this is my code
#include <conio.h>
#include <iostream>
using namespace std;
int main() {
bool a = false;
char b='p';
int c=0;
while (a != true) {
if (_kbhit()) {
b = _getch();
}
if (b=='w') {
c++;
cout << c << " ";
}
else if (b == 'c') {
cout << "hello";
}
}
system("pause");
return 0;
}
The problem is where when I press 'w' I want it to print out the value of c and it should be repeating until i press another input for _kbhit() right? because now it add 1 to c then prints c and when i press w again samething. What's wrong with my visual studio I'm using community 2017 I've tried to uninstall it and install it again but same problem occurs.
The problem you're running into seems to be a result of a recently added bug in _getch()/_kbhit.
For an extended key (e.g., a cursor key) it's documented that _getch() returns either a 0x0 or 0xe0 followed by the scan code for the key that was actually pressed. What's not documented is that if the user presses a non-extended key, _kbhit will still return true twice in succession, and calls to _getch() will return the key code the first time, and 0x0 the second time.
In your code, when the user presses 'w' or 'c', _kbhit will return true not just once (as you'd expect) but twice. The first time you call it, it'll return the scan code of the key, and the second it'll return a 0 byte.
What's happening in your code is that you're reading the scan code, printing something appropriately, then _kbhit is returning true again, so you read the '\0' byte, set b to '\0', and then (since you don't have any code to do anything when b is 0) you (repeatedly) do nothing until the next time the user presses a key.
Reference
https://learn.microsoft.com/en-us/cpp/c-runtime-library/reference/getch-getwch?view=vs-2017
It seems like the program behaves the way you want it to. If I press 'w', it goes into an infinite loop of increasing the value of c and printing it. Pressing any other key stops printing and pressing 'c' goes on the same infinite loop and prints hello. Doesn't seem to be any problems as far as the posted code is concerned. Also, I would like to say the same as #Someprogrammerdude, if it compiles, but doesn't behave the way you want it to, it's an issue with the code, not the IDE and/or compiler.
Hypothetical answer: Your computer might always be thinking that a key is pressed, thus kbhit() always returns true. This maybe caused by a bad mouse/keyboard/controller driver and/or configuration. The code is fine, your PC is not.
Related
I would like to use arrow keys user input without the user having to press enter every time after clicking the arrow. Therefore, I decided to use _getch(), which allegedly does exactly that. It is part of the conio.h library, which I imported. However, in my case,_getch() also requires the user to press enter and doesn't immediately register the user input, as it should've. How can I fix that? (I'm running on windows)
#include<iostream>
#include <conio.h>
using namespace std;
int main() {
int p = _getch();
cout<<p;
return 0;
}
For example, in the code above instead of directly printing the value of p after receiving input in the console, it still waits for enter to be pressed.
From Microsoft Docs:
When reading a function key or an arrow key, each function must be called twice; the first call returns 0 or 0xE0, and the second call returns the actual key code.
So a revised version of your code might look like this:
#include <iostream>
#include <conio.h>
int main() {
int p = 0;
while(p == 0 || p == 0xE0)
p = _getch();
std::cout << p;
return 0;
}
I am working on a class project where I have to create an ordering system for a coffee shop in C++. If it is applicable, I'm working in Visual Studio.
In the project outline, the teacher said that there is a simple integer input to navigate the menu; however, he specifies that if NOTHING is inputted (I'm assuming what I've seen called a "hot enter") that it calculates the receipt and the program resets.
I have tried cin.get() and checking if the buffer is '\n', and this works fine, but my current implementation seems to only be able to capture a hot enter, and fails to roll into the switch case.
For getting input from the user, I've currently tried this:
// Get menu input
if (cin.get() == '\n') { // Check if user hot entered, assign value if so
input = 0;
} else { // If not, do it normally
input = cin.get();
}
However this does not work quite right, and fails to capture inputted integers for use in the switch case. I'm unsure if this sort of implementation is sound in reasoning, or whether there is a much simpler route to have a case for a hot enter.
I don't receive any errors, so I imagine there is something wrong with my understanding of how these functions work, or my implementation is flawed in its logic.
Thank you.
You used cin.get() twice. The second cin.get() in input = cin.get(); is redundant.
