For cheats in this game, use the DOS utility DEBUG. 
 First backup your game to be edited, then type the 
 following from the dos prompt:
                                         
 ren sb.exe sb.cht
 debug sb.cht < sbcht.bat
 For Unlimited ships, type:
 e 550 90 90 90 90
 For Unlimited Smart Bombs, type:
 e d00 90 90 90 90
 For Unlimited Thrust, type:
 e 12a8 90 90 90 90
 e 2824 90 90 90 90
 For Unlimited Ammo, type:
 e 1384 90 90 90 90
 e 2931 90 90 90 90
 For Limited Shield Protection, type:
 e 15c0 0
 e 160f 0
 For Invulnerability, type:
 e 117d 3e
 e 1762 3e
 e 203e 3e
 e 2536 3e
 e 2633 3e
 e 36bb 3e
 w
 q