Before DigiTcl can be used, the appropriate shell variables must be set and exported to the environment. Some of these environment variables may be required by the underlying graphics toolkit, Tcl/Tk (see Table A.2), while others are required by DigiTcl, itself (see Table A.3). The standard PATH environment variable may also be modified for user convenience.
| Environment | Description |
| Variable | |
| TCL_LIBRARY | Set to the location of the Tcl library files. It is not necessary to set this environment variable if tclsh was compiled with the library path pre-configured in its binary. |
| TK_LIBRARY | Set to the location of the Tk library files. Again, it is not necessary to set this environment variable if wish was compiled with the library path pre-configured in its binary. |
| Environment | Description |
| Variable | |
| DIGISIM | Set to the location of the simulator engine compiled earlier. An absolute pathname should be used. |
| DIGILIB | Set to the location of auxiliary bitmap and cursor files required by the circuit editor. Again, an absolute pathname should be used. |
| DIGIUSER | Set to the location of the working directory to be used by digitcl. When loading or saving circuits, the contents of the directory indicated by this environment variable will be presented in the file selection dialog box. |
| PATH | This standard environment variable should include the location of the wish binary. It may also contain the location of the digitcl script. |