Thread: homework problem Please Help!

i have a homework assignment in which i am supposed to find the nominal value of a fixed resistor, given the resistor's color code. each color code has a corresponding letter and i need to make a user defined function that converts that letter to a number. the numbers for the color codes are as follows:
0 - B(Black)
1 - N(Brown)
2 - R(Red)
3 - O(Orange)
4 - Y(Yellow)
5 - G(Green)
6 - L(Blue)
7 - V(Violet)
8 - A(Gray)
9 - W(White)
-1 - D(Gold)
-2 - S(Silver)

so far i have written this much code

Code:

#include<stdio.h>
    #include<conio.h>
    #include<math.h>
    int main(){
       int dig1,dig2,dig3;
       printf("These are the color choices you have: \nBlack-B\nBrown-N\nRed-R\nOrange-O\nYellow-Y\nGreen-G\nBlue-L\nViolet-V\nGray-A\nWhite-W\nGold-D\nSilver-S\n");
       printf("Enter first color->");
       scanf("%d",&dig1);
       printf("Enter second color->");
       scanf("%d",&dig2);
       printf("Enter third color->");
       scanf("%d",&dig3);
       float
       nom=((10*dig1)+dig2)*pow(10,dig3);
       printf("The nominal resistance is %f",nom);
       getch();
       return 0;
    }

i still need the user defined function to convert the color code letters to the numbers but i have no idea what to do! please help someone!

In your function, you can use if statements or a switch as shown below:

Using if statements:

Code:

int returncode(char color)
{
    if (color=='B')
        return 0;
    if (color=='N')
        return 1;
/*and so on*/
}

Using switch:

Code:

int returncode(char color)
{
    switch(color)
    {
        case 'B':
            return 0;
        case 'N':
            return 1;
/*and so on*/
    }
}

well i put that in and i have this:

Code:

 #include<stdio.h>
    #include<conio.h>
    #include<math.h>
    int main(){
       int returncode(char color);    
       int dig1,dig2,dig3;
       printf("These are the color choices you have: \nBlack-B\nBrown-N\nRed-R\nOrange-O\nYellow-Y\nGreen-G\nBlue-L\nViolet-V\nGray-A\nWhite-W\nGold-D\nSilver-S\n");
       printf("Enter first color->\n");
       dig1=getch();
       printf("Enter second color->\n");
       dig2=getch();
       printf("Enter third color->\n");
       dig3=getch();
       float
       nom=((10*dig1)+dig2)*pow(10,dig3);
       printf("The nominal resistance is %f",nom);
       getch();
       return 0;
    }
   int returncode(char color)
{
    switch(color)
    {
        case 'B':
            return 0;
        case 'N':
            return 1;
        case 'R':
             return 2;
        case 'O':
             return 3;
        case 'Y':
             return 4;
        case 'G':
             return 5;
        case 'L':
             return 6;
        case 'V':
             return 7;
        case 'A':
             return 8;
        case 'W':
             return 9;
        case 'D':
             return -1;
        case 'S':
             return -2;
                }
}

my answers all come out as "1.#INF00" any idea?

dig1, dig2 and dig3 contain the character codes and should be converted into their respective integer values before being used in the equation:

Code:

nom=(10.0*returncode(dig1)+returncode(dig2))*pow(10.0,(double)returncode(dig3));

Also, note that getch() is not a standard C function, nor is conio.h a standard header file, so these are not portable.

so if I use this:

Code:

 #include<stdio.h>
    #include<conio.h>
    #include<math.h>
    int main(){
       int returncode(char color);
       int dig1,dig2,dig3;
       printf("These are the color choices you have: \nBlack-B\nBrown-N\nRed-R\nOrange-O\nYellow-Y\nGreen-G\nBlue-L\nViolet-V\nGray-A\nWhite-W\nGold-D\nSilver-S\n");
       printf("Enter first color->");
       scanf("%d",&dig1);
       printf("Enter second color->");
       scanf("%d",&dig2);
       printf("Enter third color->");
       scanf("%d",&dig3);
       float
       nom=(10.0*returncode(dig1)+returncode(dig2))*pow(10.0,(double)returncode(dig3));
       printf("The nominal resistance is %f",nom);
       getch();
       return 0;
    }
   int returncode(char color)
{
    switch(color)
    {
        case 'B':
            return 0;
        case 'N':
            return 1;
        case 'R':
             return 2;
        case 'O':
             return 3;
        case 'Y':
             return 4;
        case 'G':
             return 5;
        case 'L':
             return 6;
        case 'V':
             return 7;
        case 'A':
             return 8;
        case 'W':
             return 9;
        case 'D':
             return -1;
        case 'S':
             return -2;
                }
}

that gets rid of the portability problems but then after i enter the first color it prints everything after that

you are declaring the function returncode inside main. you cannot declare a function inside another function at all.

ohh yes i didnt notice that. so i changed it to:

Code:

#include<stdio.h>
    #include<conio.h>
    #include<math.h>
    int returncode(char color);
    int main(){
       int dig1,dig2,dig3;
       printf("These are the color choices you have: \nBlack-B\nBrown-N\nRed-R\nOrange-O\nYellow-Y\nGreen-G\nBlue-L\nViolet-V\nGray-A\nWhite-W\nGold-D\nSilver-S\n");
       printf("Enter first color->");
       scanf("%d",&dig1);
       printf("Enter second color->");
       scanf("%d",&dig2);
       printf("Enter third color->");
       scanf("%d",&dig3);
       float
       nom=(10.0*returncode(dig1)+returncode(dig2))*pow(10.0,(double)returncode(dig3));
       printf("The nominal resistance is %f",nom);
       getch();
       return 0;
    }
   int returncode(char color)
{
    switch(color)
    {
        case 'B':
            return 0;
        case 'N':
            return 1;
        case 'R':
             return 2;
        case 'O':
             return 3;
        case 'Y':
             return 4;
        case 'G':
             return 5;
        case 'L':
             return 6;
        case 'V':
             return 7;
        case 'A':
             return 8;
        case 'W':
             return 9;
        case 'D':
             return -1;
        case 'S':
             return -2;
                }
}

this still doesnt solve my problem. when i enter the first color it automatically prints everything else after that

Don't use %d in scanf(), because you're scanning in characters, not digits. Use %c, and put a space before it so that whitespace left from the previous input is skipped.

Code:

scanf(" %c", &var);

sounds like the old buffer bull...........
http://faq.cprogramming.com/cgi-bin/...&id=1043284392

i was finally able to get it working correctly. i am extremely thankful to everyone who has helped me for this assignment! i would not have been able to finish this without you guys!! thanks alot!!

Originally Posted by Three

you are declaring the function returncode inside main. you cannot declare a function inside another function at all.

Why not?

I'm asking because K&R 2 has many such examples. For eg, see pages 72, 120, 125 ...