You can send lines of G-Code into your Pronterface UI to give manual commands to your Printrbot. These codes can also be inserted into existing G-Code to adjust behavior during the print.
For instance, if you wanted the fan to turn on before the hot end began to go to temp, you would insert the following code to the beginning of your text file.
M106 (fan on)
M104 S210 (set extruder temperature to 210C)
Click here for a full list from reprap.org.
Below, are some of the most commonly used g-code commands.
|G28 X0 Y0 Z0||Home all axes|
|G29||Probe the print bed|