I had been using 8051 controllers, which have several general purpose bits in the RAM that can be set, cleared and tested for conditional loops. In the AVR series (specially Atmega 64/128) such bits are not available. In order to have flags the only method I see is to reserve a complete byte in RAM of AVR. Other bits of this byte may be used as other flags, but the code increases. Is there any method of having such user defined flags, which can be set/reset etc, with very less code?