There are a number of predefined variables provided ISPP:
| __COUNTER__ | int. Automatically increments each time it is used (afterwards). |
| __FILENAME__ | str. Similar to __PATHFILENAME__, but returns only the filename portion. |
| __INCLUDE__ | str. Returns the current include path (or paths delimited with semicolons) set via #pragma include. |
| __LINE__ | int. Returns the number of the line in the current file. |
| __OPT_X__ | void. Defined if specified option set via #pragma option -x+ is in effect. In place of "X" may be any letter from "A" to "Z." Use Defined function to test whether the variable is defined. |
| __DIR__ | str. Similar to __PATHFILENAME__, but returns only the directory portion, excluding a trailing backslash (unless it is a root directory). |
| __PATHFILENAME__ | str. Returns the full path of the current include file. Empty string for the root script file. |
| __POPT_X__ | void. Defined if specified parser option set via #pragma parseroption -x+ is in effect. In place of "X" may be any letter from "A" to "Z." Use Defined function to test whether the variable is defined. |
| __WIN32__ | void. Always defined. |
| ISPP_INVOKED | void. Always defined. |
| ISCC_INVOKED | void. Defined if compilation was invoked using the console-mode compiler, ISCC.exe. |
| PREPROCVER | int. Returns the 32-bit encoded version of ISPP. Highest byte holds the major version, lowest byte holds the build number. |
| WINDOWS | void. Always defined. |
| UNICODE | void. Always defined. |
| CompilerPath | str. Points to the directory where the compiler is located. |
| SourcePath | str. Points to the directory where the root script file is located, or the My Documents directory if the script has not yet been saved. |
| Ver | int. Returns the 32-bit encoded version of Inno Setup compiler. Highest byte holds the major version, lowest byte the minor version. |
| NewLine | str. Returns the newline character. Declared in ISPPBuiltins.iss. |
| Tab | str. Returns the tab character. Declared in ISPPBuiltins.iss. |