Program ratings have different effects. OPERATIONAL UTILITIES like Analyze etc. reduce the target number for system tests. So if you're editing a file the Read/Write utility reduces the target number for Edit File tests, etc. So if I'm editting portfolios that are in an accounting host I need to roll my Decking test + Hacking Pool against the FILES rating of the Host in question. My target number is reduced by the highest rated Read/Write utility in ACTIVE memory on my deck. Likewise, the system makes a test against my Detection Factor ((Masking + Active Sleaze)/2) using its Security rating, this is the number next to the host color, ie. Red 11, Blue 4, Orange 8, etc. If the system scores more successes, my action fails. If I score more successes, the file action succeeds and reduces the time needed to edit the file.
Direct Combat utilities (Attack, Killjoy, and Black Hammer) are treated like Real-life weapons, with two ratings the Attack Power (This is the utility's actual rating) and the Damage Level. Higher damage level programs have a greater size multiplier. So a rating 10 Light Attack program will be much smaller than a rating 7 Deadly Attack Program. The attack power is treated just like a bullet, knife etc. The program's rating is used for the target number to resist the damage. The target when hit, uses it's Bod (or Security rating) to resist the damage, rolling those dice + pool dice against a target number equal to the Attack utility rating or IC rating minus the rating of any active Armor utility.
Other programs have their rating used based on their description. So, if you want to know more about them, you'll just have to read how they work, chummer.
