ARM Program Size - ZI data?

How does one interpret the code size displayed in the output window. For example my program compiled for the LPC2368:

Program Size: Code=1264 RO-data=16 RW-data=0 ZI-data=1384

1) What is ZI-Data?
2) Is RO and RW data RAM? Is it bytes or 32-bit variables? Would I add both to estimate total RAM usage?
3) I don't have any const data types, so I'm wondering how I have 16 bytes of read-only data. Is this compiler related?

Thanks for the help

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