*See picture below*
The new Doodle (see screengrab below) has been posted in celebration of the 57th anniversary of the invention of the barcode, which was created by Norman Woodland and Bernard Silver, who filed for a patent in October 1949.
The Washington Post explains how the Google barcode logo has been encoded:
The barcode on the Google homepage is Code 128 encoded, which is a standard way of encoding ASCII character strings (ie. A-Z, a-z, 0-9, etc.) into a barcode. It would be safe to assume that Google used their own open source barcode project, ZXing, to generate the barcode. The same library is used in Android for barcode recognition.
Recently, Google has also commemorated Mahatma Gandhi on his 140th birthday, as well as writer H.G. Wells, on what would have been his 143rd birthday.
Barcodes were first used to label railroad cars, but did not catch on, or become comercially viable, until they were adopted for use in automating payment in supermarkets and other retail stores.
Interestingly, Silver's inspiration for the barcode came from Morse code. According to Wikipedia,
[Silver] formed his first barcode from sand on the beach when "I just extended the dots and dashes downwards and made narrow lines and wide lines out of them." To read them, he adapted technology from optical soundtracks in movies, using a 500-watt light bulb shining through the paper onto an RCA935 photomultiplier tube (from a movie projector) on the far side. He later decided that the system would work better if it were printed as a circle instead of a line, allowing it to be scanned in any direction.