What the!?

[clover leaf]

I just found a program that I don't remember making so I compiled to see what it is. I still don't know what it is anyone know?

#include <iostream>
using namespace std;
int main ()
{
int a,b;
cin >>a,b=a%50;
cout <<b;
cin >>a;
return 0;
}

[buffbill]

a and b not initialized... bad
l 6 is not valid
prog==junk

[guestgulkan]

Line 6 is valid

[helios]

The program is both valid and correct. It just doesn't look that way.

[Rabtherab]

Well, the program asks for an integer input, then assigns the modulus (remainder) of a/50 to b.
Then it prints out the value of b and waits for you to input a new value for a, then exits without doing anything else.

Lets say you put in a value of 127 to be assigned to a, now if you do 127/50 the answer is 2 and the remainder is 27. So it will print out 27.

Let's say you enter a value of 20. 20/50 = 0 with a remainder of 20.

If you commented your code or output something a little more meaningful with your cout statements you'd be able to understand it better.

For example:

// This program will accept an integer value and assign it to iDividend,
// then the program will perform a modulus division of iDividend / DIVISOR and assign
// the result to iRemainder.  Next output the quotient and remainder then
// wait for the user to press a key before exiting the program.

#include <iostream>
#include <conio.h>

using namespace std;

int main(int argc, char** argv) {
	// declare a long variable iDividend, and a short variable Remainder, and
        // assign them a value of zero, so that they begin life from a known state.
        // Otherwise there's no telling what kind of junk they could be holding
        // It just depends on what was laying around in that memory space
        // when you ran your program.
	long iDividend = 0;
        short iRemainder = 0; // will never be larger than 49 so a short is enough

        // You could also declare those longs as shorts if memory is a
        // concern, but longs will handle a larger range of values and is
        // usually worth the extra memory.

        // Also, you may as well define a const short as your DIVISOR, rather than
        // use a literal number.
	const short DIVISOR = 50;  // a short is all the space we need here since this
                                                    // number will not change.

        // Why not use ints?

        // shorts are guaranteed to be 2 bytes
        // in size, whereas longs are 4 bytes in size.
        // and ints can be 2 or 4, there is no guarantee.

        // So to make sure you don't get caught by any gotchas
        // use shorts and longs rather than ints, then you know
        // what kind of memory your variables are consuming.

        // To make sure we are speaking the same language..
        // In division we use these terms to describe each of
        // the components:

	// a / b = c  where a is the Dividend, b is the Divisor,
        // and c is the Quotient

	// assign the value to iDividend ('a' renamed),
        // assign iRemainder ('b' renamed) to the
	// result of iDividend % DIVISOR
        // % is the modulus operator and what it means is
        // give me the remainder when dividing the two numbers.
        // such as 10 % 3

        // In this case 10 / 3 = 3 with a remainder of 1
        // so 10 % 3 = 1.  Cool huh?
	cout << "Enter an integer (whole number): ";
	cin >> iDividend, iRemainder = iDividend % DIVISOR;

	// output a meaningful response
	cout << iDividend << " / " << DIVISOR << " = " << iDividend / DIVISOR << ", R = "
                << iRemainder << endl;

	// wait for the user to enter a value
	cout << "Press any key to exit...";

	// ignore any newline already buffered
	cin.ignore(0,'\n');

	// get the key press
	getch();

	// and exit (0 indicates success)
	return 0;
}

This produces the following output:

Enter an integer (whole number): 723
723 / 50 = 14, R = 23
Press any key to exit...
Process returned 0 (0x0) execution time : 32.702 s
Press any key to continue.

I hope this helps you out. It's way more commented than you normally would, but I wanted to be sure you understood what was going on.

Also, you would normally do some error checking to make sure the input is valid, such a checking that the value entered is in fact an integer and not a float, for example.

Edit: A good supply of comments, variable names that describe their purpose, proper indentation, and some white-space will go a long way toward making your source code more readable.