C++ Tutorials - Absolute n00b spoonfeed

This program will run with no errors but will not do what it is suppose to do.

Objective is:


User will input a number between 1 and 5.

Whatever the number is the computer prints out "You have chosen number ... "

Here is the code:

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#include "stdafx.h"
#include <iostream>
using namespace std;


int main()
{
   int a;
   cout << "Please input a number 1-5" << endl;
   cin >> a;

   switch(a)
   {
   case 1: cout << "You chose 1" << endl;
   case 2: cout << "You chose 2" << endl;
   case 3: cout << "You chose 3" << endl;
   case 4: cout << "You chose 4" << endl;
   case 5: cout << "You chose 5" << endl;
   }
   return 0;
}



See if you can spot the error without running it first. Then if you cannot do that. Run it and it should be clear to you.

dude you have actually taught me something i didnt know here... but i wont give it away till i see some user answers

i think ill need to update a video based on this

thou shalt know this and taketh this to heart; never underestimate the complexity of a line -let alone a snippet- of c++ code. You think what you are seeing here is just some any-day c++ code involving a switch statement? think again!

You need to add to the switch :

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default : cout << "You chose " << a << endl;

So it can cater for values above 5.

I think you need to add

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break;

after each case; otherwise the compiler will automatically say the user has chosen the other numbers as well.

Finished code:

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#include "stdafx.h"
#include <iostream>
using namespace std;


int main()
{
   int a;
   cout << "Please input a number 1-5" << endl;
   cin >> a;

   switch(a)
   {
   case 1: cout << "You chose 1" << endl;
      break;
   case 2: cout << "You chose 2" << endl;
      break;
   case 3: cout << "You chose 3" << endl;
      break;
   case 4: cout << "You chose 4" << endl;
      break;
   case 5: cout << "You chose 5" << endl;
      break;
   }

   char q;
   cin >> q;
   return 0;
}


Thanks for this example. I learned switchs and breaks

Woops, I'm wrong xD

Both of you are correct.

Only the problem is that asib, It's not 100% necessary to have a default switch although it is recommended.


But yesss... Without the break the compiler will not stop after the first switch statement. It will just run through all of them after the one you entered.

Great Job.

The break statement is not only useful. It is absolutely necessary in this situation.

what i didn't know is that switch statements will execute ALL and EVERY case after the first matching case, regardless if the case really matches the tested switch object or not. I thought it will execute all cases that match the condition ONLY if they actually DO match the tested switch object (which may be more than one case).

Quote from the standard (section 6.4.2 - switch statements)

if one of the case constants is equal to the value of the condition, control is passed to the statement following the matched case label ... [the] labels in themselves do not alter the flow of control which continues unimpeded across such labels. To exit ... see break

I believe if you chose 3. It would say the 3 through 5.

if you did 2 it would say the 2 through 5.

if you just inputed 5 it would just say five.


That's what I think is going to happen here. Haven't actually tested it out but that's my guess.

Good job though!

Hai again!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

Here is the code:

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#include "stdafx.h"
#include <iostream>
using namespace std;


int main()
{
   int a;
   cout << "Please input a number 1-5" << endl;
   cin >> a;

   switch(a)
   {
   case 1: cout << "You chose 1" << endl;
   case 2: cout << "You chose 2" << endl;
   case 3: cout << "You chose 3" << endl;
   case 4: cout << "You chose 4" << endl;
   case 5: cout << "You chose 5" << endl;
   }
   return 0;
}


In case you didn't notice the error is on lines 14-18.

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case 1: cout << "You chose 1" << endl;
case 2: cout << "You chose 2" << endl;
case 3: cout << "You chose 3" << endl;
case 4: cout << "You chose 4" << endl;
case 5: cout << "You chose 5" << endl;


Oh noes! What do we do Argio?????????????????????????????

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case 1: cout << "You chose 1" << endl;
break;
case 2: cout << "You chose 2" << endl;
break;
case 3: cout << "You chose 3" << endl;
break;
case 4: cout << "You chose 4" << endl;
break;
case 5: cout << "You chose 5" << endl;
break;


Come on Argio, how does that work???

I don't even need to make strange references to real life objects... Yay!

Well, thing of it this way...

Before I fixed the program, it did not know to stop running through the checks when it found the right one. This resulted in the following things:

If I chose 2 I would get 2-5
If I chose 5 i would get 5 :p

So a simple break statement is needed. When you place a break statements it tells the computer to skip the rest of the if or switch statements when it finds the correct one.

YAY!