Letter Shift Coding

In letter shift coding, every letter in a word is replaced by a letter that is a fixed number of steps forward or backward in the alphabet. For example, with a +2 shift: A becomes C, B becomes D, C becomes E, and so on. To decode, you reverse the shift. Knowing the alphabet positions (A=1, B=2, C=3 … Z=26) is essential. Shifts also wrap around: with +2, Y becomes A and Z becomes B.

1. Write the alphabet in a row with positions: A=1, B=2 … Z=26.
2. Find the shift value by comparing one known letter in the code to the original: if M is coded as P, then P(16) - M(13) = +3 shift.
3. Apply that shift to every letter of the word you need to encode or decode.
4. For decoding, subtract the shift instead of adding.
5. Handle wrap-around: if a shift takes you past Z (26), continue from A.

Example 1 (encode, +3 shift): Code the word CAT.

• C(3) + 3 = F(6)
• A(1) + 3 = D(4)
• T(20) + 3 = W(23)
• Coded word: FDW.

Example 2 (decode, +2 shift): The coded word is EQQNG. Decode it.

• E(5) - 2 = C(3)
• Q(17) - 2 = O(15)
• Q(17) - 2 = O(15)
• N(14) - 2 = L(12)
• G(7) - 2 = E(5)
• Decoded word: COOLE → COOL E — actually COOLE means the word is COOLE. Checking: the decoded answer is COOLE, so the original is COOLE (here it decodes to the word COOLE).

• Forgetting wrap-around: Z + 1 = A (not a symbol or nothing).
• Using the wrong direction: if the rule is +2, decoding requires -2, not another +2.
• Misreading a letter — O and Q look similar; I and L look similar in print. Check carefully.

1. With a +4 shift, encode the word SUN.
2. A word is coded as HEJ with a +3 shift. What is the original word?