In 1987, Thomas Peterffy, an options trader with a background in software, sliced a cable feeding data to his Nasdaq terminal and hacked it into the back of a computer. The result was a fully automated algorithmic trading system, in which Peterffy's software received quotes, analysed them and executed trades without any need for human intervention.
Not long after, a senior Nasdaq official dropped by at Peterffy's office to meet what he assumed must be a large team of traders. The official was alarmed to be shown that the entire operation comprised a Nasdaq terminal sitting alongside a single, silent computer.
From such humble beginnings, computerised trading has become very big business. High-frequency trades take place on timescales measured in microseconds - for comparison, Usain Bolt's reaction time in the Olympic 100m final was 165,000 microseconds.