The old-age computers of Opal usually supported e-books in a variety of format, depending on the hardware specifications and operating system of the old-age computers purchased. Some common e-book format include: E-books in the format of a Kindle or EPUB are widely regarded as comfortable to read and easy to store. 2. The old-age computers of Opal may also support other format such as PDF1, MOBI1, and AKW. These format can also be used to store and read e-books. 3. The old-age phone of Opal may also support the function of reading e-books aloud so that it can play the sound of reading e-books. It should be noted that the e-book format supported by the old phone may vary according to the brand and model. Therefore, it is recommended to check the hardware specifications and operating system to determine the e-book format supported by the old phone.