ESP8266 - Sending a software Reset Command
1/0 is an exception (divide by zero). esp8266 arduino core has soft reset: ESP.reset(). Calling this function you get a valid reset.

Note to software reset. esp8266 has a bug. If software reset (or exception) is executed in program started right after the flashing, the board goes back to flashing mode because the flashing flag is still active. Perhaps you noticed that after flashing the bootloader doesn't reset the board, but executes the flashed code.