component described with reference to fig5 and 3 as shown in fig1 the microcomputer 38b includes a rom 45b for storing the receiving program it results in reducing the storage area of the rom 36 included in each of the common cassettes 23 as shown in fig3 that is as shown in fig1 the necessary area is only the ram 37 for storing the game program fig1 is a block diagram showing an internal of a third embodiment of each of the child game machines shown in fig1 8 and 9 each of the components shown in fig1 with the same numerals as ones shown in fig5 means the same as the component described with reference to fig5 fig1 is a block diagram showing an internal of a third embodiment of one of common cassettes for a multi player game shown in fig1 8 and 9 each of the components shown in fig1 with the same numerals as ones shown in fig3 means the same as the component described with reference to fig3 further as shown in fig1 and 15 in case that the microcomputer 38b of the child game machine 24 has a ram 46b for storing the game program it results in reducing the storage area of the ram 37 included in each of the common cassettes 23 shown in fig3 that is as shown in fig1 the.