I was wondering how does ATC keep track of where a plane under IFR is going i.e. fixes, airways, etc. if all the plane is is a dot with speed and altitude on it. I can't see how the controller knows how to keep track of an airplane he has given vectors to if there are 40-50 others in his sector at the same time.
This is a DSR data block. DSR is used by enroute centers (Air Route Traffic Control Center). You can see the callsign, the altitude to which the aircraft has been cleared, an up arrow indicating the aircraft is currently climbing, the current altitude, a computer generated ID code (779) and the current ground speed (250). The "blip" is the diamond on the left side of the picture, with the vector line indicating the aircraft is on a southeasterly heading. The /V next to the callsign is not seen on real world scopes, as this picture is taken from the documentation of an online ATC system known as VATSIM and indicates whether or not the pilot flying the aircraft is able to transmit on a voice frequency. If not voice, text is used.
An ARTS (Automated Radar Terminal System) data block is seen in the departure and approach facilities (TRACON) and displays similar data, but lacks information on what altitude to which the aircraft has been cleared as well as the computer code. It is only two lines instead of three, with the current altitude and ground speed being combined on the second line.
The host computer (mainframe for all ATC facilities) receives a flight plan from flight service and generates a computer ID and squawk code for that flight. The pilot calls clearance delivery and receives his route clearance and squawk code and then inputs that squawk code into his transponder. When the ATC radar system receives the squawk code reply from the transponder, it matches up that squawk code to the flight plan in the system and associates the two and displays the appropriate callsign on the controllers scope.
In addition to squawk codes, the host computer distributes a flight strip to each appropriate control facility along the route of flight. When it is printed off at the departure airport, a "strip runner" puts it in a strip holder and places it at the workstation of the first controller that the aircraft will talk to after departure. As the aircraft progresses on its flight, the strip is handed down the line of controllers at that specific facility. It could be just the one departure controller (if it is a relatively slow facility) or quite a few (at busy places like NY, DC, LA, etc). When the aircraft is handed off to another PHYSICAL control facility (such as Tampa TRACON handing off a southerly departure to Miami Center; they're in two separate buildings), the computer assists in this process by printing off a new strip for the other facility, since there is no way to send it other than having someone drive it there.
Thats "knowing who is who" in a nutshell. I'm sure others can add to or correct some things I've said, but it should help you get the idea.