#include <stdio.h>
#include <stdlib.h>

/* run this program using the console pauser or add your own getch, system("pause") or input loop */
/**
Cau truc function
datatype ten_ham(datatype param1, ...) {
	//source code
}
*/

void showMessage() {
	printf("\nXin chao A");
	printf("\nXin chao B");
	printf("\nXin chao C");
	printf("\nXin chao D");
	printf("\nXin chao E");
}

void tinhtong(int n) {
	int i, sum;
	
	//Tinh tong cac so nguyen tu 0 -> n
	sum = 0;
	for(i=0;i<=n;i++) {
		sum+=i;
	}
	printf("\nsum = %d", sum);
}

int tinhtong4(int n) {
	int i, sum;
	
	//Tinh tong cac so nguyen tu 0 -> n
	sum = 0;
	for(i=0;i<=n;i++) {
		sum+=i;
	}
	return sum;
}

void tinhtong2(int x, int y) {
	int i, sum;
	
	sum = 0;
	for(i=x;i<=y;i++) {
		sum+=i;
	}
	printf("\nsum = %d", sum);
}

int tinhtong3(int x, int y) {
	int i, sum;
	
	sum = 0;
	for(i=x;i<=y;i++) {
		sum+=i;
	}
	return sum;
}

void changeValue(int x) {
	x++;
	printf("\nx = %d", x);
}

int main(int argc, char *argv[]) {
	//Tim hieu function
//	showMessage();
	
//	int x;
//	printf("\nNhap x = ");
//	scanf("%d", &x);
	
//	showMessage();
//	
//	showMessage();
//	
//	showMessage();
//	
//	showMessage();
//	
//	showMessage();
	
	int i, sum;
	
	/**
	//Tinh tong cac so nguyen tu 0 -> 10
	sum = 0;
	for(i=0;i<=10;i++) {
		sum+=i;
	}
	printf("\nsum = %d", sum);
	*/
	tinhtong(10);

	//Tinh tong cac so nguyen tu 0 -> 25
	/**
	sum = 0;
	for(i=0;i<=25;i++) {
		sum+=i;
	}
	printf("\nsum = %d", sum);
	*/
	tinhtong(25);

	//Tinh tong cac so nguyen tu 0 -> 100
	/**
	sum = 0;
	for(i=0;i<=100;i++) {
		sum+=i;
	}
	printf("\nsum = %d", sum);
	*/
	tinhtong(100);
	
	//Tinh tong cac so nguyen tu 15-50
	/**sum = 0;
	for(i=15;i<=50;i++) {
		sum+=i;
	}
	printf("\nsum = %d", sum);
	*/
	tinhtong2(15, 50);//Luu duoc ket qua 15-50 => vao 1 bien s1
	
	//Tinh tong cac so nguyen tu 25-60
	/**
	sum = 0;
	for(i=25;i<=60;i++) {
		sum+=i;
	}
	printf("\nsum = %d", sum);
	*/
	tinhtong2(25, 60);//Luu duoc ket qua 25-60 => vao 1 bien s2
	
	//So sanh ket qua tong cua 15 -> 50 va 25 -> 60.
	//Tong 15-50 > 25-60
	//Tong 15-50 < 25-60
	//Tong 15-50 = 25-60
	int s1 = tinhtong3(15, 50);
	int s2 = tinhtong3(25, 60);
	if(s1 > s2) {
		printf("\nTong 15-50 > 25-60");
	} else if(s1 < s2) {
		printf("\nTong 15-50 < 25-60");
	} else {
		printf("\nTong 15-50 = 25-60");
	}
	
	//Huong dan phan biet bien trong function.
	int x = 5;
	printf("\nx = %d", x);
	changeValue(x);
	printf("\nx = %d", x);
	
	return 0;
}