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What does the following assembly language instruction do?

addu $t5,$zero,$t7

Answer:

It copies the contents of register $t7 into register $t5.


Pseudoinstructions

The addu instruction, used as above with register $zero, copies a bit pattern from the source register into the destination register. This is usually called a move operation, although the source register does not change. It is often convenient to move a value from one register to another.

It is awkward to say "add" when you mean "move". The extended assembler allows you to use the mnemonic move instead of addu. This mnemonic does not correspond to a new machine instruction. It is just a way of asking for the same instruction by using a more intuitive mnemonic. It is a pseudoinstruction that the assembler translates into the appropriate basic assembly instruction.

A pseudoinstruction is an instruction that the extended assembler replaces with one or more basic assembly instructions.

The extended assembler implements many pseudoinstructions. Sometimes they are just convenient re-naming of basic assembly instructions. Other times they correspond to a small, convenient sequence of basic assembly instructions. Here is the move pseudoinstruction:

move d,s        #  copy the contents of 
                #  the source register s
                #  to the destination register d
                #  (pseudoinstruction)

The registers d and s can be specified by using register mnemonic names (such as $t5 or $zero) or by using register numbers (such as $13 or $0). This is true for all instructions of the extended assembler.


QUESTION 6:

Write the instruction that moves (copies) the contents of register $t3 into register $s1.

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