Initialization to 0 of allocated arrays (of integers) is an implementation issue. i.e. do not rely on it. The low level allocation typically calls on the C malloc. Depending on the runtime system you may get it wiped or not wiped. I would suggest you wipe the allocations for your self.
Actually, the answer to your question is no, ALLOCATE is not supposed to initialize the array. I have not yet run across an implementation which does such initialization. As Jim says, you are responsible for the initialization.
The allocation would not know what initialization value to use. Wiping to 0 is not always desired. Wiping to 0 may be of interest if the cells were to then be subsequently use to accumulate totals. 0's might not be a good choice if the purpose was to provide an indication that a cell was ever used since 0 may be a valid number for use. In this case a better choice would be to initialize to a "magic number" that would seldom, if not never, be used. e.g. initializing to hexidecimal 0xBAADBEEF. Or 0x80000000 (add 0's for size of int) which is arguably -0 because it has the property of (x .eq. -x).
