the like and controls operation by the program in this system at first a source file 1 is translated into a machine language by a compiler 2 to prepare an object file 3 next the object file 3 is linked with a library 6 including an exception handler 5 by a linker 4 to prepare an execution load module 7 the source file 1 is written in a program language capable of processing an exception as instructed by a user within a level of a user program the compiler 2 responds to compiling by the program language next processing procedures taken by the compiler will be explained with reference to fig5 to 9 fig5 is a flowchart showing the processing by the compiler according to the present embodiment the compiler 2 firstly divides a program sequence into base blocks immediately after a branch and at a target of the branch in accordance with normal branch processing to prepare a control flow graph st1 fig6 is a schematic diagram exemplifying a state in which a program sequence is divided into base blocks for example if a block a includes a branch command such as an 34 if 34 sentence subsequent processing can be branched into a plurality of branches in the figure blocks b and c correspond to such branches and the processing is succeeded from the blocks b and c to a block d in this case the blocks a b c and d are divided into base blocks 10a 10b 10c and 10d as shown in fig6 it is to be noted that the base blocks will be referred to.