During play, type in the following codes and press 
Enter to activate:

boxes         Collision boxes around objects    
clearc        Clear caches      
diags         Display diagnostic   
dload         Return to windows 
fly           Flight mode       
getalife      Unlimited lives   
goto          Level skip        
normal        Normal game speed 
pede          Create centipede   
report        Generate report files
robot         Auto firing & movement until player takes control     
showz         Screen modes      
slow          Slower game speed  
sloww         Even slower game speed 
slowww        Even slower than above       
slowwww       Incredibly slow    
times         Time codes        
wimp          God mode