A software debugger tangibly embodied on a computer readable medium may display a microcomputer program being debugged so that a halt address at which the execution of the program is caused to halt can be distinguished from other addresses. When performing step-by-step execution of the program, a determination is made whether an instruction at the halt address is a predicate execution instruction or not. If the instruction is a predicate execution instruction, a condition flag value for the instruction is acquired. Based on the condition flag value, a determination is made whether the predicate execution instruction is to be executed or not. Then, the instruction at the halt address is displayed on a screen by changing a display method according to the result of the determination.