Electronic device

An electronic device comprising:

• a device body comprising a main system unit and an option unit detachably connected to the main system unit,
• wherein the main system unit comprises:
• a first housing including a first main surface, a second main surface opposing to the first mine surface, a first connection side surface, and a first engagement portion provided at the first connection side surface, and
• a main control circuit board in the first housing, and
• wherein the option unit comprises:
• a second housing including a first main surface continuous with the first main surface of the first housing, a second main surface continuous with the second main surface of the first housing, a second connection side surface configured to oppose to the first connection side surface of the first housing, and the second engagement portion provided at the second connection side surface and configured to detachably engage with the first engagement portion;
• an option device in the second housing;
• a lock mechanism provided at the second housing, and configured to lock the second housing, with the second housing connected to the first housing;
• and
• a release member configured to release from locking of the lock mechanism.