1. A converting method for converting an architecture of a program, comprising: a first step of compiling a first high-level language source program for a computer of a first architecture, thereby producing a machine program for a computer of a second architecture; a second step of decompiling the machine program, thereby producing a second high-level language source program which does not depend on any architecture; and a third step of compiling and linking the second high-level language source program, thereby producing a first executable load module.