//=========================================================================
#define PROGRAMMER "BAHN, William"
#define PROG_CODE  "bahw"
#define COURSE     "ECE-1021"
#define YEAR       (2003)
#define TERM       "Fall"
#define SECTION    (0)
#define ASSIGNMENT "RWA 5.4"
#define REVISION   (0)
#define TITLE      "Real World Application from Section 5.4"
#define SUBTITLE   "Computing Resistance"
#define EMAIL      "wbahn@eas.uccs.edu"
#define FILENAME   "rwa0504.c"
//=========================================================================

// PROBLEM:
//
// MODIFIED FROM TEXT
//
// Given single-character codes for the colored bands that mark a resistr,
// compute and display the resistance. Print the value in engineering
// notation using the proper prefixes for the unit of resistance (ohms).
//
// Note that the characters in this program are slightly different
// than the section in the book.
//
// Color    Character  Value  Multiplier Tolerance
// Black        K        0      10^0         -
// Brown        B        1      10^1         1%
// Red          R        2      10^2         2%
// Orange       O        3      10^3         -
// Yellow       Y        4      10^4         -
// Green        G        5      10^5         -
// Blue         U        6      10^6         -
// Violet       V        7      10^7         -
// Gray         A        8      10^8         -
// White        W        9      10^9         -
// Gold         D        -      10^-1        5%
// Silver       S        -      10^-2       10%
// None         N        -       --         20%
//
// The resistors can have three, four, or five bands.
//
// Three bands:
//     R = [10^(1st band) + (2nd band)] * 10^(3rd band)
//     Tolerance = 20%
// Four bands:
//     R = [10^(1st band) + (2nd band)] * 10^(3rd band)
//     Tolerance = (fourth band) (must be silver or gold)
// Five bands:
//     R = [100^(1st band) + 10*(2nd band) + (3rd band)] * 10^(4th band)
//     Tolerance = (fifth band) (must be red or brown)
//
// Engineering notation generally expresses a value as:
//
//   (mantissa) * 10^(exponent)
//
// where 1 <= mantissa < 1000
// and |(exponent)| is evenly divisible by 3.
//
// Furthermore, the multipler portion [ * 10^(exponent) ] is generally
// replaced with a prefix as follows:
//
//     10^-24  yocto (y)
//     10^-21  zepto (z)
//     10^-18  atto  (a)
//     10^-15  femto (f)
//     10^-12  pico  (p)
//     10^-9   nano  (n)
//     10^-6   micro (u) (or the Greek letter mu if feasible)
//     10^-3   milli (m)
//     10^0    (none)
//     10^3    kilo  (k)
//     10^6    mega  (M)
//     10^9    giga  (G)
//     10^12   tera  (T)
//     10^15   peta  (P)
//     10^18   exa   (E)
//     10^21   zetta (Z)
//     10^24   yotta (Y)
//
// The largest value of resistance that can be represented by any of
// these codes is: 999x10^9 or 999 gigaohms.
//
// The smallest value of resistance that can be represented by any of
// these codes is: 01x10^-2 or 10 milliohms.
//
// PSEUDOCODE
//
// 1) REM: Get the five character-codes from the user.
//         Store them in five different variables.
//         Store 'N' for codes not entered if less than five codes.
// 2) REM: Determine the resistor value
// 3) REM: Scale to engineering notation
// 4) REM: Determine the prefix to print
// 5) REM: Determine the tolerance
//
// Without the use of arrays, getting the five codes is a bit tricky
// since the user may enter 3, 4, or 5 characters.
//
// This lends itself to a switch() statement
//


//== INCLUDE FILES ========================================================
#include <stdio.h> // printf(), scanf()
#include <math.h>  // pow()
//== FUNCTION PROTOTYPES ==================================================
void PrintHeader(void);
void PrintCodes(void);
void GetCodes(char *b1, char *b2, char *b3, char *b4, char *b5);
double GetResistance(char b1, char b2, char b3, char b4, char b5);
int GetTolerance(char b1, char b2, char b3, char b4, char b5);
void PrintColors(char b1, char b2, char b3, char b4, char b5);
void PrintValue(double r, int tol);

//== MAIN FUNCTION ========================================================
int main(void)
{
	char band1, band2, band3, band4, band5;
	double r;
	int tol;

	PrintHeader();
	printf("\n"); // Print a blank line

	PrintCodes();
	GetCodes(&band1, &band2, &band3, &band4, &band5);
	r = GetResistance(band1, band2, band3, band4, band5);
	tol = GetTolerance(band1, band2, band3, band4, band5);
	PrintColors(band1, band2, band3, band4, band5);
	PrintValue(r, tol);

	return(0);
}

//== SUPPORT FUNCTIONS ====================================================
void PrintHeader(void)
{
	printf("========================================"
			 "=======================================\n");
	printf("Course....... %s-%i (%s %i)\n", COURSE, SECTION, TERM, YEAR);
	printf("Programmer... %s (%s)\n", PROGRAMMER, PROG_CODE);
	printf("Assignment... %s (Rev %i) (Source Code in %s)\n",
		ASSIGNMENT, REVISION, FILENAME);
	printf("Description.. %s\n", TITLE);
	printf("              %s\n", SUBTITLE);
	printf("========================================"
			 "=======================================\n");

