Answers.Body: <p>The castling notation was invented by Johann Allgaier and used for the first time in his 1811 2nd edition of his <em>Neue theoretisch-praktische Anweisung zum Schachspiel</em>.</p>
  
  <p>He didn't explain why he came up with it.</p>
  
  <p>Allgaier (and algebraic notation in general) used digit-0. The use of letter-O is an anglo-saxon oddity.</p>
  
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Answers.Text: I always thought of the kingside notation as being a couple of circles with a line between, representing the bottoms of the king and rook, and the queenside notation was a "bigger" version of that.  I've never thought there was any relation to the number zero.
Answers.UserDisplayName: supercat
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Answers.Text: @supercat  there is no relation to the number zero  it is the letter 'oh' and pronounced oh-oh  or oh-oh-oh  never zero-zero or zerozerozero like the movie title.
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Answers.Text: @edwinaoliver I don't think so. For instance, Spanish uses 0-0-0 ("cero-cero-cero")
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Answers.UserDisplayName: Queeg
Answers.Body: <p>A notation like Kg1 would give the impression that only the king is moved. At the very least, it is not <em>obvious</em> that castling moves the rook as well.</p>
  
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Answers.UserDisplayName: Glorfindel
Answers.Body: <p>The point is to make it obvious it's a castling move. It's important because that's the only time in a game that you can move two pieces.</p>
  
  <p>Note that computers represent the moves as Kc1 and Kg1, so both ways work. O-O and O-O-O are easier for humans to read.</p>
  
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Answers.UserDisplayName: SmallChess
Answers.Body: <p>In my opinion, 0-0 and 0-0-0 are used to differentiate castling from ordinary king moves. The castling maneuver then stands out in the game notation, as opposed to say Kc8 which appears - on the surface anyway - to be an ordinary, one square, king move ... until you look closer to see if the king is actually moving more than one square. It also helps to clearly indicate king-side (short) or queen-side (long) castling at a glance.</p>
  <p>I think at least as compared to things like ?! or !? it makes a lot of sense.</p>
  <p>Oddly, it's the only carry-over from the Descriptive (P-K4) to Algebraic (e4) notation.</p>
  
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Answers.UserDisplayName: Joe Quimby
Answers.Body: <p>Kg1/Kg8 or Kc1/Kc8 are Singular moves where the King only moves during the Game . Since before the Algebraic Notation Descriptive Notation was used which was quite cumbersome &amp; lengthy Algebraic was a short hand . Why 0-0 &amp; 0-0-0 was exactly used is quite inexplicable but this is the only move in International Chess where two pieces are moving simultaneously . In K-side Castling K is moving two squares and in Q-side Castling it is moving three Squares . </p>
  
  <p>So it might have seen an innovative way of recording the Castling move since King is the most important piece in a Chess Game 0-0/0-0-0 was a royal move indicating King is going inside the castle and the Battle Begins . </p>
  
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2017-09-15T12:36:12.243Z
Answers.Text: If the K moved three squares in Q-side castling it would end up on b1.
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Answers.UserDisplayName: Seth Projnabrata
Body: <p>I'm curious about why the symbols O-O and O-O-O are used for castling in algebraic notation.</p>
  <p>Why not use the consistent and logical Kg1/Kc1 for White and Kg8/Kc8 for Black? Why adopt the less-than-obvious O-O and O-O-O from descriptive notation?</p>
  
Comments.ContentLicense: CC BY-SA 3.0
Comments.CreationDate: 2017-03-10T19:44:57.250Z
Comments.Text: 0-0 and 0-0-0 are more "obvious" if you realize it's the number of squares the rook moves.  (Comment, because it's really not a full answer.)
Comments.UserDisplayName: Ghotir
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Comments.CreationDate: 2017-03-10T21:30:26.753Z
Comments.Text: BTW, it should be 0-0 (with the number zero, not the letter O). Only in PGN it has to be the letter.
Comments.UserDisplayName: user1583209
Comments.ContentLicense: CC BY-SA 3.0
Comments.CreationDate: 2017-03-10T21:33:02.073Z
Comments.Text: According to wikipedia this notation was introduced in 1811 by Johann Allgaier as 0-0r, 0-0l. The current notation with 0-0-0 was added in 1837 by Aaron Alexandre.
Comments.UserDisplayName: user1583209
Comments.ContentLicense: CC BY-SA 3.0
Comments.CreationDate: 2017-09-15T09:45:44.100Z
Comments.Text: Better would be CQ and CK, instead of Kc1 and Kg1.
Comments.UserDisplayName: Fred Knight
Tags: <history><castling><notation>
Title: Why are the symbols O-O and O-O-O used for castling in algebraic notation?
ThreadText: # Why are the symbols O-O and O-O-O used for castling in algebraic notation?
  
