A digital copier has a memory for storage of image data, reads image data and stores the image data in the memory, and prints an image depending on the image data stored in the memory. The digital copier can also register a plurality of jobs. Based on a registered job an image is printed. Then, based on the subsequent job an image is printed. When an image data corresponding to a new job cannot be stored in the memory, the digital copier effects the process for calculation of job execution time, a process of calculating a free memory capacity, and a process of calculating the time required for obtaining a timing at which a free memory space is provided, to display the time at which the image data corresponding to the new job can be stored. Thus, a digital copier can be provided allowing the user to form images efficiently.