Thread: Help with a resistor decoder

I am currently working a program that is supposed to decode a six banded resistor, but every time I run the program it tells me that I have entered an invalid color, and the compiler also gives me a warning that I have parameter names (without types) in function declaration.

Here is the code. Any help would be greatly appreciated.

Code:

#include<stdio.h>
#include<conio.h>
#include<stdbool.h>
#include<string.h>
bool color_check(char (*col)[7], const char (*r_col)[7]);
void get_resistance(char (*col)[7], const char (*r_col)[7]);
void get_tolerance(char (*col)[7], const char (*r_col)[7]);
void get_tempco(char (*col)[7], const char (*r_col)[7]);
char ch;

int main(void)
{
do{
    char col[6][7];
    const char r_col[12][7]={"silver","gold","black","brown","red","orange","yellow","green","blue","violet","grey","white"};
    
    input:
    printf("\t\t*****Resistor Calculator*****\n");
    printf("Please enter the color of the six bands seperated by a space.\n");
    scanf("%s %s %s %s %s %s", &col[0], &col[1], &col[2], &col[3], &col[4], &col[5]);
    
    printf("%s %s %s %s %s %s", col[0], col[1], col[2], col[3], col[4], col[5]);
    
    if(color_check(col, r_col))
    {
      void get_resistance(col, r_col);
      void get_tolerance(col, r_col);
      void get_tempco(col, r_col);
    }
    else
    {
      printf("You have entered an invalid color. Please try again");
      goto input;
    }


}while(ch == 'Y' || ch == 'y');
    return 0;
}

bool color_check(char (*col)[7], const char (*r_col)[7])
{
  int i, j;
  
  for(i = 0; i < 12; i++)
  {
        for(j = 0; j < 7; j++)
        {
              if(strncmp(col[j], r_col[i], 7) != 0)
              {
              return false;
              }
        }
  }
  
    if((strncmp(col[0], r_col[2], 7) == 0)||(strncmp(col[0], r_col[1], 7) == 0)||(strncmp(col[0], r_col[0], 7) == 0))
    { 
       return false; 
    }
    else if((strncmp(col[1], r_col[1], 7) == 0)||(strncmp(col[1], r_col[0], 7) == 0)||(strncmp(col[2], r_col[1], 7) == 0)||(strncmp(col[2], r_col[0], 7) == 0))
    {
       return false; 
    }
    else if(strncmp(col[4], r_col[11], 7) == 0) 
    { 
       return false; 
    }
    else if((strncmp(col[5], r_col[7], 7) == 0)||(strncmp(col[5], r_col[10], 7) == 0)||(strncmp(col[5], r_col[11], 7) == 0)||(strncmp(col[5], r_col[1], 7) == 0)||(strncmp(col[5], r_col[0], 7) == 0))
    { 
       return false; 
    }
    else
    {
       return true;
    }       
}

void get_resistance(char (*col)[7], const char (*r_col)[7])
{
    int i;
    double color_pts, resist, exp;
    
    for(i=0; i<4; i++)
    {
      if (strncmp(col[i], r_col[0], 7) == 0 ) 
      { 
        color_pts = -2; 
        exp = .01; 
      }
       else if (strncmp(col[i], r_col[1], 7) == 0 )
       { 
         color_pts = -1;
         exp = .1;
       }
       else if (strncmp(col[i], r_col[2], 7) == 0 ) 
       { 
         color_pts = 0;
         exp = 1;
       }
       else if (strncmp(col[i], r_col[3], 7) == 0 )
       { 
         color_pts = 1;
         exp = 10;
       }
       else if (strncmp(col[i], r_col[4], 7) == 0 )
       { 
         color_pts = 2;
         exp = 100;
       } 
       else if (strncmp(col[i], r_col[5], 7) == 0 )
       { 
         color_pts= 3;
         exp = 1000;
       }
       else if (strncmp(col[i], r_col[6], 7) == 0 ) 
       {
         color_pts;
         exp = 10000;
       }
       else if (strncmp(col[i], r_col[7], 7) == 0 )
       { 
         color_pts = 5;
         exp = 100000;
       }
       else if (strncmp(col[i], r_col[8], 7) == 0 ) 
       {
         color_pts = 6;
         exp = 1000000;
       }
       else if (strncmp(col[i], r_col[9], 7) == 0 ) 
       { 
         color_pts = 7;
         exp = 10000000;
       }
       else if (strncmp(col[i], r_col[10], 7) == 0 )
       {
         color_pts = 8;
         exp = 100000000;
       }
       else if (strncmp(col[i], r_col[11], 7) == 0 )
       { 
         color_pts = 9;
         exp = 1000000000;
       }
       
