>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);