The Disp command displays output in the Home App I/O screen. An example:
prgmexmp() Prgm Request "Enter something",var1 //Get a value for var1 Disp "var1=",var1 Pause DelVar var1 ClrIO DispHome EndPrgm
910 - Syntax happens when there is improper syntax/a variable was not used.
Credits to byobcello for the explanation and code, both were made by him. Modified for readability/corrections