Abstract: An image forming apparatus capable of processing data at a relatively high speed in accordance with a data transmission speed from a host system. The image forming apparatus includes a central processing unit, a memory, and a host system interface. When data inclusive of print data and control data is transmitted from the host system to the image forming apparatus, the host system interface starts a direct memory access (DMA) with the memory to store the print data at a relatively high speed in accordance with the data transmission speed from the host system. The host system interface includes a data receiver to be connected to the host system, a data determiner, a control data checker, a print data register, a control data register, a DMA address register, and an address counter.