Structure of the U. S. Air Traffic Control System

Air Traffic control facilities (ARTCC) are organized into three specialties

1. Air Route Traffic Control Centers (ARTCC) - high altitude en-route traffic

The ATC Centers used IBM 9020 computers starting in 1967. This was hot in its day. The 9020 was a an IBM mainframe. Here is a link to the Stanford U. IBM 9020 page   and FAA ARTCC computers  Most of the guys that maintained this software are long retired. The IBM 9020 was programmed in BAL and Jovial which are pretty cool languages. ARTCCs had their own "cowboys"

2. Radar Approach Control - Also known as the "Terminal Radar Approach Control (Tracon)" handles traffic around an airport roughly 40 nautical mile radius and up to 10,000 to 20,000 plus feet above the surface.

There were two main systems  in use in the dawn of ATC Automation:  ARTS IIIA which was utilized for high traffic airports from the early 1970's, then a within a couple of years, a system known as ARTS IIA was implemented for medium to low traffic airports. Smaller airports without radar normally do not have an automation system, although this is changing with the increase in technology that makes remote operation viable. These systems have been replaced by newer "unix like OS's" using Motorola chips or Sun machines. These are already considered legacy systems from the moment of their implementation.

3. Tower - handles the traffic within about 5 - 10 miles from the airport and is responsible for maintaining separation of aircraft on runways and taxiways
Since the Tower is generally co-located with the Approach control it uses the same automation system. More info here about tower controllers. In some facilities controllers work both radar and tower control.

Simulated radar display showing "Data blocks", that provide pertinent information to the controller, such as Aircraft ID, Mode-C altitude (3 digits) and ground speed (2 digits). Altitude is given in hundreds of feet and ground speed in tens of knots.

Note UAL329 at 18000 feet and 270 knots

Simulated radar display. The lines are airspace boundarys, final approach courses, fixes, obstructions (tall antennas or buildings) etc

Alone in a sea of non-programmers
Home ATC Automation Part 1 ATC Automation Part 2 ATC Automation Part 3 Scatter Scatter Part 4 Radar Handoff - part 5 The Tower Controller