>double fahrenheit(double inpF)
You are returning an int, so this should be:
int fahrenheit(double inpF)
You also need to declare type in this function:
int type;
>double celcius(double inpC)
Same here.
> double input=0.0, type;
type is not a double:
int type;
> celcius(input);
This function returns the type, so:
type = celcius(input);
> fahrenheit(input);
Same here:
type = fahrenheit(input);