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October 1st, 2012, 01:21 PM

KevinFCTwente

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Join Date: Sep 2012

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Homework

My program won't work yet so I hope someone here can tell me what i've done wrong. This is my subject

Write a program that determines real roots x1 and x2 of the equation calculates, using the quadratic formula:
Reading a, b and c in. Provide appropriate text for input and output. Provide an error if b2-4ac is negative.

I hope you can correct me

Code:

#include <math.h>
 #include <stdio.h>
  
  int main()
  
 {	 	 	 	 	 	 
	/* variables */

  float A, B, C, D, x_1, x_2;
  
	/* input */
	
	/* Values for A, B and C  */
	   	  	  
printf("give value for A \n");	  	     	    
scanf("%f", A );
  
printf("give value for B \n");
scanf("%f", B );
  
printf("give value forC \n");
scanf("%f", C );
  	
/* Calculate x_1 and x_2 */
		
D = B - 4 * A * C;
   	   	   	   
  if (D>=0)
	  {
	  x_1 = -B + sqrtf(D);	
	  x_2 = -B - sqrtf(D);
		
		
/* output */
	
	printf(" x_1 \n");  	
	printf(" x_2 \n");
	
	return(0);
	  }
  else
 	  {
 	printf ("D can't be negative \n");
		
	return(0);
 	 }

}

October 1st, 2012, 01:59 PM

salem

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A couple of points.
1. Use a compiler with good diagnostics.
$ gcc -Wall foo.c -lm
foo.c: In function ‘main’:
foo.c:16:1: warning: format ‘%f’ expects argument of type ‘float *’, but argument 2 has type ‘double’ [-Wformat]
foo.c:19:1: warning: format ‘%f’ expects argument of type ‘float *’, but argument 2 has type ‘double’ [-Wformat]
foo.c:22:1: warning: format ‘%f’ expects argument of type ‘float *’, but argument 2 has type ‘double’ [-Wformat]
foo.c:9:26: warning: variable ‘x_2’ set but not used [-Wunused-but-set-variable]
foo.c:9:21: warning: variable ‘x_1’ set but not used [-Wunused-but-set-variable]
foo.c:16:6: warning: ‘A’ is used uninitialized in this function [-Wuninitialized]
foo.c:19:6: warning: ‘B’ is used uninitialized in this function [-Wuninitialized]
foo.c:22:6: warning: ‘C’ is used uninitialized in this function [-Wuninitialized]
The first 3 are telling you that you forgot the &A etc when calling scanf.

Next, good indentation will make it easier to follow your code, and also make it easier for others to understand (and help).

Code:

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

int main()
{
  /* variables */
  float A, B, C, D, x_1, x_2;

  /* input */
  /* Values for A, B and C  */
  printf("give value for A \n");
  scanf("%f", A);

  printf("give value for B \n");
  scanf("%f", B);

  printf("give value forC \n");
  scanf("%f", C);

  /* Calculate x_1 and x_2 */
  D = B - 4 * A * C;

  if (D >= 0) {
    x_1 = -B + sqrtf(D);
    x_2 = -B - sqrtf(D);

    /* output */
    printf(" x_1 \n");
    printf(" x_2 \n");
    return (0);
  } else {
    printf("D can't be negative \n");
    return (0);
  }

}

There are a couple of other mistakes as well, but that should at least get you running.

__________________
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October 13th, 2012, 07:47 AM

Cornel1923

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Join Date: Oct 2012

Posts: 1

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a program for cryptography

Hello..
i really need a little help

...i want to do a program that make cryptography substitution...i know what i have to do ,but i am a little weak at programming....ok..my problem is when i want to copy a file in another file(this is simple) ,but in the 2nd file i want to have only the characters ..whitout spaces or comma or dots....just characters...forward i think i know what i have to do ,but here is my problem...this is what i did.:
#include<stdio.h>
int main(){
FILE *p,*q;
char file1[20],file2[20];
char ch;
printf("\nEnter the source file name to be copied:");
gets(file1);
p=fopen(file1,"r");
if(p==NULL){
printf("cannot open %s",file1);
exit(0);
}
printf("\nEnter the destination file name:");
gets(file2);
q=fopen(file2,"w");
if(q==NULL){
printf("cannot open %s",file2);
exit(0);
}
while((ch=getc(p))!=EOF)
putc(ch,q);
printf("\nCOMPLETED");
fclose(p);
fclose(q);

char *txt;
txt=&ch;
int i,count=1;

for(i=0;i<=count;i++);
printf("\n\nSunt %d de caractere \n\n",txt);

getch();

}

...i don't know how to copy only the characters ,..and ye...how to convert them..from uppercase to lowercase but this i can do to the second file..thx..

October 13th, 2012, 08:05 AM

hamed.samie

Registered User

Join Date: Oct 2012

Posts: 6

Time spent in forums: 1 h 19 m 18 sec
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myfopen()

Hello every body,

I want to write a function myfopen()

int* myfopen(const char*, const char)

that works like fopen() but i must write this function without using <STDIO.h>

I dont have any idea, Can you plz help me?

Thanks

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