By the middle of the 20th century, automation had existed for many years on a small scale, using mechanical devices to automate the production of simply shaped items. However the concept only became truly practical with the addition of the computer, whose flexibility allowed it to drive almost any sort of task. Computers with the required combination of power, price, and size first started to appear in the 1960s, and since then have taken over the vast majority of assembly line tasks (some food production/inspection being a notable exception).
In most cases specialised hardened computers refered to as PLCs (Programmable Logic Controllers) are used to synchronize the flow of inputs from sensors and events with the flow of outputs to actuators and events. This leads to precisely controled actions that permit a tight control of the process or machine.
HMIs (Human-Machine Interfaces) are usually employed to communicate to PLCs. e.g.: To enter and monitor temperatures or pressures to be maintained.
Some argue automation leads to fuller employment. One author made that case here: When automation was first introduced, it caused widespread fear. It was thought that the displacement of human workers by computerized systems would lead to unemployment (this also happened with mechanization, centuries earlier). In fact the opposite was true, the freeing up of the labor force allowed more people to enter information jobs, which are typically higher paying. One odd side effect of this shift is that "unskilled labor" now pays very well in most industrialized nations, because fewer people are available to fill such jobs leading to supply and demand issues.
Some argue the reverse, at least in the long term. First, automation has only just begun and short-term conditions might partially obscure its long-term impact. For instance many manufacturing jobs left the United States during the early 1990s, but a massive upscaling of IT jobs at the same time offset this as a whole.
It appears that automation does devalue unskilled labor through its replacement with less-expensive machines, however the overall effect of this on the workforce as a whole remains unclear. Today automation of the workforce in the "western world" is quite advanced, yet during the same period the general wellbeing of its citizens has increased dramatically. What role automation played in these chanes has not been well studied.
See also: industrial data processing, domotics, luddism