a person who designs and writes and tests computer programs
"The new coder spent all night debugging the error in our payment system so customers could check out again."
A device that generates a code, often as a series of pulses.
"The old typewriter had a built-in coder that sent Morse code pulses to signal an incoming message."
A surname.
"At the family reunion, everyone was surprised to learn that our distant cousin's last name is actually Coder."