I am self study C student. I got stuck in the program below on quadratic equation and will be most grateful if someone could help me to unravel the mystery.
Why does the computer refuse to execute my scanf ("%c",&q);
On input 3 4 1 (for a,b and c) I had real roots OK
On input 1 8 16 I had same real roots OK.
However on 4 2 5, (for imaginary roots ) the computer cannot see the scanf ("%c",&q); statement. It just jumps over it.
How can I make the computer not to ignore this statement? I am on Visual C++ platform.
Thanks
Khoon.
/* Roots of a Quadratic Equation.
12.10.05 */
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
int main (void)
{
int a; int b; int c; float x1; float x2; int E; int E1; float R; float I;float S;
char p; char q; char y;
printf ("Please key in the value of constant a,b and c for finding the roots of quadratic");
printf ("equation ax%c+bx+c=0 :",253);
scanf ("%d%d%d", &a,&b,&c);
E =(b*b)-(4*a*c);
if ( E > 0)
{
x1 = (float)(-b+sqrt(E))/(2*a);
x2 = (float)(-b-sqrt(E))/(2*a);
printf ("\nYour quadratic equation has two distinct real roots: x1=%1.6f ,x2=%1.6f",x1,x 2);
}
else if (E == 0)
{
x1 = (float)(-b+sqrt(E))/(2*a);
printf ("\nYour quadratic equation has two same: x1=x2=%1.6f\n", x1);
}
else
{
p = 'y';
printf ("Your quadratic equation has two distinct imaginary roots. Do you want to know\n");
printf ("the values of the imaginary roots (Y/N)?");
scanf ("%c",&q);
printf ("\nq = %c\n",q);/* Test statement*/
if (p==q)
printf ("OK I will show your the imaginary roots tomorrow.\n");
else
printf ("Good bye\n");
return 0;
}
}
Nov 15 '05
38  2548 
Red Dragon wrote: "Mark McIntyre" <ma**********@s pamcop.net> wrote in message
news:5t******** *************** *********@4ax.c om...On Tue, 18 Oct 2005 17:57:50 +0800, in comp.lang.c , "Red Dragon"
<ts*****@stre amyx.com> wrote:
I dont quite understand the phrase "newline to terminate the line".How many keys do you press, when you supply user input value of 1? One
key or two?
--
Mark McIntyre
2 keys. One for 1 and One for Enter.
Can you kindly tell me is using 2 scanf() the best solution to the problem?
No, What would happen if the user entered more than one character on the
line before entering Enter?
What is a better method?
Have a look at the getchar() function. Use that to write a bit of code
that will keep getting characters until it receives a new line.
Kevin Bagust.
On Wed, 19 Oct 2005 19:02:32 +0800, in comp.lang.c , "Red Dragon"
<ts*****@stream yx.com> wrote:
"Mark McIntyre" <ma**********@s pamcop.net> wrote in message
news:5t******* *************** **********@4ax. com... On Tue, 18 Oct 2005 17:57:50 +0800, in comp.lang.c , "Red Dragon"
<ts*****@stream yx.com> wrote:
I dont quite understand the phrase "newline to terminate the line".
How many keys do you press, when you supply user input value of 1? One
key or two?
--
Mark McIntyre
2 keys. One for 1 and One for Enter.
.... so you see now where the newline comes from.
Can you kindly tell me is using 2 scanf() the best solution to the problem?
What is a better method?
Personally I prefer to fgets() into a char array of known size, then
parse the array via eg sscanf. I can then decide if there's still
input waiting to be read, and if so I can empty it via repeated calls
to say getchar.
This is probably a FAQ (12.18, 12.20, 12.26 all seem relevant to this
discussion, plus a few others in that area).
--
Mark McIntyre
CLC FAQ <http://www.eskimo.com/~scs/C-faq/top.html>
CLC readme: <http://www.ungerhu.com/jxh/clc.welcome.txt >
----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups
----= East and West-Coast Server Farms - Total Privacy via Encryption =----
I tried getchar() and found it has same effect as scanf()
Anyway thanks at lot.
Rgds,
Khoon.
"Red Dragon" <ts*****@stream yx.com> writes: I tried getchar() and found it has same effect as scanf()
Anyway thanks at lot.
Rgds,
Khoon.
Surely you've been here long enough to know how to post a proper
followup using Google Groups. I've even seen you do it in this
thread.
Incidentally, saying that getchar() has the same effect as scanf() is
meaningless without context. They're obviously two different
functions, doing different things. If you'll show us some code, we
can suggest improvements.
--
Keith Thompson (The_Other_Keit h) ks***@mib.org <http://www.ghoti.net/~kst>
San Diego Supercomputer Center <*> <http://users.sdsc.edu/~kst>
We must do something. This is something. Therefore, we must do this.
