series

#include <stdio.h>

int main()
{

float a1, d, sum;
int num, code , i;

printf("Enter rhe first element (real), the difference (real) and the number of elements:");

do {
       scanf("%f%f%d", &a1,&d, &num);
    if (scanf("%f%f%d", &a1,&d, &num)==1)
       break;
    else
         printf("iilegal input, try agian");

   } while(1);


do  {
 printf("Enter a code for desired operation from the menu :\n   1-display an aritmetic progression\n   2-display an aritmetic series\n    3 -display a geometric progression\n   4-display a  geometric series\n    5 - exit the program\n");

  scanf("%d", &code);
   if (code==1) {
    for(i=0; i<num; i++)
       printf("%f" ,a1+i*d);
            }

         else  if (code==2) {
               sum=0;
                for(i=0; i<num; i++)
                sum+= a1+i*d;
                printf("%f", sum);
                       }

                   else  if (code==3) {
                    printf("%f" ,a1);
                      for (i=1; i<num; i++)
                       printf("%f" ,a1*=d);
                      }

                              else if (code==4) {
                              sum=a1;
                                for (i=1; i<num; i++) {
                                 a1*=d;
                                 sum+= a1;  }
                                 printf("%f", sum);
                             }

                                        else if (code==5){
                                         printf("bye");
                                         break; }

                                            else
                                             printf("iilegal input, try agian");


   } while (1);


 retuern 0;
}