs for commercial purposes,
* contact info@c-program-example.com
* To find more C programs, do visit www.c-program-example.com
* and browse!
*
* Happy Coding
***********************************************************/


#include <stdio.h>

void main ()
{
static int m1[10][10];
int i,j,m,n;
int counter=0;

printf ("Enter the order of the matixn");
scanf ("%d %d",&m,&n);

printf ("Enter the co-efficients of the matixn");
for (i=0;i<m;++i)
{
for (j=0;j<n;++j)
{
scanf ("%d",&m1[i][j]);
if (m1[i][j]==0)
{
++counter;
}
}
}
if (counter>((m*n)/2))
{
printf ("The given matrix is sparse matrix n");
}
else
printf ("The given matrix is not a sparse matrix n");

printf ("There are %d number of zeros",counter);

} /* EN dof main() */
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C Program to find second largest and second smallest element in an array

Arrays in C,
C Program to find second largest and second smallest element in the array.  Program will accept a list of data items and find the second largest and second smallest elements in it. And also compute the average of both. And search for the average value whether it is present in the array or not. Display appropriate message on successful search.  Read more about C Programming Language .

/***********************************************************
* You can use all the programs on  www.c-program-example.com
* for personal and learning purposes. For permissions to use the
* programs for commercial purposes,
* contact info@c-program-example.com
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* 
*                                  Happy Coding
***********************************************************/


#include <stdio.h>

void main ()
{
 int number[30];
 int i,j,a,n,counter,ave;

 printf ("Enter the value of Nn");
 scanf ("%d", &n);

 printf ("Enter the numbers n");
 for (i=0; i<n; ++i)
  scanf ("%d",&number[i]);

 for (i=0; i<n; ++i)
 {
  for (j=i+1; j<n; ++j)
  {
   if (number[i] < number[j])
   {
    a        = number[i];
    number[i] = number[j];
    number[j] = a;
   }
  }
 }

 printf ("The numbers arranged in descending order are given belown");
 for (i=0; i<n; ++i)
 {
  printf ("%dn",number[i]);
 }

 printf ("The 2nd largest number is  = %dn", number[1]);
 printf ("The 2nd smallest number is = %dn", number[n-2]);

 ave = (number[1] +number[n-2])/2;
 counter = 0;

 for (i=0; i<n; ++i)
 {
  if (ave == number[i])
  {
   ++counter;
  }
 }
 if (counter == 0 )
  printf ("The average of %d  and %d is = %d is not in the arrayn", number[1], number[n-2], ave);
 else
  printf ("The average of %d  and %d in the array is %d in numbersn",number[1], number[n-2], counter);
}           /* End of main() */
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C Program to multiply given number by 4 using bitwise operators

C Program to multiply given number by 4 using bitwise operators. Bitwise operators allows to cahnge or edit the specific bits within an integer. Program will multiply a given number by 4 using left shift(<<) bitwise operator. Read more about C Programming Language .

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* programs for commercial purposes,
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* and browse!
*
* Happy Coding
***********************************************************/

/* c program to multiply given number by 4 *
* using bitwise operators */

#include <stdio.h>

void main()
{
long number, tempnum;

printf("Enter an integern");
scanf("%ld",&number);
tempnum = number;
number = number << 2; /*left shift by two bits*/

printf("%ld x 4 = %ldn", tempnum,number);
}
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C Program To Compute X ^ N

C program to compute the value of X ^ N, given X and N as inputs. Program accepts two integers x, n and computes the power of x to the n by using recursion function power().  Read more about C Programming Language .

/***********************************************************
* You can use all the programs on www.c-program-example.com
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* programs for commercial purposes,
* contact info@c-program-example.com
* To find more C programs, do visit www.c-program-example.com
* and browse!
*
* Happy Coding
***********************************************************/


#include <stdio.h>
#include <math.h>

void main()
{
long int x,n,xpown;
long int power(int x, int n);

printf("Enter the values of X and Nn");
scanf("%ld %ld",&x,&n);

xpown = power (x,n);

printf(" %d to the power %d = %ldn",x,n,xpown);
}

/*Recursive function to computer the X to power N*/

long int power(int x, int n)
{
if (n==1)
return(x);
else if ( n%2 == 0)
return (pow(power(x,n/2),2)); /*if n is even*/
else
return (x*power(x, n-1)); /* if n is odd*/
}
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