EMULATION SYSTEM

PURPOSE:To obtain emulation in a less number of steps, by discriminating an input-output controlling macro instruction from the user program of a target machine by means of an SVC instruction and providing a function which distributes interrupting processes in the native mode in an SVC jump table. CONSTITUTION:When the user program 16 of the target machine is detected or an SVC instruction is detected in an operating system 15, a previously prepared SVC jump table is retrieved on the basis of the operand of the instruction. If the instruction is the SVC instruction by an input-output controlling macro instruction, the condition which executes the instruction of the target machine is once released and software (ECP) 13 which controls emulation is caused to issue an interruption. At the ECP 13 an input-output macro instruction process is performed by replacing the value retrieved from the SVC jump table with the operand section of the SVC instruction of the native mode and executing the SVC instruction of the native mode.