Thread: getch() and other oddities

Hye everyone,
So check this out...I have this code, I know it doesnt do anything...it's for test purposes:

Code:

cout << "What is your name?";
char ch = getch();
while (ch != '\r')
{
   if (ch >= '0' && ch <= '9')
   {  
       cout << ch;
   }
   
   ch = getch();
}

So what this does is basically only allows the user to enter numbers...but a few questions arise...due to the restrictions of this, the ability to delete is cut off...I tried testing for ch == '\b' but that only went back a space everytime I hit delete...not exactly helpful...any creative solutions around this?...I searched online for a while and didnt find any escape sequence that would mean a delete...I was actually surprised by that.


Ok so there's that...and then there's this...so using my backspacing I was able to start overwriting the string literal "What is your name?"...so now my question is does that affect your program at all? I mean I'm not exactly sure what is happening with backspacing on top of already printed to the screen characters...so...any insight into whether only aesthetic issues arise or if I'm tapping into anything bad...I dunno...just curious...sorry if I'm not making myself clear, any help would be the *expletive deleted for the sake of all readers* -Chap

About backspacing, if you can figure out what character to test for to move back one space (does '\b' work?), you can just write code that backspaces 1 place, writes a ' ' character, and backspaces again, whenever you come across that character.

Hunter you're right...jesus...I'm such an idiot! Why the hell didnt I think of that...I think I jumped too quickly into the mentality of "I need to get an answer to this or my head will explode!!"...arg...

Overwriting "What is your name?" is not overwriting the string literal

I must apologize...my choice of wording was foolish, I meant overwriting in an aesthetic sense...although you did bring up a cool point about how all we're looking at is a literal that's meant to be modified, I never really looked at it like that, thanks for the shift of perspective...but now...when I backspace over this literal thats been printed to the screen...is there actual memory that's being overwritten? Even if its the memory of the copy...memory is still being overwritten? I thought it was just printing the character because I told it to and there was no real internal anything going on...

One last thing...if getch() returns a single character...is it possible to prevent \b from going past the starting point of input...I mean, can I test for an element index of any kind?
Questions questions everywhere!!

what do you mean by <<flush? curiously...

on an unrelated note...I like how you can start off with simple enough code and then as you enter more capabilities and start factoring in how a user is going to handle your program, you start to develop these more complex chunks of code...what started off with a simple while statement testing one if inside has now turned into nested ifs within a while...I dunno...just thought it was cool, the beauty of being a beginner

Code:

std::cout << "Hello! Part of this message might not be output to the screen!";

Interesting, what factors could potentially stop this from being output?

I havent come across flush up until now so I'm trying to get as much info now, should flush solely be used for debugging purposes? Sorry I'm full of questions haha...I'm a curious mofo...

ok...any particular examples of what would cause the output buffer to withhold some of its contents? this is all very interesting...

Originally Posted by Chaplin27

ok...any particular examples of what would cause the output buffer to withhold some of its contents? this is all very interesting...

Typically the output buffer doesn't flush unless a newline character is sent, the program is waiting for input, or it's forced to flush.

Here's an example where the output doesn't flush when you'd expect it to. Timer 1 doesn't flush until it's complete, and Timer 2 flushes at each tick.

Code:

#include <iostream>
#include <ctime>
using namespace std;

#define TIMER 10

void timer1();
void timer2();

int main ()
{
	timer1();
	timer2();
	
	return 0;
}

void timer1()
{
	int tick = 0;
	clock_t delay = CLOCKS_PER_SEC * TIMER;
	clock_t start = clock();
	
	cout << "Timer one:" << endl;
	
	while ( clock() - start <= delay )
	{
		if ( ( clock() - start ) / CLOCKS_PER_SEC > tick)
			cout << ++tick;
	}
	cout << endl << endl;
}

void timer2()
{
	int tick = 0;
	int delay = TIMER;
	int start = time(0);
	
	cout << "Timer two:" << endl;
	
	while ( start + TIMER > time(0) )
	{
		if ( time(0) - tick > start )
			cout << ++tick << endl;
	}
}