Simple question about pausing program

Noid · 04-01-2005, 01:31 AM

First off, I just started learning how to use C a few days ago by using a 1988 version of C Primer Plus. I think it's a little outdated, and I'm about to burn this book. But here is my question; I'm trying to get the simple programs in the tutorials to stay open so I can see what is happening ( they close immediately). I found this script (don't even know if it is called a script) on this website:

Code:

#include <stdio.h> 

int main(void)  /*wait for keypress*/
{
  int ch;
  printf ("Press [Enter] to continue");
  while ((ch = getchar()) != '\n' && ch != EOF);
  return(0);
}

it works when this is all that my program consists of, but when I try to add it to a program in one of the tutorials, such as:

Code:

#include <stdio.h> 

int main(void)  /*wait for keypress*/
{
 
float weight, value;
char beep;

beep = '\007';
printf("are you worth your weight in gold?\n");
printf("Please enter your weight in pounds, and we'll see.\n");  
scanf("%f", &weight);
value = 400.0*weight*14.5833;
printf("%cYour weight in gold is worth $%2.2f%c.\n", beep,value,beep);
printf("Your are easily worth that! If gold prices drop, ");
printf("eat more\nto maintain your value.\n");    
    
int ch;
printf ("Press [Enter] to continue");
 while ((ch = getchar()) != '\n' && ch != EOF);
 return(0);
  
 }

it does not ask for me to hit enter, but just closes after running the commands.

Did I enter something wrong?

If anyone helps with this simple problem, I am extremely greatful. I pretty much wasted a night on figuring this out, and I've given up searching for an answer on the web.

By the way, I'm using Dev-C++

Help me overcome! thanks

PING · 04-01-2005, 01:53 AM

http://faq.cprogramming.com/cgi-bin/...&id=1043284385

the faq at cprogramming.com is really nice..

**Dave_Sinkula** · 04-01-2005, 08:53 AM

Code:

scanf("%f", &weight);

You type a number followed by the enter key, right? The number is converted and the newline is left in the stdin. Without waiting for you to enter anything new, the newline is then consumed here.

Code:

while ((ch = getchar()) != '\n' && ch != EOF);

See also
FAQ > How do I... (Level 2) > Flush the input buffer

0rion · 04-01-2005, 11:31 AM

A simple method is to just add a "ch= getchar()" line that removes off the extra '\n' from the scanf() input.

Code:

#include <stdio.h> 

int main(void)  /*wait for keypress*/
{
 
	float weight, value;
	char beep;
	int ch;

	beep = '\007';
	printf("are you worth your weight in gold?\n");
	printf("Please enter your weight in pounds, and we'll see.\n");  
	scanf("%f", &weight);
	value = 400.0*weight*14.5833;
	printf("%cYour weight in gold is worth $%2.2f%c.\n", beep,value,beep);
	printf("Your are easily worth that! If gold prices drop, ");
	printf("eat more\nto maintain your value.\n");    

	ch=getchar();    
	printf ("Press [Enter] to continue");
	while ((ch = getchar()) != '\n' && ch != EOF);
	return (0);
}

quzah · 04-01-2005, 01:07 PM

Your "simple method" breaks if they type anything else other than one character past what you want them to. That's why we tell you to read the FAQ. Or rather, that's why it's been suggested two times already. Well, here's hoping "three times is a charm".

Quzah.

Quantum1024 · 04-01-2005, 01:38 PM

...or just run your program from the command prompt.

Noid · 04-01-2005, 05:42 PM

i have a long way to go...but these all get me past my problem, so I can continue with the tutorials.

Thanks everyone, I appreciate the help

0rion · 04-01-2005, 11:48 PM

Truth was I didn't really get how the FAQ code would flush the buffer in his case

Code from the FAQ:

Code:

#include <stdio.h> 

int main(void)
{
  int   ch;
  char  buf[BUFSIZ];
  
  puts("Flushing input");
  
  while ((ch = getchar()) != '\n' && ch != EOF);
  
  printf ("Enter some text: ");
  
  if (fgets(buf, sizeof(buf), stdin))
  {
    printf ("You entered: %s", buf);
  }
  
  return 0;
}

In this case there was nothing in the buffer before the while() loop which meant all it did was discard characters until a new line (or EOF) was reached. Since you stored it in ch, obviously the fgets() won't be effected. Or I'm not seeing something obvious here

