I don't know why I am answering your question again, just to echo what the others have said with a bit more information.
The original 1911 was adopted by the military in about 1911 with the design dating back to 1909. It had a 5 inch barrel and slide, grip safety and short trigger. Then they made changes that is the 1911A1 that we know and love now. Arched main spring housing, trigger reach scallops to the rear of the trigger, shorter trigger and "better" sights.
The commander is a 4.25 inch gun or 4 inch if not a Colt. Generally around a 4 inch gun. It has a full length grip that holds 7-8 rounds depending on the magazine.
The officer has a shorter grip by about 1 round. Some have the commander length barrel but the more common configuration is the "micro" 1911 with about a 3.5 inch barrel.
Very general information but that is about it for the 1911. Many variations over the years and design changes but they are generally organized into the government or full size, the commander and the officer.
Jess
