Editing Aztec Code (section)

=== Character set ===
All 8-bit values can be encoded, plus two escape codes:
* FNC1, an escape symbol used to mark the presence of an application identifier, in the same way as in the [[GS1-128]] standard.
* ECI, an escape followed by a 6-digit [[Extended Channel Interpretation]] code, which specifies the character set used to interpret the following bytes.

By default, codes 0–127 are interpreted according to ANSI X3.4 ([[ASCII]]), and 128–255 are interpreted according to [[ISO/IEC 8859-1]]: Latin Alphabet No. 1.  This corresponds to ECI 000003.

Bytes are translated into 4- and 5-bit codes, based on a current decoding mode, with shift and latch codes for changing modes.  Byte values not available this way may be encoded using a general "binary shift" code, which is followed by a length and a number of 8-bit codes.

For changing modes, a ''shift'' affects only the interpretation of the single following code, while a ''latch'' affects all following codes.  Most modes use 5-bit codes, but Digit mode uses 4-bit codes.

{|class="wikitable" style="text-align:center"
|+ Aztec code character encoding
!rowspan=2 scope="col"| Code ||colspan=5 scope="col"| Mode
|rowspan=18|
!rowspan=2 scope="col"| Code ||colspan=4 scope="col"| Mode
|-
!scope="col"| Upper ||scope="col"| Lower ||scope="col"| Mixed ||scope="col"| Punct ||scope="col"| Digit
!scope="col"| Upper ||scope="col"| Lower ||scope="col"| Mixed ||scope="col"| Punct
|-
!scope="row"| 0
| P/S || P/S || P/S || FLG(''n'') || P/S
!scope="row"| 16
| O || o || ^\ || +
|-
!scope="row"| 1
| SP || SP || SP || CR || SP
!scope="row"| 17
| P || p || ^] ||, 
|-
!scope="row"| 2
| A || a || ^A || CR LF || 0
!scope="row"| 18
| Q || q || ^^ || -
|-
!scope="row"| 3
| B || b || ^B || . SP || 1
!scope="row"|  19
| R || r || ^_ || .
|-
!scope="row"| 4
| C || c || ^C ||, SP || 2
!scope="row"| 20
| S || s || @ || /
|-
!scope="row"| 5
| D || d || ^D || : SP || 3
!scope="row"| 21
| T || t || \ || :
|-
!scope="row"| 6
| E || e || ^E || ! || 4
!scope="row"| 22
| U || u || ^ || ;
|-
!scope="row"| 7
| F || f || ^F || " || 5
!scope="row"| 23
| V || v || _ || <
|-
!scope="row"| 8
| G || g || ^G || # || 6
!scope="row"| 24
| W || w || ` || =
|-
!scope="row"| 9
| H || h || ^H || $ || 7
!scope="row"| 25
| X || x || {{pipe}} || >
|-
!scope="row"| 10
| I || i || ^I || % || 8
!scope="row"| 26
| Y || y || ~ || ?
|-
!scope="row"| 11
| J || j || ^J || & || 9
!scope="row"| 27
| Z || z || ^? || [
|-
!scope="row"| 12
| K || k || ^K || ' ||, 
!scope="row"| 28
| L/L || U/S || L/L || ]
|-
!scope="row"| 13
| L || l || ^L || ( || .
!scope="row"| 29
| M/L || M/L || U/L || {
|-
!scope="row"| 14
| M || m || ^M || ) || U/L
!scope="row"| 30
| D/L || D/L || P/L || }
|-
!scope="row"| 15
| N || n || ^[ || * || U/S
!scope="row"| 31
| B/S || B/S || B/S || U/L
|}
* Initial mode is "Upper"
* x/S = Shift to mode x for one character; B/S = shift to 8-bit binary
* x/L = Latch to mode x for following characters
* Punct codes 2–5 encode two bytes each
* The table lists ASCII characters, but it is the byte values that are encoded, even if a non-ASCII character set is in use

B/S (binary shift) is followed by a 5-bit length.  If non-zero, this indicates that 1–31 8-bit bytes follow.  If zero, 11 additional length bits encode the number of following bytes less 31.  (Note that for 32–62 bytes, two 5-bit byte shift sequences are more compact than one 11-bit.)  At the end of the binary sequence, the previous mode is resumed.

FLG(''n'') is followed by a 3-bit ''n'' value.  ''n''=0 encodes FNC1.  ''n''=1–6 is followed by 1–6 digits (in digit mode) which are zero-padded to make a 6-bit ECI identifier.  ''n''=7 is reserved and currently illegal.