NEB30:Difference between struct and union

Ans:-
The differences between struct and union are given below in tabular form.
                   

struct	Union
1.It stores dis-similar data.Each gets separate space in memory.They do not share memory	1. It stores dis-similar type of data.Total memory space is equal to the member with largest size.They share memory space.
2.we can access member in any sequence .	2.We can access that whose value is recently used.
3.It uses keyword 'struct'	3.It uses keyword 'union'
4.We can initialize values of member/s and in any order	4.We can initialize that member which is first declared.
5.It consumes more memory	5.It consumes less memory.
6.Its syntax     struct tag { datatype member1; datatype member2; datatype member3; }variable;	6.Its syntax     union tag { datatype member1; datatype member2; datatype member3; }variable;
Example struct student { int roll; char sex; float percentage; }var;	Example union student { int roll; char sex; float percentage; }var;

NEB27:program to get factorial value of a number using recursion

//program to get factorial value of a number using recursion
#include <stdio.h>
#include <stdlib.h>
int recur(int n);
int main()
{
 int n;
 printf("ente a number\n");
 scanf("%d",&n);
printf("the factorial value is\n");
printf("%d",recur(n));
getch();
return 0;
}
int recur(int n)
{
 if(n<=0)
  {
          return 1;
}
else
{
    return n*recur(n-1);
}

}

NEB29:Difference between array and struct

Ans:-
Differences between array and struct are given below.                                                                                                                                                

Array	struct
1.It stores same type of data	1. It stores dis-similar type of data.
2.It uses static memory allocation .	2.I uses dynamic memory allocation.
3.It takes less time to access elements.	3.It takes more time to access elements.
4.It uses index value to access elements.	4.It takes help of period operator(.) to access elements.
5.It is derived data type.	5. IT is user's defined data type.
6.We can not define array of array.	6.We can define array of structure.
7.Its syntax is                                           data type identifier[value]; example,int a[20];	7.Its syntax is struct tag {datatype member1; datatype member2; data type member3; }variable; example, struct det {char name[100]; char add[40]; int  roll; }variable;

program to know a matrix is identity or not

// program to know a matrix is identity or not
//to know a matrix is identity or not
#include<stdio.h>
#include<conio.h>
void main()
{
clrscr();
int a[5][5],order,i,j,first=0,second=0;
printf("enter order\n");
scanf("%d",&order);
printf("enter matrix elements\n");
for(i=0;i<order;i++)
  {
    for(j=0;j<order;j++)
      {
       scanf("%d",&a[i][j]);
      }
  }
printf("the matrix is\n");
for(i=0;i<order;i++)
  {
    for(j=0;j<order;j++)
      {
       printf("%d",a[i][j]);
      }
    printf("\n");

  }
 for(i=0;i<order;i++)
  {
    for(j=0;j<order;j++)
      {
       if(i==j)
       {
first=first+1;
}
else
{
second=second+a[i][j];
}

  }
  }

  if(first==order && second==0)
  {
  printf("it is identity matrix\n");
  }
  else
  {
  printf("it is not");
  }

  getch();
  }

program to understand strcmp(), libraray function

//program to understand strcmp(), libraray function
//strcmp() function
#include<stdio.h>
#include<conio.h>
#include<string.h>
void main()
{
clrscr();
char first[50],sec[50];
int k;
gets(first);
gets(sec);
k=strcmp(first,sec);
printf("k=%d",k);
if(k==0)
  {
    printf("both are same");
    }
else if(k>0)
  {
  printf("first string =%s has more value\n",first);
  }
  else if(k<0)
  {
  printf("second string =%s has more value\n",sec);
  }
  getch();
  }

program to get hcf and lcm of two numbers

//program to get hcf and lcm of two numbers
#include<stdio.h>
#include<conio.h>
void main()
{
int a,b,n,n1,lcm,hcf;
printf("enter numbrs\n");
scanf("%d%d",&a,&b);
if(a>b)
{
n=a;
}
else
{
n=b;
}
for(n1=n;n1>=1;n1--)
    {
    if(a%n1==0 && b%n1==0)
     {
     hcf=n1;
     break;
     }
}
printf("hcf=%d",hcf);
printf("lcm=%d",(a*b)/hcf);
getch();
}

program to multiply two matrices of order mxn

// program to multiply two matrices of order 'mxn'
#include <stdio.h>
#include<conio.h>
void main()
{
    int A[3][3], B[3][3], C[3][3];
    int row, col, i, sum;

    /*
     * Reads elements in first matrix from user
     */
    printf("Enter elements in matrix A of size 2x2: \n");
    for(row=0; row<2; row++)
    {
for(col=0; col<2; col++)
{
   scanf("%d", &A[row][col]);
}
    }

    /*
     * Reads elements in second matrix from user
     */
    printf("\nEnter elements in matrix B of size 2x2: \n");
    for(row=0; row<2; row++)
    {
for(col=0; col<2; col++)
{
   scanf("%d", &B[row][col]);
}
    }

    /*
     * Multiplies both matrices A*B
     */
    for(row=0; row<2; row++)
    {
for(col=0; col<2; col++)
{
   sum = 0;
   /*
    * Multiplies row of first matrix to column of second matrix
    * And stores the sum of product of elements in sum.
    */
   for(i=0; i<2; i++)
   {
sum += A[row][i] * B[i][col];
   }

   C[row][col] = sum;
}
    }

    /*
     * Prints the product of matrices
     */
    printf("\nProduct of Matrix A * B = \n");
    for(row=0; row<2; row++)
    {
for(col=0; col<2; col++)
{
   printf("%d ", C[row][col]);
}
printf("\n");
    }
getch();;
}