Letter shift codes

The idea

In a Caesar code, every letter moves the same number of places through the alphabet. If the shift is 2 places forward, A becomes C, B becomes D and C becomes E. The alphabet wraps around at the end: Y moves to A and Z moves to B, because after Z we start again at A.

To decode, move each letter the same number of places in the opposite direction. A word coded with a shift of 2 forward is decoded by moving 2 back. Some harder codes alternate, such as moving 1 forward, then 2 forward, then 1, then 2. Compare the first few letters of the given pair to spot the pattern before you start.

Write the letters of the word and the code in neat columns, one above the other. Count each move carefully on an alphabet strip, and check that every letter has moved by the correct amount before you write your answer.

Worked example

Each letter moves 2 places forward in the alphabet. How is CAT coded?

1. C moves 2 forward to E.
2. A moves 2 forward to C.
3. T moves 2 forward to V.

Answer: ECV

Watch out

• Moving letters the wrong way when decoding: decoding reverses the shift.
• Forgetting to wrap around, so Z with a shift of 2 is left stuck instead of becoming B.
• Counting the starting letter as the first move, which makes the shift too small.