History of Regular Expression

Regular expressions are set of symbols to find patterns in strings, its not a programming language.

Knowing the history of regular expression help us to have a better understanding of some key points in the way regular expression works. Surprisingly, the idea was not originated in the field of computer science. It finds, its way into computer science from neuroscience.

In 1943, McCulloch and Pitts developed models describing how the human neverous system works [1] which was extended by Stephen Kleene in 1956, he described these models with an algebra notation that he called regular sets/regular expression.

In 1968, Ken Thompson a mathematician and one of the key developers of UNIX implemented regular expression inside the text editor called ed. That is the entry point of regX into computing world.
Ed Text Editor & History of Grep command: Ed has the functionality to search based on regular expression. For instance: The command like below was used to search for the word “pinky” in a text document.

g/pinky/p i.e.(g/regular expression/p)

g and p are modifiers where g was telling the editor to search for the word through out the document and p was to print the results to the screen; global regular expression print, in short now we are calling it as grep.