  (Asked by: username_0 on 2017-03-10)
  
  I'm curious about why the symbols O-O and O-O-O are used for castling in algebraic notation.
  
  Why not use the consistent and logical Kg1/Kc1 for White and Kg8/Kc8 for Black? Why adopt the less-than-obvious O-O and O-O-O from descriptive notation?
  
  **Tags:** history, castling, notation
  
  > **Comments:**
  > **username_1**: 0-0 and 0-0-0 are more "obvious" if you realize it's the number of squares the rook moves.  (Comment, because it's really not a full answer.)  
  > **username_2**: BTW, it should be 0-0 (with the number zero, not the letter O). Only in PGN it has to be the letter.  
  > **username_2**: According to wikipedia this notation was introduced in 1811 by Johann Allgaier as 0-0r, 0-0l. The current notation with 0-0-0 was added in 1837 by Aaron Alexandre.  
  > **username_3**: Better would be CQ and CK, instead of Kc1 and Kg1.  
  
  ---
  
  ## 5 answers
  
  ### Answer by username_4 on 2017-03-10. Score: 16
  
  The castling notation was invented by Johann Allgaier and used for the first time in his 1811 2nd edition of his *Neue theoretisch-praktische Anweisung zum Schachspiel*.
  
  He didn't explain why he came up with it.
  
  Allgaier (and algebraic notation in general) used digit-0. The use of letter-O is an anglo-saxon oddity.
  
  > **Comments:**
  > **username_5**: I always thought of the kingside notation as being a couple of circles with a line between, representing the bottoms of the king and rook, and the queenside notation was a "bigger" version of that.  I've never thought there was any relation to the number zero.  
  > **username_6**: @username_5  there is no relation to the number zero  it is the letter 'oh' and pronounced oh-oh  or oh-oh-oh  never zero-zero or zerozerozero like the movie title.  
  > **username_7**: @username_6 I don't think so. For instance, Spanish uses 0-0-0 ("cero-cero-cero")  
  
  ---
  
  ### Answer by username_8 on 2017-03-10. Score: 8
  
  A notation like Kg1 would give the impression that only the king is moved. At the very least, it is not *obvious* that castling moves the rook as well.
  
  
  ---
  
  ### Answer by username_9 on 2017-03-10. Score: 5
  
  The point is to make it obvious it's a castling move. It's important because that's the only time in a game that you can move two pieces.
  
  Note that computers represent the moves as Kc1 and Kg1, so both ways work. O-O and O-O-O are easier for humans to read.
  
  
  ---
  
  ### Answer by username_10 on 2017-09-20. Score: 1
  
  In my opinion, 0-0 and 0-0-0 are used to differentiate castling from ordinary king moves. The castling maneuver then stands out in the game notation, as opposed to say Kc8 which appears - on the surface anyway - to be an ordinary, one square, king move ... until you look closer to see if the king is actually moving more than one square. It also helps to clearly indicate king-side (short) or queen-side (long) castling at a glance.
  
  I think at least as compared to things like ?! or !? it makes a lot of sense.
  
  Oddly, it's the only carry-over from the Descriptive (P-K4) to Algebraic (e4) notation.
  
  
  ---
  
  ### Answer by username_11 on 2017-03-11. Score: -1
  
  Kg1/Kg8 or Kc1/Kc8 are Singular moves where the King only moves during the Game . Since before the Algebraic Notation Descriptive Notation was used which was quite cumbersome & lengthy Algebraic was a short hand . Why 0-0 & 0-0-0 was exactly used is quite inexplicable but this is the only move in International Chess where two pieces are moving simultaneously . In K-side Castling K is moving two squares and in Q-side Castling it is moving three Squares .
  
  So it might have seen an innovative way of recording the Castling move since King is the most important piece in a Chess Game 0-0/0-0-0 was a royal move indicating King is going inside the castle and the Battle Begins .
  
  > **Comments:**
  > **username_12**: If the K moved three squares in Q-side castling it would end up on b1.  
  
  ---
  
  