Structure for modular computer

PURPOSE: A modularity computer structure is provided to maximize a life cycle of a computer system by changing a module easily and interfacing modules. CONSTITUTION: An interface module(101) includes a control signal line, a bus line, a PCB formed according to a rear structure of a housing, and many connectors being connected on the PCB. The connectors comprise a connector for connecting to a CPU module(115), a connector for connecting to a rear port module(103), and many slots for connecting to an ODD(Optical Disk Drive) module(109) and an HDD module(111). The rear port module(103) includes a port for connecting to a plurality of input/output devices. A power supply module(105) includes a connector for supplying a power to the interface module(101), supplies an electric power supply state to the CPU module(115) through the interface module(101), and displays an operation state of a power supply through a display element. In the case that an I/O expansion module(117) is not used by a user, a spare module(107) adds the ODD module(109) and an HDD module(111). The spare module(107) includes a connector which is capable of connecting to the ODD module(109) and an HDD module(111).