Most computers fall into one of the three types of architectures: Stack, Accumulator, or General Purpose Registers (GPR’s). Some computers combine features from more than one organizational structure.

The Intel 8080 microprocessor has seven CPU registers, one which is an accumulator register. As a consequence, the processor has some of the characteristics of a general register type and some of the characteristics of an accumulator type.

All arithmetic and logic instructions, as well as the load and store instructions, use the accumulator register so these instructions have only one address field. On the other hand, instructions that transfer data among the seven processor registers have a format that contains two register address fields.

The Intel 8080 processor has a stack pointer and instructions to push and pop from a memory stack. The processor, however, does not have the zero-address-type instructions which are characteristic of a stack-organized CPU.

(Information taken from Mano)

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