Table of TeX category codes
| Category code | Description | Standard LATEX/TEX |
|---|---|---|
| 0 | Escape character—tells TEX to start looking for a command | \ |
| 1 | Start a group | { |
| 2 | End a group | } |
| 3 | Math shift—switch in/out of math mode | $ |
| 4 | Alignment tab | & |
| 5 | End of line | ASCII code 13 (\r) |
| 6 | Macro parameter | # |
| 7 | Superscript—for typesetting math: $y=x^2$ \(y=x^2\) | ˆ |
| 8 | Subscript—for typesetting math: $y=x_2$ \(y=x_2\) | _ |
| 9 | Ignored character | ASCII 0 <null> |
| 10 | Spacer | ASCII codes 32 (space) and 9 (tab character) |
| 11 | Letter | A...Z, a...z, (and thousands of Unicode characters) |
| 12 | Other | 0...9 plus ,.;?" and many others |
| 13 | Active character | Special category code for creating single-character macros such as ˜ |
| 14 | Comment character—ignore everything that follows until the end of the line | % |
| 15 | Invalid character, not allowed to appear in the .tex input file | ASCII code 127 (DEL) |