#include<stdio.h>
int main(){
    int k,r;
    long int i=0,j=1,f;
    long int sum = 1;

    printf("Enter the number range: ");
    scanf("%d",&r);

    for(k=2;k<r;k++){
         f=i+j;
         i=j;
         j=f;
         sum = sum + j;
    }

    printf("Sum of Fibonacci series is: %ld",sum);
  
    return 0;
}
Sample output:
Enter the number range: 4
Sum of Fibonacci series is: 4

#include<stdio.h>
int main(){
  int i=1,f=1,num;

  printf("Enter a number: ");
  scanf("%d",&num);

  while(i<=num){
      f=f*i;
      i++;
  }

  printf("Factorial of %d is: %d",num,f);
  return 0;
}
Sample output:
Enter a number: 5
Factorial of 5 is: 120

#include<stdio.h>
int main(){
  int i,f=1,num;

  printf("Enter a number: ");
  scanf("%d",&num);

  for(i=1;i<=num;i++)
      f=f*i;

  printf("Factorial of %d is: %d",num,f);
  return 0;
}

#include<stdio.h>

void findFactorial(int,int *);
int main(){
  int i,factorial,num;

  printf("Enter a number: ");
  scanf("%d",&num);

  findFactorial(num,&factorial);
  printf("Factorial of %d is: %d",num,*factorial);

  return 0;
}

void findFactorial(int num,int *factorial){
    int i;

    *factorial =1;

    for(i=1;i<=num;i++)
      *factorial=*factorial*i;
}

#include<stdio.h>

int findFactorial(int);
int main(){
  int i,factorial,num;

  printf("Enter a number: ");
  scanf("%d",&num);

  factorial = findFactorial(num);
  printf("Factorial of %d is: %d",num,factorial);

  return 0;
}

int findFactorial(int num){
    int i,f=1;

    for(i=1;i<=num;i++)
      f=f*i;

     return f;
}
Sample output:
Enter a number: 8
Factorial of 8 is: 40320