A framework is provided which makes it possible to appropriately determine the printing starting timing, and to start printing, without waiting for the compression processing in the host device to be completed. A host based printer receives compressed data of a print image from the host device, restores the print image by expanding this compressed data, and executes printing on the basis of the print image. This host based printer comprises means for storing the timing S at which it is determined whether or not a printing operation can be started, means for predicting the data quantity q of the residual compressed data of the print image on the basis of the data quantity p of the compressed data that has been received by the timing S for the print image when this timing S arrives, means for predicting the time T1 that is required to receive the data of this data quantity q, means for predicting the time T2 that is required to print the print image, and means for causing a printing operation that restores the print image and executes printing to take place in cases where T1 is equal to or less than T2.