1 What is this?
Basically, a way to express and write down movements in a chess game, specifically, chess games played over regular (analog) correspondence.
2 Why is it needed?
Generally, because Algebraic Notation can cause some misunderstandings between players speaking different languages. In general, Algebraic Notation uses the initial letter of each piece and the destination square to denote a movement. The problem with this is that different languages have different names for the pieces (who knew?).
So in order to avoid confusion between players who might have different languages and notations^{1} the International Correspondence Chess Federation (ICCF) uses a purely numerical notation, using what might be a more universal system among different nations: Arabic numerals.
3 How does it work?
Simply put:
 Assign a unique number to each square;
 For every move, concatenate the numbers of the start and end squares to obtain a fourdigit number;
 If the move results in a promotion, add a single digit to denote which piece a pawn is being promoted to;
 ???
 Profit!
The chessboard is numbered in the following way:
 Files (as seen from White’s perspective) will indicate the first digit of each square, so that A=1, B=2, etc.
 Ranks (as seen from White’s perspective) will indicate the second digit of each square, so that the closes rank to White is 1, the second closest is 2, etc.
8 
18 
28 
38 
48 
58 
68 
78 
88 
7 
17 
27 
37 
47 
57 
67 
77 
87 
6 
16 
26 
36 
46 
56 
66 
76 
86 
5 
15 
25 
35 
45 
55 
65 
75 
85 
4 
14 
24 
34 
44 
54 
64 
74 
84 
3 
13 
23 
33 
43 
53 
63 
73 
83 
2 
12 
22 
32 
42 
52 
62 
72 
82 
1 
11 
21 
31 
41 
51 
61 
71 
81 
Rank/File 
A 
B 
C 
D 
E 
F 
G 
H 
As one can see, the board is numbered so that all squares have a unique number attached to them.
A move is recorded by taking the “origin” square’s number and concatenating it with the “destination” square. For instance, the opening move usually denoted by e4
in algebraic Notation is recorded as 5254
in Numeric Notation.
Some things to note:
 In this notation, captures are not recorded.
 In this notation, promotion is recorded by adding a single digit at the end of the move:
1
for Queen;
2
for Rook;
3
for Bishop; and
4
for Knight
 Castling is recorded by noting the King’s movement, so that Queenside castling for White is
5131
and Kingside castling is 5171
. For black, these moves are recorded as 5838
for Queenside and 5878
for Kingside castling.
4 Isn’t this rendered moot in the Information Age?
No it’s not… in a way. The ICCF’s Laws of Correspondence Chess establishes Algebraic Notation as their standard for server games and Numeric Notation for nonserver games.^{2}
From a purely theoretical point of view, it’s wonderful to capture Chess in something as simple as a series of four (five) digit numbers. I love it because it encodes the simplest, most mechanical part of chess so that highlevel analysis can be done in other ways.
But of course, as technology has advanced, the ambiguity behind Algebraic Notation has disappeared almost completely (partly because English is now the lingua franca of the Internet, partly because it’s relatively trivial to “translate” between languages with a computer) and nowadays it’s simpler to actually move a piece in a virtual–and sometimes physical—chessboard and let a computer do the actual record of the movement in whatever form they may desire.
The simplicity of Numeric Notation plays against it for actual analysis… Granted, some people can play blind chess, but for the rest of us it’s useful to have a more verbose notation to aid in human analysis of chess. Given that PGN was made to be Machine and Humanreadable, it’s no surprise to see it as the lingua franca of most chess that has to go through a computer, be it modern Chess books, games over the internet and even most Machine Learning engines.
5 Relevant links
6 See also
 PGN—Portable Game Notation, a textbased standard for computers and humans;
 FEN—ForsytheEdwards Notation, a textbased standard for static chess positions, useful in Fischer random chess, also known as Chess960

And confusion when two identical pieces can move to the same end square.

According to the ICCF’s Laws: “nonserver: 6.9 forms of correspondence chess that use move transmission other than through the ICCF server. These typically include postal, email, and far more rarely fax transmissions of moves.”
🜞—
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