cin not working even with proper header

Guys .. I've got a prob here..

cin isn't working.. see code below..


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

  void ins()
{
clrscr();
int d=1,e=2,f;
cout<<"Insert Tray                            Single - "<<d;
cout<<"\nLoad Drum                              Double - "<<e;
cin>>f;
if(f == d)
cout<<"Single";
else if(f == e)
cout<<"Double";
else
cout<<"Invalid Entry";
getch();
}


void main()
{
ins();
}

Well ... The program isn't taking input from me.. The screen appears that

Insert Tray Single - 1
Load Drum Double - 2Invalid Entry

The program shows invalid entry without taking input from me...Help pls
//Using Turbo C++

Last edited on Sep 15, 2015 at 3:43pm

Sep 15, 2015 at 3:40pm

To read from cin you should use >>

Sep 15, 2015 at 3:43pm

@Peter87

Yet not working

Sep 15, 2015 at 3:51pm

Are you sure this is the code? If you are using cin before calling ins() the problem could be there.

Sep 15, 2015 at 3:53pm

Yes this is the code ..Fully sure..
Well .. Lemme show full code..

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

void wlcscrn()
{
clrscr();
cout<<"                      Universal Lab           ";
cout<<"\n    ULF VER : 01/01                   15/09/2015";
delay(3000);
}

void login()
{
clrscr();
char a, b, c;
cout<<"Username - ";
cin>>a;
cout<<"Password - ";
b = getch();
while(b != 13){
cout<<'*';
b = getch();
}
clrscr();
cout<<"Login Successful";
delay(2000);
}

void ins()
{
clrscr();
int d=1,e=2,f;
cout<<"Insert Tray                            Single - "<<d;
cout<<"\nLoad Drum                              Double - "<<e;
cin>>f;
if(f == d)
cout<<"Single";
else if(f == e)
cout<<"Double";
else
cout<<"Invalid Entry";
getch();
}

void main()
{
wlcscrn();
login();
ins();
}

Last edited on Sep 15, 2015 at 3:55pm

Sep 15, 2015 at 4:05pm

Disch (13742)

Using Turbo C++

Maybe try a compiler that isn't 25 years old?

Sep 15, 2015 at 4:21pm

I can't run it because I don't have Turbo C++ but one thing I spotted is that you only allow the username to be one character (a is a char). If you input more than one character the rest of them will be read as the password.

Sep 15, 2015 at 4:58pm

dhayden (5798)

You're mixing stream input and stdio input in function login(). This causes unexpected behavior. To see what's going on I changed ins:

void ins()
{
    clrscr();
    int d=1,e=2,f = -1;
    cout<<"Insert Tray                            Single - "<<d;
    cout<<"\nLoad Drum                              Double - "<<e << '\n';

    string str;
    getline(cin, str);
    cout << "cin has \"" << str << "\"\n";
    if (!(cin>>f)) {
	cout << "Can't read number\n";
    } else if (f == d)
	cout<<"Single";
    else if(f == e)
	cout<<"Double";
    else
	cout<<"Invalid Entry " << f << '\n';;
    getch();
}

When I enter UserName Dave and password hello, it responds with

cin has "ave"

Looking at line 19, you input only a single character for the username instead of a string. So the rest of the string is in the input buffer and that's what you get when trying to read the username.

Sep 17, 2015 at 5:57am

Well .. guys .. @Disch - Turbo C++ must be 25 years old but the college uses the software and hence i'm bind to use it .. else i'd had obviously used codeblocks..

@Peter87 and @dhayden ... I have no problem whatever happens in the login function... I just had prob in the ins function in which the cin isn't reading... Thats why i don't usually post my whole code in here.. Okay .. If anybody knows what should I do Please Reply

@dhayden I don't know why .. I've Put the header file as #include<string.h> still when i type string in the code .. it says thats invalid... and when i put #include<string> then one more error rises saying that no header file like that..

Even need help in that situation... Sorry if I annoyed someone... I'm just a beginner , newbie, and maybe noob.. Please reply..

Sep 17, 2015 at 7:01am

closed account (48T7M4Gy)

How old are the PC's?

Sep 17, 2015 at 12:48pm

jlb (4973)

Are your names and passwords a single character? Entering more that a single character for these variables will cause problems because you defined the variables as single characters. If you enter multiple characters for these variables you'll probably have problems later in your program because you'll probably have characters left in the input buffer when you leave the login function. By the way why does the login function always succeed no matter what you try to enter for the password.

Since you're using such an outdated compiler you probably shouldn't try to use a C++ string since that compiler's version of the string class is quite different than the standard C++ string class. You'll be better off using C-strings instead.

Sep 17, 2015 at 1:29pm

MannedTooth (11)

Where is your

using namespace std;

Sep 17, 2015 at 1:49pm

MannedTooth wrote:
Where is your `using namespace std;` ?

Turbo C++ doesn't have namespaces.

Sep 17, 2015 at 2:14pm

MannedTooth (11)

Oh, my mistake. :P

Sep 17, 2015 at 2:28pm

dhayden (5798)

I have no problem whatever happens in the login function

Just because it appears to work doesn't mean it is problem free. At line 19 you do this:
cin>>a;
Which reads a single character, leaving whatever else you typed for the username in the input buffer. So when you do cin>>f in inp(), it fails because you're asking it to interpret the 2nd-nth characters of the username as a number.

Sep 20, 2015 at 5:31am

Ahh guys... I said i don't care whatever the login function does.. I just have problem in ins fuction ... Thats where the cin is not reading.. I don't mean to be rude but you guys are stuck at login function yet and i need solution to ins function... Login function doesn't matter to me at all and that is just for a output .. Means just for show.. Showpiece some like that... Please reply for ins function...

Sep 20, 2015 at 6:13am

closed account (48T7M4Gy)

#include<iostream>
#include<string>

void ins()
{
    int d=1, e=2, f;
    std::cout << "Insert Tray                            Single - " << d;
    std::cout << "\nLoad Drum                              Double - " << e;
    std::cin >> f;

    if(f == d)
        std::cout<<"Single";
    else if(f == e)
            std::cout<<"Double";
        else
            std::cout<<"Invalid Entry";
}

int main()
{
    ins();
    
    return 0;
}

Sep 20, 2015 at 1:30pm

dhayden (5798)

i don't care whatever the login function does

Even if it doesn't work?

I just have problem in ins fuction

No, you have a symptom in the ins function. You have a problem in the login function.

If your problem is in the ins() function, then why is it that when I fix login(), your ins() function works properly?

I have already explained the problem. I've explained why the symptom shows up in ins(). Your refusal to take the help really baffles me.

Often the symptom of a programming bug doesn't show up until later on in the code. Here's a trivial example:

#include<iostream>
int add(int a, int b)
{
    return a - b;		// bug is here
}

void main()
{
    std::cout << add(3,1) << '\n'; // bug shows up here.
}

Sep 23, 2015 at 4:18pm