Question

Write a C++ program to determine the value of resistance based on its color code.

Using Arrays.

In C++ only.

Answer 1

CODE

#include <iostream>

#include <cstring>

using namespace std;

#define nItems (sizeof item_list/sizeof *item_list)

char status = 'Y';

//

enum {MINC = 3, MAXCC = 10};

// resister bands

enum resistor_band_items {BLACK, BROWN, RED, ORANGE, YELLOW, GREEN,

BLUE, VIOLET, GRAY, WHITE, UNKNOWN};

struct items

{

char *name;

enum resistor_band_items id;

} item_list[] = {

{"black", BLACK},

{"brown", BROWN},

{"red", RED},

{"orange", ORANGE},

{"yellow", YELLOW},

{"green", GREEN},

{"blue", BLUE},

{"violet", VIOLET},

{"gray", GRAY},

{"white", WHITE}

};

unsigned int multiplier[] = {1, 10, 100, 1000, 10000, 100000, 1000000,

10000000, 100000000, 1000000000};

int srchItems (char *ccode); //a search for index values

char *strcpy2lower (char *dest, char *src); //converts to lower case

int scmp (char *a, char *b); //simple string comarison

char *sepnumber (char *s, long val); //puts space every 3rd digit

int main(void)

{

int i, error = 0, mult;

char input[MINC][MAXCC]; //user input

char invalid[MINC][MAXCC]; // invalid enteries

int colour_val[MINC]; //stores the band value

long total_resistance = 0;

char resistor_value_string[20] = "";//formatted output

do

{

//prompt user

printf("%s\n%s\n%s\n",

"Enter the colours of the resistor's three bands,",

"beginning with the band nearest to the end.",

"Type the colours in lowercase letters only, NO CAPS.");

for (i = 0; i < MINC; ++i)

{

printf("Band %d => ", i + 1); // print headers for each band

scanf(" %s", &input[i]); // get the user input

// converts user input to index of colours

colour_val[i] = srchItems(input[i]);

}

for (i = 0; i < MINC; ++i)

{

if (colour_val[i] == -1)

{

strcpy(invalid[i], input[i]);

error++;

}

}

if (error > 0)

{

if (error == 1)

{

printf("Invalid colour: %s\n", invalid[0]);

}

else if (error == 2)

{

printf("Invalid colours: %s, %s\n", invalid[0], invalid[1]);

}

else

{

printf("Invalid colours: %s, %s, %s\n",

invalid[0], invalid[1], invalid[2]);

}

}

else

{

//

for (i = 0; i < MINC - 1; ++i)

{

total_resistance = (total_resistance * 10) + colour_val[i];

}

mult = colour_val[2];

total_resistance *= multiplier[mult];

sepnumber (resistor_value_string, total_resistance);

printf("Resistance value: %s -Ohms\n", resistor_value_string);

//debug

for (i = 0; i < MINC; ++i)

{

//printf("Input ==> %s\t", input[i]);

//printf("index ==> %d\n", colour_val[i]);

}

//end debug

}

error = 0;

total_resistance = 0;

for (i = 0; i < MINC; ++i)

{

colour_val[i] = 0;

}

//ask user if they want to continue

printf("Do you want to decode another resistor?\n");

scanf(" %c", &status);

if (status == 'Y');

else break;

} while (status == 'Y');

return 0;

}

int srchItems (char *ccode)

{

int i;

char lccode [MAXCC] = "";

strcpy2lower (lccode, ccode); // converts everything to lower case

for (int i = 0; i < (int)nItems; ++i)

if (*lccode == *(item_list[i].name))

if (!scmp(item_list[i].name, lccode))

return i;

return -1;

}

char *strcpy2lower (char *dest, char *src)

{

if (!src || !dest) return NULL;

char *d = dest;

for (; *src; src++, d++)

if ('A' <= *src && *src <= 'Z')

*d = *src | (1 << 5);

else

*d = *src;

*d = 0;

return dest;

}

int scmp (char *a, char *b)

{

if (!a && !b) return 0;

if ( a && !b) return 1;

if (!a && b) return -1;

for (; *a && *b && *a == *b; a++, b++) {}

return *a - *b;

}

/** separate long value every 3rd char into 's' */

char *sepnumber (char *s, long val)

{

char numstr[3 * MAXCC] = "";

char *p = numstr;

size_t idx = 0, len = 0;

sprintf (numstr, "%ld", val);

for (; *p; p++) {}

len = p - numstr;

//printf("%d\n", len);

p = s + 3 * MAXCC - 2;

while (len--) {

if (idx++ == 3) {

idx = 1;

*p-- = ' ';

}

*p = numstr[len];

if (len) p--;

}

for (idx = 0; *p; p++, idx++) s[idx] = *p; /* copy to s */

s[idx] = *p; /* nul-terminate */

return s;

}

NOTE: Please ignore the warning messages. They are coming because I am using printf() for better readability.