1. An information processing system that processes tasks generated based on events transmitted from one or more peripheral devices after storing the tasks into a buffer, comprising: a unit that generates tasks; and a device having the buffer, the device processes the tasks, wherein the unit: sets event largest possible values used for limitation of the number of the tasks and/or the size of areas in the buffer; generates a task without reaching any of the event largest possible values when an event is received from any of the one or more peripheral devices, and reserves an area in the buffer for the task; determines whether or not another new event has been received from any of the one or more peripheral devices before process of the task is completed; deletes the task and releases the area in the buffer for the task upon completion of the process of the task if another new event has not been received; if another new event has been received and both the number of the tasks and the size of areas in the buffer for the tasks do not reach the event largest possible values, generates a new task and reserves an area in the buffer for the new task; and if another new event has been received and either the number of the tasks or the size of areas in the buffer for the tasks reaches any of the event largest possible values, reuses the task and the area for the task in the buffer for the new event after process of the task is completed and wherein the peripheral device is a personal computer, the device that processes the tasks is an image forming device, and the unit is a print server connecting the personal computer and the image forming device.