"Keith Thompson" <ks***@mib.or g> wrote in message news:ln******** ****@nuthaus.mi b.org... "Red Dragon" <ts*****@stream yx.com> writes: I tried getchar() and found it has same effect as scanf()
Anyway thanks a lot.
Rgds,
Khoon.
Surely you've been here long enough to know how to post a proper
followup using Google Groups. I've even seen you do it in this
thread.
Sorry. What is Google Groups? I am using Outlook Express and Visual C++ platform.
Incidentally, saying that getchar() has the same effect as scanf() is
meaningless without context. They're obviously two different
functions, doing different things. If you'll show us some code, we
can suggest improvements.
Thank you. Here is a program to illustrate my point.
/*Program to Demonstrate getchar() and scanf()*/
#include <stdio.h>
int main (void)
{
char a,b;
/*Section 1*/
printf("Enter a character > ");
scanf("%c",&a);
printf("a=%c\n" ,a);
printf("Enter another character > ");
getchar("%c",&b );
printf("b=%c\n" ,b);
/*section 2*/
printf("\nEnter a character > ");
scanf("%c",&a);
printf("a=%c\n" ,a);
printf("Enter another character > ");
scanf("%c",&b);
printf("b=%c\n" ,b);
/*section 3*/
printf("\nEnter a character > ");
scanf("%c",&a);
printf("a=%c\n" ,a);
printf("Enter another character > ");
scanf("%c",&b); /* Dummy */
scanf("%c",&b);
printf("b=%c\n" ,b);
return 0;
}
/*PRINT RESULT
Enter a character > a
a=a
Enter another character > b=¦
Enter a character > a
a=a
Enter another character > b=
Enter a character > a
a=a
Enter another character > b
b=b
Press any key to continue
*/
You can see that I have divided the program into 3 sections.
1st section with getchar()
2nd section with single scanf()
3rd section with double scanf()
In the Printout Result, only 3rd Section with a Dummy performed perfectly.
BTW, Do you have HTML problem with my program above?
Regards and thank you very much.
Khoon.
"Red Dragon" <ts*****@stream yx.com> writes: "Keith Thompson" <ks***@mib.or g> wrote in message
news:ln******** ****@nuthaus.mi b.org... "Red Dragon" <ts*****@stream yx.com> writes: I tried getchar() and found it has same effect as scanf()
Anyway thanks a lot.
Surely you've been here long enough to know how to post a proper
followup using Google Groups. I've even seen you do it in this
thread.
Sorry. What is Google Groups? I am using Outlook Express and Visual C++
platform.
Sorry, my mistake.
groups.google.c om has a broken interface that encourages users to post
followups with no attributions or quoted text. I don't know why I
didn't check your article's headers before assuming you were using
Google Groups.
In general, posting a followup that doesn't quote any of the parent
article is considered rude.
Incidentally, saying that getchar() has the same effect as scanf() is
meaningless without context. They're obviously two different
functions, doing different things. If you'll show us some code, we
can suggest improvements.
Thank you. Here is a program to illustrate my point.
/*Program to Demonstrate getchar() and scanf()*/
#include <stdio.h>
int main (void)
{
char a,b;
/*Section 1*/
printf("Enter a character > ");
scanf("%c",&a);
printf("a=%c\n" ,a);
printf("Enter another character > ");
getchar("%c",&b );
printf("b=%c\n" ,b);
Ok, I was starting to write an explanation of what this code does when
I noticed this call:
getchar("%c",&b );
getchar() takes no arguments and returns an int value representing
the value of the input character or EOF. You have the required
"#include <stdio.h>" at the top of the program, so the compiler
knows this. Any working C compiler should give you an error message
on that line, or at least a warning.
Either you're running the compiler in a mode that causes it not to
display the error message (don't do that), or you're getting a warning
and ignoring it (don't do that), or the code you posted isn't the same
as the code you compiled (once again, don't do that).
If you're going to post code, you need to copy-and-paste the *exact*
code that you fed to the compiler. If you try to re-type it, you'll
make mistakes (I know I would), and there's no way we can guess which
errors are in the original code and which you introduced by re-typing
it.
If that really was the code you compiled, including the getchar() call
with too many arguments, you need to compile without turning off
diagnostic messages, and you need to fix any errors flagged by the
compiler.
[...]
BTW, Do you have HTML problem with my program above?
Not that I can see, but I think my newsreader sometimes quietly
renders HTML as plain text.
--
Keith Thompson (The_Other_Keit h) ks***@mib.org <http://www.ghoti.net/~kst>
San Diego Supercomputer Center <*> <http://users.sdsc.edu/~kst>
We must do something. This is something. Therefore, we must do this. In general, posting a followup that doesn't quote any of the parent
article is considered rude.
