'C' Pre-processor implementation

Projects Interfacing w/ Software on the Computer
1

I like to use #defines to do simple arthmetic for me i.e.

#define NUM_DAYS 7
#define HOURS_IN_DAY 24
#define HOURS_IN_WEEK (NUM_DAYS * HOURS_IN_DAY)

but it doesn't work.
How much of the 'C' pre-processor is implemented in Arduino?

2

In what way doesn't it work?

3

Sorry, the fault was elsewhere.