执行过程中的一个阶段所需的时间，在此期间，计算机从主存储器中取出指令或操作数，并将其存入控制器或运算器的寄存器中。

The part of execution in which an operand or instruction is read from main storage and written into a control unit or arithmetic unit register.

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它按主存储器里固定的步骤选择和检索指令，以便在适当的时刻激活系统的其它功能组件来执行相应的操作。

It selects instructions from the main memory in proper sequence and sends them to the instruction-decoding unit, which interprets them so as to activate functions of the system at appropriate moments.

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