search prime number

Q. Write a C program to find whether a number is prime or not.

Definition of prime number:A prime number is one,which is divisible only by one or itself. And its must greater than 1.

And if number is not prime, it is called composite number and vice versa.

Ans.

#include<stdio.h>

#include<stdio.h>

int main()

{

 int x,num;

 printf("Enter number : ");

 scanf("%d",&num);

 x=2;

 while(x<=num-1)

 {

   if(num%x==0)

   {

      printf("Number is not prime!!");

      break;

   }

   x++;

 }

 if(x==num)

    printf("Number is prime!!");
 getch();

 return 0;

}

    output of above program :

Enter number : 7

Number is prime!!

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Example of Array

Q. Write a C program to read the internal test marks of 25 students in a class and show the number of students who have scored more than 50% in the test.

Ans.

/*We assume that maximum marks in internal test is 500. */
#include<stdio.h>

#include<conio.h>
#define SIZE 5

int main()

{

 int arr[SIZE];

 int i,j,max=0,min=0;

 for(i=1; i<=SIZE; i++)

 {

   printf("Enter %d student marks : ",i);

   scanf("%d",&arr[i]);

 }

 for(i=1; i<=SIZE; i++)

 {

  if(arr[i]/5 > 50)

  {

    max++;

    printf("\nMarks which scored more than 50%% is %d",arr[i]);

  }

  else

  {

    min++;

    printf("\nMarks which scored less than 50%% is %d",arr[i]);

  }

 } 
 printf("\n");

 printf("\nTotal number of students who scored more  than 50%% = %d",max);

 printf("\nTotal number of students who scored less than 50%% = %d",min);
 getch();
 return 0;

}

      Output of the above program :

Enter 1 student marks : 450

Enter 2 student marks : 152

Enter 3 student marks : 266

Enter 4 student marks : 65

Enter 5 student marks : 123

Marks which scored more than 50% is 450
Marks which scored less than 50% is 152
Marks which scored more than 50% is 266
Marks which scored less than 50% is 65
Marks which scored less than 50% is 123

Total number of students who scored more than 50% =  2 

Total number of students who scored less than 50% =  3 

Star (*) Praymid

Q. Write a C program to print the following triangle:

					*
				*	*	*
			*	*	*	*	*
		*	*	*	*	*	*	*
	*	*	*	*	*	*	*	*	*
*	*	*	*	*	*	*	*	*	*	*

Ans.

 /*c program for star pyramid*/
 #include<stdio.h>
 #include<conio.h>
 int main()
 {
  int num=6,r,c,sp;
  for(r=1; num>=r; r++)
  {
   for(sp=num-r; sp>=1; sp--)
       printf(" ");
   for(c=r; c>=1; c--)
        printf("*");
   for(c=r; c>1; c--)
        printf("*");
   printf("\n");
  }
  getch();

  return 0; 

 }


/***************OUTPUT***************

					*
				*	*	*
			*	*	*	*	*
		*	*	*	*	*	*	*
	*	*	*	*	*	*	*	*	*
*	*	*	*	*	*	*	*	*	*	*

***************************************/