Which of the following addresses a portion of the primary memory by specifying the actual address of the memory location?

Which of the following addresses a portion of the primary memory by specifying the actual address of the memory location?
A .  direct addressing
B .  Indirect addressing
C .  implied addressing
D .  indexed addressing

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Answer: A

Explanation: Absolute/Direct

+——+—–+————————————–+

| load | reg | address |

+——+—–+————————————–+

(Effective address = address as given in instruction)

This requires space in an instruction for quite a large address. It is often available on CISC machines which have variable-length instructions, such as x86.

Some RISC machines have a special Load Upper Literal instruction which places a 16-bit constant in the top half of a register. An OR literal instruction can be used to insert a 16-bit constant in the lower half of that register, so that a full 32-bit address can then be used via the register-indirect addressing mode, which itself is provided as "base-plus-offset" with an offset of 0.

http://en.wikipedia.org/wiki/Addressing_mode (Very good coverage of the subject)

also see: Source: KRUTZ, Ronald L. & VINES, Russel D., The CISSP Prep Guide: Mastering the Ten Domains of Computer Security, page 186. also see: http://www.comsci.us/ic/notes/am.html