Lab 1-Algorithm Function- designing and implementing algorithms using C program

/*
Title: Lab #1: Algorithm, Function
Objective: Create a program with one main that solves 5 different problems using non-recursive method 
including Summation: (Σ1+2+3+...+n), factorial(n), fibonacci(n), gcd(x,y) and power(a,b) by calling a
 function using a menu.
*/

//Includes
#include <stdio.h>  //C-Preprocessor Directives

//Function Prototypes
int summation(int n); // The sum of n and all the integer numbers below it down to 0
int factorial(int n); // The product of n and all the integer numbers below it down to 1
int fibonacci(int n); // Fibonacci(n) returns the nth Fibonacci number.
int gcd(int x,int y); // The greatest common denominator of the of the two integers numbers
int power(int a,int b); //Integer a raised to the power of integer b

//Main function
int main(void){

    int choice=0;
	//Main loop
    do{
		// Display the menu choices to the user and prompt for input.
        printf("1- Use the SUMMATION with non-recursive iteration\n");
        printf("2- Use the FACTORIAL with non-recursive iteration\n");
        printf("3- Use the FIBONACCI with non-recursive iteration\n");
        printf("4- Use the GCD with non-recursive iteration\n");
        printf("5- Use the POWER with non-recursive iteration\n");
        printf("0- Quit\n");
        scanf("%d", &choice);

    switch(choice){
        case 1:{
			// Collect information and call summation(n) function.
            int n,result;
            printf("Please enter a value of n \n");
            scanf("%d",&n);
	           if(n<1){
                  printf("\nError, Please enter a number greater than or equal to 1\n\n");
                  continue;
            }
            else{
                 result=summation(n);
                 printf("\nResult is %d \n\n", result);
                 break;}
        }
        case 2:{
			// Collect information and call factorial(n) function.
            int n,result;
            printf("Please enter a value of n \n");
            scanf("%d",&n);
            if(n<0){
                  printf("\nError, Please enter a number greater than or equal to 0\n\n");
                  continue;
            }
            else{
            	 result=factorial(n);
                 printf("\nResult is %d \n\n", result);
                 break;
            }
        }
        case 3:{
			// Collect information and call fibonacci(n) function.
            int n,result;
            printf("Please enter a value of n \n");
            scanf("%d",&n);
            if(n<0){
                  printf("\nError, Please enter a number greater than or equal to 0\n\n");
                  continue;
            }
            else{
                 result=fibonacci(n);
                 printf("\nResult is %d \n\n", result);
                 break;
            }
        }
        case 4:{
			// Collect information and call gcd(x,y) function.
            int x,y,result;
            printf("Please enter a value for the first Number and then Enter a value for the Second Number \n");
            scanf("%d %d",&x,&y);
            if(x<0 || y<0){
                  printf("\nError, Please enter a number greater than or equal to 0\n\n");
                  continue;
            }
            else{
                  result=gcd(x,y);
                  printf("\nResult is %d \n\n", result);
                  break;
            }
        }
        case 5:{
			// Collect information and call power(x,y) function.
            int x,y,result;
            printf("Please enter a value for the first Number and then Enter a value for the Second Number \n");
            scanf("%d %d",&x,&y);
            if(x<0 || y<0){
                  printf("\nError, Please enter a number greater than or equal to 0\n\n");
                  continue;
            }
            else{
                  result=power(x,y);
                  printf("\nResult is %d \n\n", result);
                  break;
            }
        }
        case 0:{
			// Display  a message for user after pressing 0 to Quit the program.
            printf("\nThank you for using this program, Please come back again \n\n\n");
            break;
        }
        default:{
			// Display  a message for user after pressing a number other than 0,1,2,3,4 and 5.
            printf("\nIncorrect input, please choose a number between 1 and 5,or press 0 to Quit \n\n\n");
            break;
        }
    }
    }while (choice !=0); // End the while loop if the choice was 0
    return 0; //exit main
}// end of main

/*
	Objective: Compute the sum of n + all the numbers below it to 1
	input: A positive integer that is 1 and higher
	output: The sum of n plus all integer numbers down to 1, example: ∑ n +(n-1) +...+ 4+ 3+ 2+ 1
*/
int summation(int n){
    int total=0,i;
    for (i = 1;i <=n;i++){
        total += i;
    }
    return total;
}

/*
	Objective: Compute the factorial for integer n
	input: A positive integer that is 1 and higher (Non-negative integer)
	output: Return the factorial for integer n example: n*(n-1)*...* 4*3*2*1
*/
int factorial(int n){
   int i;
   int total = 1;
   for (i = 1; i <= n; i++){
      total *= i;
   }
   return total;
}

/*
	Objective: Compute the nth Fibonacci number.
	input: A positive integer that is 1 and higher
	output: Compute the nth Fibonacci number which is determined by adding the last two Fibonacci numbers together,
	example: (to find the third Fibonacci number we add the two previous numbers in the sequence 0,1,1 which is 1+1=2)
*/
int fibonacci(int n)
{
	int i, k = 0, j = 1, fib = 1;
	for (i = 1; i < n; i++){
		fib = k + j;
		k = j;
 		j = fib;
	}
	return fib;
}

/*
	Objective: Compute the greatest common denominator of the of the two integers numbers x and y
	input: x , y are integers and y is greater than 0
	output: Return the greatest common denominator of the of the two integer numbers x,y
			such that(gcd(x,y)=gcd(y,x MOD y), if y>0 and gcd(x,y)=x, if y=0)
*/
int gcd(int x, int y){
	int temp;
	while (y > 0){
		temp = x;
		x = y;
		y = temp%y;
	}
	return x;
}

/*
	Objective: Compute a raised to the power of b
	input: Two positive integer a and b
	output: return a raised to the power of b. (example for a = 3, b = 3 then power(3,3)= a*a*a = 3*3*3=27).
*/
int power(int a, int b){
	int power = 1, i;
	for (i = 0; i < b; i++){
		power *= a;
	}
	return power;
}