program to print/display 2,4,6,8,10,12... to 15th term.

//program to print/display 2,4,6,8,10,12... to 15th term.

#include<stdio.h>
#include<conio.h>
void main()
{
int k=2;

while(k<=15)
   {
      printf("%d,",k);
      k=k+2;
   }
getch();
}

Or
you can use following method.

first term(a)=2
common difference(d)=2
number of terms(n)=15
here  we can see that given series is in arithmetic progression so nth term=a+(n-1)*d.It gives us nth term=30 i.e.
last term will be 30.
We put 30 in while loop

//program to print/display 2,4,6,8,10,12... to 15th term.
#include<stdio.h>
#include<conio.h>
void main()
{
int k=2;

while(k<=30)
   {
      printf("%d,",k);
      k=k+2;
   }
getch();
}

program to print/display 1,8,27... to 10th term.

//program to print/display 1,8,27... to 10th term.
#include<stdio.h>
#include<conio.h>
void main()
{
int k=1,n;

while(k<=10)
   {
      printf("%d,",k*k*k);
      k++;
   }
getch();
}

second method:
//program to print/display 1,8,27... to 10th term.
#include<stdio.h>
#include<conio.h>
#include<math.h>void main()
{
int k=1,n;

while(k<=10)
   {
      printf("%d,",pow(k,3);// it means get power 3 of k. pow() is  a function stored in 'math.h'
      k++;
   }
getch();
}


note:
If you want to display 'n' number of times then simply put
  int n;declare this.
printf("enter value of n\n");
scanf("%d",&n) 
put above two lines before while loop.

program to input your name and address and to display them 40 times.

//program  to input your name and address and to display them 40 times.
#include<stdio.h>
#include<conio.h>
void main()
{
char name[40],address[40];
int k=0;printf("enter your name\n");
gets(name);
printf("enter your address");
gets(address);
while(k<=40)
   {
      puts(name);
      puts(address);
      k++;
   }
getch();
}

note:
1)
     you can also use printf(  ) instead 'puts'.(without single quote)   and scanf("%^[\n]",name) instead 'gets' function.
2)
   If you want to display 'n' number of times then enter value of 'n' with its declaration.

program to print/display 100 to 1 natural numbers.

//program  to print/display 100 to 1 natural numbers.
#include<stdio.h>
#include<conio.h>
void main()
{
int k=100;
while(k>=1)
   {
      
       printf("%d,",k);
      
    k--;
   }
getch();
}

note:
If you want to display numbers from 'n' to 1 then
   input 'n' and keep all others same.