What do the numbers and letters of a dive mean?

• The code: "All dives shall be designated by a system of 3 or 4 numerals followed by a single letter."
• First digit, the group: "1 = Front 2 = Back 3 = Reverse 4 = Inward 5 = Twisting 6 = Armstand".
• Second digit, groups 1 to 4: 1 means the dive has a flying action. Otherwise it is 0.
• Third digit: the number of half somersaults. "1 = ½ somersault, 9 = 4 ½ somersaults".
• Twisting dives: begin with 5. The second digit is the direction of the take-off, the third the half somersaults and the fourth the half twists.
• Armstand dives: begin with 6. The second digit is the direction, and where there is a fourth digit it is the half twists.
• The letter: "A = Straight B = Pike C = Tuck D = Free".
• Free: "any combination of the other positions". Its use is restricted to some twisting dives.
• Examples: 107B is a front dive with three and a half somersaults in the pike position. 5253B is a twisting dive with a back take-off, two and a half somersaults and one and a half twists, in pike.

The glossary has entries for the dive number, the dive groups and the dive positions. A reverse dive faces forward and turns back towards the board. An inward dive faces the board and turns in towards it. A twist turns the body about its long axis.

A diver has to tell the judges in advance exactly what they will do, and a judge has to know at a glance what to expect. A code does that in any language. It also gives every possible dive a place in the difficulty tables, including dives nobody has yet performed.