// Get menu input
input = cin.get();
if (input == '\n') { // Check if user hot entered, assign value if so
input = 0;
}
//else { // If not, do it normally
// input = cin.get();
// }
Today i was testing how key pressing might work in C++ and made simple loop for it,and found that getch() duplicate itself for some reason or idk what is going on honestly,just look at that:
#include <iostream>
#include <windows.h>
#include <conio.h>
#define VK_H 0x48
using namespace std;
int main()
{
int n=1;
int total=0;
bool theEnd=true;
while(theEnd)
{
cout<<total<<endl;
getch();
if(GetAsyncKeyState(VK_LEFT))
{
total -=n;
}else if(GetAsyncKeyState(VK_RIGHT))
{
total +=n;
}else if(GetAsyncKeyState(VK_LSHIFT) && GetAsyncKeyState(VK_F1))
{
total = 0;
} else if(GetAsyncKeyState(VK_ESCAPE))
{
break;
}
}
cout<<total<<endl;
}
Its pretty simple.Program starts with a loop,where endlessly outputs value of variable "total",and after pressing left/right buttons "total" decrements/increments by 1.
Its was worked fine and perfect when i was using system("pause"); Sleep(milliseconds); cin.get();(but this one assume pressing enter each time,so it is not proper one) ,all that output right value on the screen after each pressing on the buttons.But in case with getch(); it somehow appear to working like only one time per/two cycles of the loop.
So the result i've get is like this: i'm pressing button right - current loop working fine,but next one working like without getch(),incrementing and outputting one more time without my command...
I've siting and thinking couple hours,trying find any answers in google and here but nothing...
P.S.without using getch() or other things for purpose stoping loop till next pressing - it will add not +1 to total by single pressing(as i need),but hundreds(average pressing key will do 150-300 loops lol).
From MS documentation
Remarks
The _getch and_getwch functions read a single character from the
console without echoing the character. None of these functions can be
used to read CTRL+C. When reading a function key or an arrow key, each
function must be called twice; the first call returns 0 or 0xE0, and
the second call returns the actual key code.
When you press arrow keys, the input is 2 chars
I have created an application for detect pressing up and down key on keyboard
but nothing will be printed after pressing these keys.
I am using Visual C++ 2010
#include <iostream>
#include <conio.h>
using namespace std;
void main()
{
char x;
while(1)
{
x = getch();
if(x==0 || x==224)
{
x=getch();
if(x==80)
{
cout << "down"<<endl;
}
else if(x==72)
{
cout << "up"<<endl;
}
}//if x==0 || x=224
}//while1
}//main
What can be the problem?
Thanks
Just to answer why it isn't working: You are trying to use your user's input as unsigned. Your character variable is signed so the value is different than you are expecting. An unsigned 224 is a signed -32.
As far as your loop goes I'd suggest changing things to this.
void main()
{
char x;
while(true)
{
while(!kbhit()){}
x = getch();
if(x==0 || x==-32)
{
x=getch();
if(x==80)
{
cout << "down"<<endl;
}
else if(x==72)
{
cout << "up"<<endl;
}
}//if x==0 || x=224
}//while1
}//main
The program will still loop forever. Then the next loop, which I added, will continue to loop while there are no keys being pressed(buffered). Then getch() grabs the next char from the buffer. Now the problem you were running into, is that you had 224 (0xE0) which is technically correct. However in binary apparently -32 and 224 look the same.
I ran into a bit of the same issue at first, I couldn't figure out why my code wasn't hitting the correct code block and it was because the first character was actually -32 (0xE0)
Hope that is of some help, despite this being a really old question.
You can use the curses.h library. Read their guide and it should be very easy from there.
After you take input using getch() (store the input into an int, not a char), you can verify if it's one of the arrow keys using the defined keycodes. Just make sure you used keypad(stdscr, TRUE) before for the program to be able to recognize the arrow keys.
Us kbhit() to get Keyboard Arrow Keys
I'm trying to write a Windows console application (in C++ compiled using g++) that will execute a series of instructions in a loop until finished OR until ctrl-z (or some other keystroke) is pressed. The code I'm currently using to catch it isn't working (otherwise I wouldn't be asking, right?):
if(kbhit() && getc(stdin) == 26)
//The code to execute when ctrl-z is pressed
If I press a key, it is echoed and the application waits until I press Enter to continue on at all. With the value 26, it doesn't execute the intended code. If I use something like 65 for the value to catch, it will reroute execution if I press A then Enter afterward.
Is there a way to passively check for input, throwing it out if it's not what I'm looking for or properly reacting when it is what I'm looking for? ..and without having to press Enter afterward?
Try ReadConsoleInput to avoid cooked mode, and GetNumberOfConsoleInputEvents to avoid blocking.
If G++ supports conio.h then you could do something like this:
#include <conio.h>
#include <stdio.h>
void main()
{
for (;;)
{
if (kbhit())
{
char c = getch();
if (c == 0) {
c = getch(); // get extended code
} else {
if (c == 'a') // handle normal codes
break;
}
}
}
}
This link may explain things a little more for you.