calculator with using function and for loop

[alitt]

hi guys
i'm gonna make a calculator and just add 5 numbers,i wanna using for loops for getting 5 number but i have problem

 
#include <iostream>
using namespace std;

int num,i;
void getnumber();
int sum();

int main(){
	
	int m;
	m=sum();

        cout<<m;
	
	return 0;
}

void getnumber(){
	
	for(i=1;i<=5;i++)
	
	cout<<"enter number: ";
	cin>>num;
}

int sum(){
	
	int sumi;
	sumi+=i;
	return(sumi);
	
}

[ephraimr]

Hey there.
Lets start from main.
According to your program, m is a return value of sum [sumi]
What does sum do? Adds i to it. What is i? Nothing, just has a garbage default value in it.
Remember that i is just used to run through the loop. i is not the value of what you entered!
You did not call getnumber() anywhere so it never touches that. :D
In getmain, think of m as a box in memory.
Suppose I enter
1
2
3
4
5
It first takes 1 and puts it into m. Then it removes 1 and puts 2 into the box etc.

I would suggest learning from a good book :)
Here is a way :

#include <iostream>
using namespace std;
int main() {
cout << "Enter numbers";
int n,sum = 0;
for(int i = 0; i < 5; i++){
cin >> n;
sum+=n;
}
cout << "Thats " << sum << " when added!";
return 0;
}

[yash8087]

you are not calling the function getnumber() in the function main() so,this will not work
try this code:


#include <iostream>
using namespace std;


void getnumber();
int main(){

getnumber();
return 0;
}

void getnumber(){ int sumi=0;
int num[5];//declare an array of five numbers
cout<<"enter number: ";

for(int i=0;i<5;i++)//accept five numbers
{cin>>num[i];
sumi=sumi+num[i];} //for addition of all inputed numbers
cout<<sumi;;

}

[AbstractionAnon]

i have problem

What problem?

A few obvious problems:

line 23: Only this line is within range of the for statement. If you want to include multiple statements, use {}

	for (i=1;i<=5;i++)
	{  cout<<"enter number: ";
	    cin>>num;
        }

Note that the above code will overlay num for each iteration of the loop.
Line 19: You never call getnumber().

Line 29: sumi is an uninitialized variable (garbage).

Line 30: You're adding i to sumi. i is the index to your for loop, not a value you want to sum.

[alitt]

thanks ephraimr, yash8087, AbstractionAnon
i understood
really thanks for help

[ephraimr]

alitt, check a c++ book, such as programming principles and practice using c++

[alitt]

sure
thanks a lot

[alitt]

excuse me guys
i have a new problem
i don't know why answer is wrong

#include <iostream>
using namespace std;

int num;
void getnumber();
int sum();


int main(){
	
	getnumber();
	int m;
	m=sum();
	cout<<m;
	
	
	
	return 0;
}

void getnumber(){
	
	for(int i=1;i<=3;i++){
		
		cout<<"enter number: ";
		cin>>num;
	}
	
}

int sum(){
	
	int sumi;
	sumi+=num;
	return(sumi);
	
	
}  

[alitt]

i used array and changed to this but doesn't work

#include <iostream>
using namespace std;

int num[5],i;
void getnumber();
int sum();


int main(){
	
	getnumber();
	int m;
	m=sum();
	cout<<m;
	
	
	
	return 0;
}

void getnumber(){
	
	for(i=1;i<=5;i++){
		
		cout<<"enter number: ";
		cin>>num[i];
	}
	
}

int sum(){
	
	int sumi;
	sumi+=num[i];
	return(sumi);
	
}

[ephraimr]

int sum(){
	
	int sumi;
	sumi+=num[i];
	return(sumi);
	
}

should be

int sum(){
	
	int sumi = 0;
        for(int i =0; i < 5; i ++)
	sumi+=num[i];
	return(sumi);
	
}

because, you have to go through the array elements
and

void getnumber(){
	
	for(i=1;i<=5;i++){
		
		cout<<"enter number: ";
		cin>>num[i];
	}
	
}

should be

void getnumber(){
	
	for(i=0;i<5;i++){
		
		cout<<"enter number: ";
		cin>>num[i];
	}
	
}

because, in an array in c++, the "boxes" are numbered from 0 to n-1
int a[5] creates an array with the boxes a[0] a[1] a[2] a[3] a[4] in it

[cire]

The variable sumi is not initialized to any value in either alitt's code or ephraimr's code, so it contains junk.

Junk + some values is still junk.

[alitt]

ephraimr really thanks

[alitt]

another question
i don't why sum doesn't work

#include <iostream>
#include <conio.h>
using namespace std;

int num[5],counter=0;
void getnumber();
int sum();
void print();

int main(){
	
	char op;
	
	while(1){
		
		system("cls");
		
		cout<<"1- input 2- sum 3- print \n";
		cin>>op;
		
		switch(op){
			case '1':{
				getnumber();
				break;
			}
			case '2':{
				int total;
				total=sum();
				cout<<total;
				break;
			}
			case '3':{
				print();
				break;
			}
			
			
		}
		
	}
	return 0;
}
void getnumber(){
	
	cout<<"enter number: ";
	cin>>num[counter];
	counter++;
}
int sum(){
	
	int sumi=0;
	for(int i=0;i<counter;i++)
		sumi+=num[i];
		return(sumi);
}
void print(){
	system("cls");
	for(int i=0;i<=counter;i++){
		cout<<num[i]<<endl;
	}
	getch();	
}

[AbstractionAnon]

Several problems with your program.

1) getnumber has no protection against entering more than 5 numbers. Doing so will write past the end of num[].

2) Globals should be avoided.

3) print is going to print out too many numbers. Line 58 should be i<counter, not <=.

[alitt]

thanks
i made array[5] but i'd like to add 2 or 3 numbers when i call sum
i wont insert 5 numbers to add,maybe id like to insert 4 numbers
thanks again

[alitt]

you're right
getnumber is not protect against more 5 number
how should i write getnumber?

[AbstractionAnon]

A simple if statement and return is all you need.

static const int MAXNUM = 5;
int num[MAXNUM];

void getnumber()
{   if (counter >= MAXNUM)
     {  cout << "Array is full" << endl;
         return;
     }
	cout<<"enter number: ";
	cin>>num[counter];
	counter++;
}

Note that I've made MAXNUM a constant. By using MAXNUM, instead of the hard coded value 5, if you ever want to change the size of the array, all you have to do is change that one line.

[alitt]

thank you so much
my problem has solved