When a control program is executed, it needs to be first decompressed and loaded into RAM. It has been impossible to immediately execute the control program when it is requested, causing a hindrance to processing speed acceleration. A printing apparatus is mounted with volatile memory that provides a main storage area. The printing apparatus specifies a second control program to be preferentially decompressed on the basis of a storage capacity of the volatile memory. The printing apparatus decompresses the specified second control program before execution and loads it into the volatile memory. Accordingly, there is no need for decompression and the like during execution of the second control program. It is possible to increase processing speeds of the first and second control programs.

There are provided an image coding method and apparatus and image compression method and apparatus which can properly compress a color document image with a high compression efficiency. First of all, a color reduction processing unit (102) converts each pixel of a color document image into an index assigned in correspondence with a color value, and generates color information (103) containing the number of pixels for each indexed color and an index color image (104). A color information sort unit (105) and the like determine, for example, a color value corresponding to an index of the maximum number of pixels as a background color. An order determination unit (113) determines an order. A binary image generation compression unit (109) generates a partial binary image for each index and compresses the binary image according to the order. A data integrating unit (111) generates compressed image (112) by integrating background data (108) and the compressed data of the partial binary image.