1. A compiler for processing computer program source code, to generate object code to be executed by a RISC (Reduced Instruction Set Computer) type of CPU (central processing unit) of a computer, said object code including code for an instruction for judging the value of a bit variable and an instruction for assigning a value to a bit variable, said bit variables being held in a memory or a register of said computer, wherein said object code is generated such that, when said object code is executed, processing is performed whereby a bit operational expression which is written within said source code is converted to a condition judgement expression which judges the respective values of bit variables that are operands of said bit operational expression, and whereby a predetermined first binary value and a predetermined second binary value are selectively assigned to a bit variable which holds a result of said bit operational expression, in accordance with whether a “true” or a “false” decision is obtained from said condition judgement expression.