	return;
}

void PrintCodes(void)
{
printf("   Color    Character  Value  Multiplier Tolerance\n");
printf("   Black        K        0      10^0         -    \n");
printf("   Brown        B        1      10^1         1%   \n");
printf("   Red          R        2      10^2         2%   \n");
printf("   Orange       O        3      10^3         -    \n");
printf("   Yellow       Y        4      10^4         -    \n");
printf("   Green        G        5      10^5         -    \n");
printf("   Blue         U        6      10^6         -    \n");
printf("   Violet       V        7      10^7         -    \n");
printf("   Gray         A        8      10^8         -    \n");
printf("   White        W        9      10^9         -    \n");
printf("   Gold         D        -      10^-1        5%   \n");
printf("   Silver       S        -      10^-2       10%   \n");
printf("   None         N        -       --         20%   \n");
	printf("========================================"
			 "=======================================\n");

	return;
}

void GetCodes(char *b1, char *b2, char *b3, char *b4, char *b5)
{
	char c;
	int n;

	n=1;
	c = 0;

	printf("Enter the code for each band on the resistor: ");

	while(n<=5)
	{
		scanf("%c", &c);
		switch(c)
		{
			case '\n':
				switch(n)
				{
					case 1:	*b1 = 'N';
								n++;
					case 2:	*b2 = 'N';
								n++;
					case 3:	*b3 = 'N';
								n++;
					case 4:	*b4 = 'N';
								n++;
					case 5:	*b5 = 'N';
								n++;
				}
				break;
			default:
				switch(n)
				{
					case 1:	*b1 = c; break;
					case 2:	*b2 = c; break;
					case 3:	*b3 = c; break;
					case 4:	*b4 = c; break;
					case 5:	*b5 = c; break;
				}
				n++;
		}
	}
	return;
}

int GetValue(char color)
{
	switch(color)
	{
		case 'K': return(0);
		case 'B': return(1);
		case 'R': return(2);
		case 'O': return(3);
		case 'Y': return(4);
		case 'G': return(5);
		case 'U': return(6);
		case 'V': return(7);
		case 'A': return(8);
		case 'W': return(9);
		case 'D': return(-1);
		case 'S': return(-1);
		case 'N': return(-1);
	}
	return(-99);
}

int GetMultiplier(char color)
{
	switch(color)
	{
		case 'D': return(-2);
		case 'S': return(-1);
		default : return(GetValue(color));
	}
}

double GetResistance(char b1, char b2, char b3, char b4, char b5)
{
	double r;

	r = 10.0*GetValue(b1) + GetValue(b2);
	if('N' == b5)
	{
		r *= pow(10.0, GetMultiplier(b3));
	}
	else
	{
		r = 10.0 * r + GetValue(b3);
		r *= pow(10.0, GetMultiplier(b4));
	}
	return(r);
}

int GetTolerance(char b1, char b2, char b3, char b4, char b5)
{
	// NOTE: Warnings may be issued because b1, b2, and b3 are not
	// actually used in the function.
	int tol;

	switch(b5)
	{
		case 'B': tol = 1; break;
		case 'R': tol = 2; break;
		case 'N': switch(b4)
					 {
						case 'D': tol = 5;  break;
						case 'S': tol = 10; break;
						case 'N': tol = 20; break;
					 }
	}

	return(tol);
}

void PrintColors(char b1, char b2, char b3, char b4, char b5)
{
	int n;
	char color;

   printf("Resistor Band Colors:\n");
	for(n = 1; n <= 5; n++)
	{
		printf("    Band %1i:", n);
		switch(n)
		{
			case 1: color = b1; break;
			case 2: color = b2; break;
			case 3: color = b3; break;
			case 4: color = b4; break;
			case 5: color = b5; break;
		}
		printf(" (%c) ",color);              
		switch(color)
		{
			case 'K': printf("Black"); break;
			case 'B': printf("Brown"); break;
			case 'R': printf("Red"); break;
			case 'O': printf("Orange"); break;
			case 'Y': printf("Yellow"); break;
			case 'G': printf("Green"); break;
			case 'U': printf("Blue"); break;
			case 'V': printf("Violet"); break;
			case 'A': printf("Gray"); break;
			case 'W': printf("White"); break;
			case 'D': printf("Gold"); break;
			case 'S': printf("Silver"); break;
			case 'N': printf("NONE"); break;
		}
		printf("\n");
	}
	return;
}

void PrintValue(double r, int tol)
{
	int steps;

	printf("Resistor Value: ");
	steps = 0;

	if(1.0 > r)
	{
		r *= 1000.0;
		steps--;
	}

	while(1000.0 < r)
	{
		r /= 1000.0;
		steps++;
	}

	printf("%7.2f",r);

	switch(steps)
	{
		case -1: printf(" milliohms"); break;
		case  0: printf(" ohms"); break;
		case  1: printf(" kilohms"); break;
		case  2: printf(" megohms"); break;
		case  3: printf(" gigohms"); break;
	}

	printf(" (%i%%)\n", tol);
	return;
}