Yes. I agree with that. Incidentally, saying that getchar() has the same effect as scanf() is
meaningless without context.
I was responding to the suggestion by Kevin Bagust to try using getchar() to solve the problem of scanf() being unable to read input character. As I learnt from Mark McIntyre, it could not read my character input because it was reading "newline' and jumped. This problem was demonstrated in my exhibit program as Section 1 using getchar() and section 2 using single scanf(), both failed to execute. Only when I used double scanf() was the problem solved.
Ok, I was starting to write an explanation of what this code does when
I noticed this call:
getchar("%c",&b );
getchar() takes no arguments and returns an int value representing
the value of the input character or EOF. You have the required
"#include <stdio.h>" at the top of the program, so the compiler
knows this. Any working C compiler should give you an error message
on that line, or at least a warning.
I started C programing a month ago, self study on a book " A Structured Programming Approach Using C by Forouzan and Gilberg. I think it is very good.
Now I am on into Looping in Chapter 6, and I see getchar() is a topic in Chapter 7.
Either you're running the compiler in a mode that causes it not to
display the error message (don't do that), or you're getting a warning
and ignoring it (don't do that), or the code you posted isn't the same
as the code you compiled (once again, don't do that).
When I compiled my code as shown in my previous program, I got 0 errors and 0 warnings.
If you're going to post code, you need to copy-and-paste the *exact*
code that you fed to the compiler. If you try to re-type it, you'll
make mistakes (I know I would), and there's no way we can guess which
errors are in the original code and which you introduced by re-typing
it.
When Tim Rentsch posted back to me what he had received, I was horrified by the load of gibberish HTML codes I had inadvertently created.
What I had earlier done was to copy from my Visual C++ platform and paste into Outlook Express. What I now do is to cut and paste into Notepad, and then cut from Notepad and paste into Outlook. In this way, I reckon I have killed all the HTML code. I did not do any retyping.
BTW, Do you have HTML problem with my program above?
Not that I can see, but I think my newsreader sometimes quietly
renders HTML as plain text.
Thank you very much.
Regards,
Khoon.
In article <ln************ @nuthaus.mib.or g> Keith Thompson <ks***@mib.or g> writes: "Red Dragon" <ts*****@stream yx.com> writes:
.... /*Program to Demonstrate getchar() and scanf()*/
#include <stdio.h>
int main (void)
{
char a,b;
This is the first error. a and b should be ints.
--
dik t. winter, cwi, kruislaan 413, 1098 sj amsterdam, nederland, +31205924131
home: bovenover 215, 1025 jn amsterdam, nederland; http://www.cwi.nl/~dik/
On Fri, 21 Oct 2005 17:19:09 +0800, Red Dragon wrote:
[in reply to Keith Thompson] Incidentally, saying that getchar() has the same effect as scanf() is
meaningless without context.
I was responding to the suggestion by Kevin Bagust to try using getchar()
to solve the problem of scanf() being unable to read input character.
As I learnt from Mark McIntyre, it could not read my character input
because it was reading "newline' and jumped.
Actually the point is that it was _not_ reading newline.
This problem was
demonstrated in my exhibit program as Section 1 using getchar() and
section 2 using single scanf(), both failed to execute. Only when I
used double scanf() was the problem solved.
The dummy scanf is reading the newline (generated when you press
enter/return) that was not read by the first scanf.
[...] I see getchar() is a topic in Chapter 7.
getchar() doesn't take arguments as scanf does, it returns a value.
Your code getchar("%c",&b ); should be rewritten b = getchar();
[...] When I compiled my code as shown in my previous program, I got 0 errors
and 0 warnings.
Find out how to invoke your Visual C++ compiler in ANSI or ISO C mode
(these may be abbreviated as C89/C90/C99). In such a mode it is required
to issue a diagnostic for your code.
[...] When Tim Rentsch posted back to me what he had received, I was
horrified by the load of gibberish HTML codes I had inadvertently
created. What I had earlier done was to copy from my Visual C++ platform
and paste into Outlook Express. What I now do is to cut and paste into
Notepad, and then cut from Notepad and paste into Outlook. In this
way, I reckon I have killed all the HTML code.
Some of your posts - even those without source code - still contain HTML,
including the one to which I'm replying and its predecessor. It is
likely that Outlook is generating it - check that Plain text is still
selected for News sending on the Send tab.
-- http://members.dodo.com.au/~netocrat
Red Dragon wrote:
BTW, Do you have HTML problem with my program above?
Regards and thank you very much.
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
Keith may not see it, but I do. Weren't you given instructions on how
to set OE so it doesn't do that?
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