Microprocessor
A sequence of two registers that multiplies the content of DE register pair by two and stores the result in HL register pair (in 8085 assembly language) is

 XTHL & DAD H
 XCHG & DAD H
 PCHL & DAD D
 XCHG & DAD B

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Microprocessor
A good assembly language programmer should use general purpose registers rather than memory in maximum possible ways for data processing. This is because:

 Of limited set of instructions for data processing with memory
 Data processing with registers takes fewer cycles than that with memory
 Data processing with registers is easier than with memory
 Data processing with memory requires more instructions in the program than that with registers

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