function problem...

[JonathanS]

I think I asked this before, but can't find it in my posts. Feel like an idiot asking it again.

Anyways there are two if()'s. The first one is to convert degrees F to C through a function. I have already done it without functions as shown in the second if().

The problem is that the function keeps sending tempF to be 0...it seems. Tried reading it out loud what it does but the program makes sense in my head. Here is the code:

#include <stdio.h>
#include <stdlib.h>
float tempC;
float tempF;

float calcCelsius1(tempF);

int main()
{
    int choice;

    float start_temp;
    float end_temp;
    float temp_incr;




    printf("Which Temperature Scale Conversion would you like to perform?\n");
    printf("1. Convert F to C\n2. Convert C to F\n\n");

    printf("What is your choice? ");
    scanf("%d", &choice);

    if (choice == 1)
    {
        printf("\nStarting Temperature: ");
        scanf("%f", &start_temp);

        printf("Ending Temperature: ");
        scanf("%f", &end_temp);

        printf("Temperature Increment: ");
        scanf("%f", &temp_incr);


        tempF = start_temp;
        printf("\n\nFahrenheit\t\tCelsius\n");
        printf("----------\t\t-------\n");

        while(tempF<end_temp)
        {
            tempC = calcCelsius1(tempF);
            printf("TempC = %f\n", tempC);
            printf("%6.1f\t\t\t%6.1f\n", tempF, tempC);
            tempF = tempF + temp_incr;
        }
        tempF = end_temp;
        tempC = calcCelsius1(tempF);
        printf("%6.1f\t\t\t%6.1f\n", tempF, tempC);

    }

    else if (choice == 2)
    {

        printf("\nStarting Temperature: ");
        scanf("%f", &start_temp);

        printf("Ending Temperature: ");
        scanf("%f", &end_temp);

        printf("Temperature Increment: ");
        scanf("%f", &temp_incr);
        tempC = start_temp;
        printf("\n\nCelsius\t\t\tFahrenheit\n");
        printf("-------\t\t\t----------\n");

        while(tempC<end_temp)
        {
            tempF =  tempC*9/5 + 32;
            printf("%6.1f\t\t\t%6.1f\n", tempC, tempF);
            tempC = tempC + temp_incr;
        }
        tempC = end_temp;
        tempF = tempC*9/5 + 32;
        printf("%6.1f\t\t\t%6.1f\n", tempC, tempF);
    }

    else
        printf("Not a valid choice.\n");


    return 0;
}

float calcCelsius1 (tempF)
{
    tempC = (tempF - 32)*5/9;
    return tempC;
}

I finally got to fit a C++ class in my schedule for spring. So hopefully formal education on the subject will stop me coming here (asking questions that is)

[quzah]

float tempC;
float tempF;
 
float calcCelsius1(tempF);

1. You are using global variables, and as such, you don't need to pass them as arguments to a function. I'm not saying that's the best way to do it, but you don't need function arguments if you are trying to reference globals.

2. 'tempF' as a function parameter does not have a type. I would be surprised if this actually compiled. If it did, it's because it decided to default to an int. This gives you another problem, which is that you are now using a local variable called 'tempF', and as such, you aren't using your global anymore.


Quzah.

[JonathanS]

That was the problem

As always thanks for your help!

[hk_mp5kpdw]

tempF =  tempC*9/5 + 32;

...

tempC = (tempF - 32)*5/9;

Anther problem you might have is integer division. Such computations will not provide you the results you think you should be getting.

[iMalc]

In both of those, the multiplication should happen before the division, and the multiplication involves a float. So in theory that should be okay.
I don't think the compiler is allowed to pre-calculate 9/5 as 1 in this case.