Heh never mind I get it now! *smacks head*

coolshyam · 04-02-2005, 08:46 AM

dude.its all done.hope it works on Dev C++

Code:

#include <stdio.h> 
#include<dos.h>
int main(void)  /*wait for keypress*/
{
 
float weight, value;
char beep;

beep = '\007';
printf("are you worth your weight in gold?\n");
printf("Please enter your weight in pounds, and we'll see.\n");  
scanf("%f", &weight);
value = 400.0*weight*14.5833;
printf("%cYour weight in gold is worth $%2.2f%c.\n", beep,value,beep);
printf("Your are easily worth that! If gold prices drop, ");
printf("eat more\nto maintain your value.\n");    
    
int ch;
shyam:
printf ("Press [Enter] to continue");
ch=getchar();
 if ((ch = getchar()) != '\n' && ch != EOF)
 {
	 goto shyam;

 }
 else
 {
	goto ram;
 }
ram:
 return(0);
  
 }

please maintain structuring in your code.it will make our job of debugging easier.

Joelito · 04-02-2005, 09:02 AM

What's wrong with System("pause")?
I know some commands aren't portables but... either way can pause the programm... or I miss something?

quzah · 04-02-2005, 09:05 AM

Well, if you had read the FAQ...

But then, you already answered your own question. Why use a nonportable method when there are portable versions that work just as well?

But then, if you had read the FAQ...

Quzah.

Joelito · 04-02-2005, 09:10 AM

mmm, I did.. but if the program is ment to run only in my machine... and I can support those non-portable... wouldn't be heavy to use them, right?

quzah · 04-02-2005, 09:11 AM

Do whatever the ........ you want. No one here gives a ......... But when we try to help people, we're not just talking about "my machine". Therefore, we don't post stupid system specific answers when there's a portable option that's just as easy.

Quzah.

Joelito · 04-02-2005, 09:38 AM

So... quzah are you in flame war to me? Talk about free speaking.

quzah · 04-02-2005, 09:46 AM

You asked what was wrong with system( "pause" ), I told you. You replied that for you you'd use it anyway, I said I didn't care. End of discussion. If you want to carry it further, don't waste space in this thread, PM me.

Quzah.

04-01-2005, 01:31 AM	#1
Noid Registered User Join Date: Apr 2005 Posts: 2	Simple question about pausing program First off, I just started learning how to use C a few days ago by using a 1988 version of C Primer Plus. I think it's a little outdated, and I'm about to burn this book. But here is my question; I'm trying to get the simple programs in the tutorials to stay open so I can see what is happening ( they close immediately). I found this script (don't even know if it is called a script) on this website: Code: #include <stdio.h> int main(void) /wait for keypress/ { int ch; printf ("Press [Enter] to continue"); while ((ch = getchar()) != '\n' && ch != EOF); return(0); } it works when this is all that my program consists of, but when I try to add it to a program in one of the tutorials, such as: Code: #include <stdio.h> int main(void) /wait for keypress/ { float weight, value; char beep; beep = '\007'; printf("are you worth your weight in gold?\n"); printf("Please enter your weight in pounds, and we'll see.\n"); scanf("%f", &weight); value = 400.0weight14.5833; printf("%cYour weight in gold is worth $%2.2f%c.\n", beep,value,beep); printf("Your are easily worth that! If gold prices drop, "); printf("eat more\nto maintain your value.\n"); int ch; printf ("Press [Enter] to continue"); while ((ch = getchar()) != '\n' && ch != EOF); return(0); } it does not ask for me to hit enter, but just closes after running the commands. Did I enter something wrong? If anyone helps with this simple problem, I am extremely greatful. I pretty much wasted a night on figuring this out, and I've given up searching for an answer on the web. By the way, I'm using Dev-C++ Help me overcome! thanks
Noid is offline

04-01-2005, 01:53 AM	#2
PING Registered User Join Date: Nov 2004 Location: india Posts: 493	http://faq.cprogramming.com/cgi-bin/...&id=1043284385 the faq at cprogramming.com is really nice.. __________________ Go Petr !! My Blog
PING is offline

