1. A computer-readable storage medium storing a generational garbage collection program used to direct a computer to perform a generational garbage collection process, the generational garbage collection process comprising: a generational garbage collection environment preparing and initializing process; and a full garbage collection process, wherein the generational garbage collection environment preparing and initializing process comprises: a process of allocating a single virtual memory space as a virtual memory space of all generations, and distributing the single virtual memory space to each generation such that the virtual memory space of each generation can be continuously arranged in order of generation in the single virtual memory space; and a process of committing memory to the single virtual memory space such that, when there are contiguous spaces to which memory is committed, and there is a space to which the memory is not committed in the single virtual memory space, the space to which the memory is not committed can be provided in a newest generation, the full garbage collection process comprises: filling a space with dead objects when there is the space where no object exists between generations in a space to which memory is committed in the single virtual memory space; releasing a boundary between generations in the single virtual memory space; performing a garbage collection process in a space to which memory is committed in the single virtual memory space; and redistributing the single virtual memory space to each generation such that a virtual memory space of each generation can be contiguously arranged in order of generation in the single virtual memory space.