Coding–Decoding
Coding–decoding gives you a made-up rule and asks you to apply it. There is no knowledge to recall — only a method. The single most useful preparation is knowing the letter positions A=1 … Z=26 cold, because most codes are built on shifting, reversing or numbering letters.
Don't read this page — work through it. Each block asks you to commit to an answer before it tells you anything.
Start here: what do you already know?
Coding–decoding — true or false?
6 statements · 10s each
The one table you must know
Letter positions are the backbone of the whole chapter. The EJOTY trick helps: E=5, J=10, O=15, T=20, Y=25 — five landmarks, five apart. Any letter is then a short count from the nearest landmark.
| A | B | C | D | E | F | G | H | I | J | K | L | M |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 |
| N | O | P | Q | R | S | T | U | V | W | X | Y | Z |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 |
Fix the landmarks
Classify the code before you crack it
Deciding which kind of code you are looking at is most of the battle.
Method, in order
Pair the code to its rule
Quick reference
Exam tip: always test the shift in both directions. Candidates lose marks by spotting +1 on the first letter and never checking that the third letter actually moved −1.