moi

// calculating the moment of inertia for different shapes

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

// prototype
float MOIx(char c, float r);
float MOIy(char c, float r);

int main(void)
{
    // creating buffers for storing the filenames for input and output files respectively
    char inp[20], out[20];
    FILE *input;
    FILE *output;

    printf("=========================\n");
    printf("CENTROIDAL MOI CALCULATOR\n");
    printf("-------------------------\n");
    printf("INPUT:\n\n\n");

    // taking input filename from user
    printf("Please enter the input file name: ");
    scanf("%s", &inp);

    // opening the file in "read" mode
    input = fopen(inp, "r");

    // checking whether the file exists
    while (input == NULL)
    {
        printf("ERROR: Input file does not exist\n");

        // prompt the user to type in the correct filename repeatedly
        printf("Please re-enter the input filename: ");
        scanf("%s", &inp);
        input = fopen(inp, "r");
    }

    // prompt the user to type in the output fileanme
    printf("Please type in the output filename: ");
    scanf("%s", &out);
    output = fopen(out, "w");



    // scanning header from the input file and printing on screen
    char header1[5], header2[7];
    fscanf(input, "%s %s\n", header1, header2);
    printf("\n%s %s %s %s\n", header1, header2, "MOIx", "MOIy");

    // printing the header for the output file
    fprintf(output, "Type Radius MOIx MOIy\n");

    char ch;
    float d;
    // creating a while loop which loops over each line until it reaches the end
    while(1)
    {
        // scanning the type and radius from input file
        fscanf(input, "%c ", &ch);
        fscanf(input, "%f\n", &d);

        // printing to the screen
        printf("%c ", ch);
        printf("%0.3e ", d);

        // printing the type and radius to the output file
        fprintf(output, "%c ", ch);
        fprintf(output, "%0.3e ", d);

        // calling the both the functions and storing the return value
        float value_MOIx = MOIx(ch, d);
        float value_MOIy = MOIy(ch, d);

        // checking for errors
        if (value_MOIx == 0 || value_MOIy == 0)
        {
            printf("INPUT ERROR\n");
            fprintf(output, "INPUT ERROR\n");
        }
        else
        {
            // printing the MOI values to screen
            printf("%0.3e ", value_MOIx);
            printf("%0.3e\n", value_MOIy);

            // printing the MOI values to output file
            fprintf(output, "%0.3e ", value_MOIx);
            fprintf(output, "%0.3e\n", value_MOIy);

        }

        // breaks out of while loop on reaching the end of the file (EOF)
        if (feof(input))
        {
            break;
        }
    }

    // closing both the files when program ends
    fclose(input);
    fclose(output);
}

// MOI about centroidal x-axis
float MOIx(char c, float r)
{
    float result;
    if (r <= 0)
    {
        // if the radius is less than equal to zero, then result is zero
        result = 0;
        return result;
    }

    else
    {
        if (c == 'A')
        {
            result = (3.142/4)*(pow(r, 4));
            return result;
        }
        else if (c == 'B')
        {
            result = ((3.142 / 8) - (8 / (9 * 3.142))) * (pow(r, 4));
            return result;
        }
        else if (c == 'C')
        {
            result = 0.5 * ((3.142 / 8) - (8 / (9 * 3.142))) * (pow(r, 4));
            return result;
        }
        else
        {
            // choosing anything other than A, B, C will give return 0
            result = 0;
            return result;
        }
    }
}

// MOI about centroidal y-axis
float MOIy(char c, float r)
{
    float result;

    // checking for input error
    if (r <= 0)
    {
        result = 0;
        return result;
    }
    else
    {
        if (c == 'A')
        {
            result = (3.142/4)*(pow(r, 4));
            return result;
        }
        else if (c == 'B')
        {
            result = (3.142/8)*(pow(r, 4));
            return result;
        }
        else if (c == 'C')
        {
            result = (3.142/8)*(pow(r, 4));
            return result;
        }
        else
        {
            // choosing anything other than A, B, C will give return 0
            result = 0;
            return result;
        }
    }
}