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Old 11-06-2003, 07:59 PM   #1
Registered: Jul 2003
Location: Istanbul
Distribution: slack
Posts: 43

Rep: Reputation: 15
Angry Exiting program with CTRL-Z C++

Here is the simple code for a calculator, however i want to exit when pressing CTRL-z on dos shell..In while loop something wrong i think
can you help me???

#include <stdlib.h>
#include <iostream>
#include <math.h>
#include <iterator>
using std::cout;
using namespace std;
int main()
float numberone;
float numbertwo;
float result;
char command_character;

do {

cout<<"Enter operation:";
cin >>numberone>>command_character>>numbertwo;
if ((numberone == 0) && (command_character== '^')) {
cout<<"error: Let's go to sleep"<<endl;
if ((command_character == '/' ) && (numbertwo == 0))
cout<<" Division by zero error"<<endl;
if ((numberone < 0) && (command_character =='^'))
if ((((command_character != '-' ) && (command_character != '+') && (command_character !='/' ) && (command_character != '^'))))
cout<<"error:undifined operator"<<endl;
else {
switch (command_character) {
case '+':
result = numberone + numbertwo;
case '/':
result = numberone / numbertwo;
case '-':
result = numberone - numbertwo;
case '*':
result = numberone * numbertwo;
case '^':
result = pow(numberone,numbertwo);
cout<<"The result is:"<<result<<endl;


} while ( != EOF); //// Here i try everyting but cannot managee.......!!!!

return 0;

Old 11-06-2003, 08:24 PM   #2
Senior Member
Registered: Nov 2002
Location: Silly Con Valley
Distribution: Red Hat 7.3, Red Hat 9.0
Posts: 2,054

Rep: Reputation: 46
well in dos, i think you need to add the <conio.h> header file and use getch() to get the characters individually. basically when you get the control key then do a test in that test branch and check if the next character is "z". if it is issue exit (0);

i'm not in windows at all and i can't look at the msdn documentation on using conio.h, but take a look at it.
Old 11-07-2003, 09:40 AM   #3
jim mcnamara
Registered: May 2002
Posts: 964

Rep: Reputation: 36
ctrl-z is ASCII 26. getc() would return 26, for example.

If this is windows programming one way is to call GetAsynchKeyState() to find when ctrl-z has been pressed. cin will not work in this case, AFAIK.
Old 11-08-2003, 11:41 PM   #4
Registered: Jun 2002
Location: Orange County, CA
Distribution: Debian (squeeze), kernel 2.6.30-2-amd64
Posts: 32

Rep: Reputation: 15
In a DOS session the Ctrl-Z key combination generates the end-of-file signal. In other words, "end-of-input", there's nothing more to be read. Although you see ^Z on the screen when you type Ctrl-Z, it doesn't actually generate those two characters. In C++ the way to see if end-of-file has been detected is to test for it; since you're using standard stream objects, that means using the "eof" member function.

Immediately after your extraction from stdin, try testing for EOF:

do {
cout<<"Enter operation:";
cin >>numberone>>command_character>>numbertwo;
if (cin.eof())  {
// we just read EOF, break out of the loop
BTW, I've noticed different behaviors with different WIndows platforms (e.g., Win95 vs. Win98 vs. Win2000 vs. XP, etc.). On some you can enter the Ctrl-Z after some input on the same line and don't have to press Enter, on others you can enter Ctrl-Z after some input on the same line but have to press Enter, but on all of them if you enter Ctrl-Z as the first character on a new line of input and press Enter it should be detected. (Why on earth MS keeps dinking around with the behavior of their consoles is beyond me...)

Have fun,


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