1. An information processor comprising: a register file including a plurality of registers; an instruction execution unit utilizing said register file to execute first format instructions as native instructions; and an instruction translation circuit for translating second format instructions into said first format instructions; wherein said information processor has, when a first program described in said second format instructions is executed, a first operation mode in which said first format instructions translated by said instruction translation circuit are executed and a second operation mode in which said first format instructions translated by translation software described in said first format instructions are executed; wherein said information processor comprises a dedicated bus for transferring data between said register file and said instruction translation circuit; wherein said instruction translation circuit includes an operand output unit aligning an operand included in the first program and outputs an output signal aligned by the operand output unit directly to said register file through said dedicated bus during a transition term from said first operation mode to said second operation mode, wherein said instruction translation circuit comprises a selection circuit that includes a simulated pipeline which simulates a pipeline of said instruction execution unit and generates timing that internal information is outputted onto said dedicated bus in synchronism with a predetermined pipeline stage in said simulated pipeline and timing that said internal information on said dedicated bus is taken in; wherein a bit length of the output signal is equal to a bit length of the dedicated bus, and wherein when the operand output unit aligns the operand in the first program, the operand output unit decides which part of the output signal is to be the operand in the first program based on a bytecode length of the first program.