Back in the days of 35mm film, a 50mm prime was considered a 'standard' lens. That's because it gives pretty much the same perspective as viewing a scene with the human eye, without the magnification of a telephoto lens or the shrinkage a wide-angle lens uses to squeeze more into the frame.
The flexi disc (also known as a phonosheet or Soundsheet, a trademark) is a phonograph record made of a thin, flexible vinyl sheet with a molded-in spiral stylus groove, and is designed to be playable on a normal phonograph turntable.
USB flash drives have become an easier way to store and transfer data than burning CDs and DVDs. USB flash drives are nearly infinitely re-writable, whereas most DVDs can only be written to a few times. The flash drives are also easier to carry around, without worry of scratching. In order to transfer the contents of the DVD to a USB flash drive, you can simply copy and paste between the two.