What is the need for address and data alignment for DMA transfer?

Data alignment pertains to the starting address of some block of memory being a multiple of the basic data size, such as a 16 or 32 bit Word, or being related to the block size of an IO device, such as a disc drive with a sector size of 512 bytes. The 8085 microprocessor, itself, does not care about alignment, as it is an 8 bit computer running on an 8 bit bus. (The 8086 microprocessor does care, because misalignment can cause performance penalties or corruption, but this article deals with the 8085, not the 8086.) External devices, however, such as the 8237 DMA Controller, may well impose limitations on the starting address of a block transfer, because of their internal design. Each case is specific, so you need to consult the documentation of your specific device.