       if(i == 0)
       { 
         resist = color_pts * 100; 
       } 
       if(i == 1)
       { 
         resist += color_pts * 10;
       } 
       if(i == 2)
       { 
         resist += color_pts;
       }
       if(i == 3)
       {
         resist = color_pts * exp;
       }
    }   

  if(resist < 1000000)
  { 
    printf("Resistance = %.2f kOhms\n", resist/1000);
  }
  else 
  { 
    printf("Resistance = %.2f MOhms\n", resist/1000000); 
  }
}

void get_tolerance(char (*col)[7], const char (*r_col)[7])
{
     double tolerance;
    
    if(strncmp(col[4], r_col[3], 7) == 0)
    { 
      tolerance = 1; 
    }
    else if(strncmp(col[4], r_col[4], 7) == 0)
    {
      tolerance = 2;
    }
    else if(strncmp(col[4], r_col[5], 7) == 0)
    { 
      tolerance = 3;   
    }
    else if(strncmp(col[4], r_col[6], 7) == 0)
    { 
      tolerance = 4; 
    }
    else if(strncmp(col[4], r_col[7], 7) == 0)
    {
      tolerance = .5; 
    }
    else if(strncmp(col[4], r_col[8], 7) == 0)
    {
      tolerance = .25; 
    }
    else if(strncmp(col[4], r_col[9], 7) == 0)
    {
      tolerance = .1;
    }
    else if(strncmp(col[4], r_col[10],7) == 0)
    {
      tolerance = .05; 
    }
    else if(strncmp(col[4], r_col[1], 7) == 0)
    { 
      tolerance = 5;   
    }
    else if(strncmp(col[4], r_col[0], 7) == 0)
    { 
      tolerance = 10; 
    }
     
    printf("Tolerance = +/- %.2g%%\n", tolerance);
}

void get_tempco(char (*col)[7], const char (*r_col)[7])
{
     int tempco;
     
     if(strncmp(col[5], r_col[3], 7) == 0)
     {
       tempco = 100;
     }
     else if(strncmp(col[5], r_col[4], 7) == 0)
     {
       tempco = 50;
     }
     else if(strncmp(col[5], r_col[5], 7) == 0)
     {
       tempco = 15;
     }
     else if(strncmp(col[5], r_col[6], 7) == 0)\
     { 
       tempco = 25;
     }
     else if(strncmp(col[5], r_col[8], 7) == 0)
     {
       tempco = 10;
     }
     else if(strncmp(col[5], r_col[9], 7) == 0)
     {
       tempco = 5;
     }     
     printf("Tempco = %d ppm/degreeC\n", tempco);
}

Syntax error:

Code:

    if(color_check(col, r_col))
    {
      void get_resistance(col, r_col);
      void get_tolerance(col, r_col);
      void get_tempco(col, r_col);
    }
    else
    {
      printf("You have entered an invalid color. Please try again");
      goto input;

When you call a function you shouldn't prefix the call with the return type. You shouldn't have "void" in there.


The colour checking code....

Code:

  for(i = 0; i < 12; i++)
  {
        for(j = 0; j < 7; j++)
        {
              if(strncmp(col[j], r_col[i], 7) != 0)
              {
              return false;
              }
        }
  }

If I am reading this right, you're trying to just confirm that the input was actually a valid colour string. This doesn't work. For example, say the first colour I put in was "white". Then r_col[i] is "silver" the first time through the loop. The strncmp fails and the whole function returns false.

You need to only return false if a colour is really invalid. You could do this by having having an extra variable to record whether or not the colour is valid.

I think this should do it:

Code:

    bool col_valid = true;

    for(j = 0; j < 7; j++)
	{
		if (!col_valid)
			return false;
		col_valid = false;
		for(i = 0; i < 12; i++)
		{
			if(strncmp(col[j], r_col[i], 7) == 0)
			{
				col_valid = true;
				break;
			}
		}
	}

oh - I didn't get any warnings about missing types in declarations. Different compiler versions I guess.

Also learn about loops... goto is a leftover from the old days of BASIC that has little or no real use in modern programming.

Originally Posted by smokeyangel

oh - I didn't get any warnings about missing types in declarations. Different compiler versions I guess.

Turn the warning level on your compiler up to maximum... and treat all warnings as errors to be fixed.

Cool, it validates colors correctly now. CommonTater, you are a boss. Thank you.