MULTITASKING SYSTEM

PROBLEM TO BE SOLVED: To prevent a deadlock between tasks in a multitasking system for using a message to perform inter-task communication. SOLUTION: Each task 10 is provided with a message data storage part 11 having a storage area for storing a data main body of a message for each type of a received message and a message queue 12 having the number of steps as many as the number of types of received messages, overwrites a data main body of a message in a storage area corresponding to the type of the message of the message data storage part 11 in the case of receiving the message, queues information showing that a type of message is received in the message queue 12 in a First In First Out format when the type of the received message has not been queued in the message queue 12 yet, but performs an operation that does not apply any change to the message queue 12 when the type of the received message has already been queued in the message queue 12. COPYRIGHT: (C)2007,JPO&INPIT