Thread: New coder, simple help please.

I am completely new to C programming, so please go easy on the jargon, but I do accept all criticism.

I want to make a code that solves a solution to any quadratic ax^2+bx+c. I made an attempt at it, but of course I came short with many errors.

Code:

#include <stdio.h>
#include <math.h>

int main(void) {
    float x,a,b,c;

    printf("Enter your values of a b c that correspond to the quadratic
ax^2+bx+c: ", a, b, c);
    scanf("%f %f %f", &a, &b, &c);

        x = (-b + sqrt(b*b-4*a*c))/(2*a);

        if (b*b >= 4*a*c) {
                printf("A solution to your quadratic is:%f\n",x);
        else
                printf("There are no real solutions to your
quadratic\n");
}
return 0;
}

Thank you!

Thanks for the reply claudiu.

This is for school and I wasn't required to give both solutions, but I guess there's no harm in it. This is what I have now after trying to implement your suggestions:

Code:

#include <stdio.h>
#include <math.h>

int main(void) {
    float x1,x2,a,b,c;

    printf("Enter your values of a b c that correspond to the quadratic
ax^2+bx+c: \n);
    scanf("%f %f %f", &a, &b, &c);

        if (b*b - 4*a*c >= 0) {
                x1 = (-b + sqrt(b*b-4*a*c))/(2*a);
                x2 = (-b - sqrt(b*b-4*a*c))/(2*a);
                printf("The solutions to your quadratic are:%f %f
\n",x1,x2);
        else
                printf("There are no real solutions to your
quadratic\n");
}
return 0;
}

Looks good to me. Is it working properly?

Sadly, no
I get a LOT of errors...

Code:

quadratic.c:7:12: error: missing terminating " character
quadratic.c: In function 'main':
quadratic.c:7: error: missing terminating " character
quadratic.c:8: error: 'ax' undeclared (first use in this function)
quadratic.c:8: error: (Each undeclared identifier is reported only once
quadratic.c:8: error: for each function it appears in.)
quadratic.c:8: error: 'bx' undeclared (first use in this function)
quadratic.c:8: error: expected ')' before ':' token
quadratic.c:8: error: stray '\' in program
quadratic.c:14:10: error: missing terminating " character
quadratic.c:14: error: missing terminating " character
quadratic.c:15: error: stray '\' in program
quadratic.c:15:3: error: missing terminating " character
quadratic.c:15: error: missing terminating " character
quadratic.c:15: error: 'n' undeclared (first use in this function)
quadratic.c:16: error: expected ')' before 'else'
quadratic.c:17:10: error: missing terminating " character
quadratic.c:17: error: missing terminating " character
quadratic.c:18: error: stray '\' in program
quadratic.c:18:12: error: missing terminating " character
quadratic.c:18: error: missing terminating " character
quadratic.c:21: error: expected ';' before '}' token
quadratic.c:21: error: expected declaration or statement at end of input

Oh yeah I missed that one ". I don't understand what the other errors mean though: for e.g.

expected ';' before '}' token

What does it mean by "it expected" those? Does it mean I'm missing a ; before the } or something?

I've changed my code to this so far:

Code:

#include <stdio.h>
#include <math.h>

int main(void) {
    float x1,x2,a,b,c;

    printf("Enter your values of a b c that correspond to the quadratic
ax^2+bx+c: \n");
    scanf("%f %f %f", &a, &b, &c);

        if (b*b - 4*a*c >= 0) {
                x1 = (-b + sqrt(b*b-4*a*c))/(2*a);
                x2 = (-b - sqrt(b*b-4*a*c))/(2*a);
                printf("The solutions to your quadratic are:%f %f
\n",x1,x2) }
        else
                printf("There are no real solutions to your
quadratic\n");

return 0;
}

But I still seem to keep getting a lot of missing terminating " character. I don't know where I'm missing them...

Oh thanks for that! The hundred errors are reduced to two now:

Code:

quadratic.c: In function 'main':
quadratic.c:15: error: expected ';' before '}' token

I'm using Putty and the code would jump to the next line on its own, unlike notepad which can have a line thousands of characters long.

Let me refresh. I think I fixed that error that says: expected ';' before '}' token

So this is the code I have so far:

Code:

#include <stdio.h>
#include <math.h>

int main(void) {
    float x1,x2,a,b,c;

    printf("Enter your values of a b c that correspond to the"
"quadratic ax^2+bx+c: \n");
    scanf("%f %f %f", &a, &b, &c);

        if (b*b - 4*a*c >= 0) {
                x1 = (-b + sqrt(b*b-4*a*c))/(2*a);
                x2 = (-b - sqrt(b*b-4*a*c))/(2*a);
                printf("The solutions to your quadratic are:%f %f"
"\n",x1,x2); }
        else
                printf("There are no real solutions to your"
"quadratic\n");

return 0;
}

And when I try and compile it with:

Code:

gcc -Werror -Wall -O -o quadratic quadratic.c

I get these errors:

Code:

/tmp/ccykv6lI.o: In function `main':
quadratic.c:(.text+0x81): undefined reference to `sqrt'
quadratic.c:(.text+0xc1): undefined reference to `sqrt'
collect2: ld returned 1 exit status

I remember in school they told us to add -ml for math library when using #include <math.h> but when I do this as so:

Code:

gcc -Werror -Wall -ml -O -o quadratic quadratic.c

It says it doesn't recognize -ml.

Originally Posted by laserlight

You have a brace for your if statement that is not properly matched by a closing brace. To match it, introduce a closing brace before the else keyword, and then an opening brace after it.

Is it necessary to have braces around the else part if it's just one line of code?

Originally Posted by laserlight

I am not sure what is the problem, but it is likely that neither PuTTY nor the text editor that you use is imposing a line limit.

As I was typing in PuTTY it reached the end of the screen and jumped to the next line. That is where the problem arose.
As long as I know a way to counter-act this, I'm happy

Originally Posted by laserlight

-lm

Haha such a simple mistake.

Thank you so much! My program works now!

I'll keep that in mind.