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A register is loaded from memory.

Load and Store

The operands for all arithmetic and logic operations are contained in registers. To operate on data in main memory, the data is first copied into registers.

A load operation copies data from main memory into a register. A store operation copies data from a register into main memory .

When a word (4 bytes) is loaded or stored the memory address must be a multiple of four. This is called an alignment restriction. Addresses that are a multiple of four are called word aligned. This restriction makes the hardware simpler and faster.

The lw instruction loads a word into a register from memory.

The sw instruction stores a word from a register into memory.

Each instruction specifies a register and a memory address (details in a few pages).


Which of the following addresses are word aligned?

Hint: how can you multiply by four in binary?

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