ICS signal flags quiz

The International Code of Signals (ICS / ICOS) uses 26 alphabet flags (A–Z), 10 numeral pendants, and 4 substitute flags. Single-letter signals have specific urgent or important meanings under the ICS — for example, Flag O means man overboard and Flag Q means the vessel is requesting free pratique.

Two quiz modes: identify the letter for a given flag, or identify the single-letter meaning. Use this for STCW oral-exam revision or watchkeeping refresher.

See also

• · ICS flags reference — full alphabet flag chart with meanings.
• · Morse code — flashing light and sound signalling.
• · GMDSS — Global Maritime Distress and Safety System channels and procedures.

Last updated 2026-04-27