04-01-2005, 08:53 AM	#3
Dave_Sinkula Just Lurking Join Date: Oct 2002 Posts: 4,990	Code: scanf("%f", &weight); You type a number followed by the enter key, right? The number is converted and the newline is left in the stdin. Without waiting for you to enter anything new, the newline is then consumed here. Code: while ((ch = getchar()) != '\n' && ch != EOF); See also FAQ > How do I... (Level 2) > Flush the input buffer __________________ 7. It is easier to write an incorrect program than understand a correct one. 40. There are two ways to write error-free programs; only the third one works.*
Dave_Sinkula is offline

04-01-2005, 01:07 PM	#5
quzah +++ OK NO CARRIER Join Date: Oct 2001 Posts: 10,259	Your "simple method" breaks if they type anything else other than one character past what you want them to. That's why we tell you to read the FAQ. Or rather, that's why it's been suggested two times already. Well, here's hoping "three times is a charm". Quzah. __________________ Hundreds of thousands of dipshits can't be wrong. Are you up for the suck?
quzah is offline

04-01-2005, 01:38 PM	#6
Quantum1024 Registered User Join Date: Jan 2005 Posts: 847	...or just run your program from the command prompt.
Quantum1024 is offline

04-01-2005, 05:42 PM	#7
Noid Registered User Join Date: Apr 2005 Posts: 2	i have a long way to go...but these all get me past my problem, so I can continue with the tutorials. Thanks everyone, I appreciate the help
Noid is offline

04-01-2005, 11:48 PM	#8
0rion Registered User Join Date: Apr 2004 Posts: 171	Truth was I didn't really get how the FAQ code would flush the buffer in his case Code from the FAQ: Code: #include <stdio.h> int main(void) { int ch; char buf[BUFSIZ]; puts("Flushing input"); while ((ch = getchar()) != '\n' && ch != EOF); printf ("Enter some text: "); if (fgets(buf, sizeof(buf), stdin)) { printf ("You entered: %s", buf); } return 0; } In this case there was nothing in the buffer before the while() loop which meant all it did was discard characters until a new line (or EOF) was reached. Since you stored it in ch, obviously the fgets() won't be effected. Or I'm not seeing something obvious here Heh never mind I get it now! smacks head Last edited by 0rion; 04-01-2005 at 11:50 PM.
0rion is offline

04-02-2005, 09:02 AM	#10
Joelito Registered User Join Date: Mar 2005 Location: Tijuana, BC, México Posts: 282	What's wrong with System("pause")? I know some commands aren't portables but... either way can pause the programm... or I miss something?
Joelito is offline

04-02-2005, 09:05 AM	#11
quzah +++ OK NO CARRIER Join Date: Oct 2001 Posts: 10,259	Well, if you had read the FAQ... But then, you already answered your own question. Why use a nonportable method when there are portable versions that work just as well? But then, if you had read the FAQ... Quzah. __________________ Hundreds of thousands of dipshits can't be wrong. Are you up for the suck?
quzah is offline

04-02-2005, 09:10 AM	#12
Joelito Registered User Join Date: Mar 2005 Location: Tijuana, BC, México Posts: 282	mmm, I did.. but if the program is ment to run only in my machine... and I can support those non-portable... wouldn't be heavy to use them, right?
Joelito is offline

04-02-2005, 09:11 AM	#13
quzah +++ OK NO CARRIER Join Date: Oct 2001 Posts: 10,259	Do whatever the ........ you want. No one here gives a ......... But when we try to help people, we're not just talking about "my machine". Therefore, we don't post stupid system specific answers when there's a portable option that's just as easy. Quzah. __________________ Hundreds of thousands of dipshits can't be wrong. Are you up for the suck?
quzah is offline

04-02-2005, 09:38 AM	#14
Joelito Registered User Join Date: Mar 2005 Location: Tijuana, BC, México Posts: 282	So... quzah are you in flame war to me? Talk about free speaking.
Joelito is offline

04-02-2005, 09:46 AM	#15
quzah +++ OK NO CARRIER Join Date: Oct 2001 Posts: 10,259	You asked what was wrong with system( "pause" ), I told you. You replied that for you you'd use it anyway, I said I didn't care. End of discussion. If you want to carry it further, don't waste space in this thread, PM me. Quzah. __________________ Hundreds of thousands of dipshits can't be wrong. Are you up for the suck?
quzah is offline

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