Information Age
1947–1969: Origins

In 1947, the first working transistor, the germanium -based point-contact transistor, was invented by John Bardeen and Walter Houser Brattain while working under William Shockley at Bell Labs. This led the way to more advanced digital computers. From the late 1940s, universities, military, and businesses developed computer systems to digitally replicate and automate previously manually performed mathematical calculations, with the LEO being the first commercially available general-purpose computer.

Digital communication became economical for widespread adoption after the invention of the personal computer in the 1970s. Claude Shannon, a Bell Labs mathematician, is credited for having laid out the foundations of digitalization in his pioneering 1948 article, A Mathematical Theory of Communication.

Other important technological developments included the invention of the monolithic integrated circuit chip by Robert Noyce at Fairchild Semiconductor in 1959 (made possible by the planar process developed by Jean Hoerni), the first successful metal–oxide–semiconductor field-effect transistor (MOSFET, or MOS transistor) by Mohamed Atalla and Dawon Kahng at Bell Labs in 1959, and the development of the complementary MOS (CMOS) process by Frank Wanlass and Chih-Tang Sah at Fairchild in 1963.

In 1962 AT&T deployed the T-carrier for long-haul pulse-code modulation (PCM) digital voice transmission. The T1 format carried 24 pulse-code modulated, time-division multiplexed speech signals each encoded in 64 kbit/s streams, leaving 8 kbit/s of framing information which facilitated the synchronization and demultiplexing at the receiver. Over the subsequent decades the digitisation of voice became the norm for all but the last mile (where analogue continued to be the norm right into the late 1990s).

Following the development of MOS integrated circuit chips in the early 1960s, MOS chips reached higher transistor density and lower manufacturing costs than bipolar integrated circuits by 1964. MOS chips further increased in complexity at a rate predicted by Moore's law, leading to large-scale integration (LSI) with hundreds of transistors on a single MOS chip by the late 1960s. The application of MOS LSI chips to computing was the basis for the first microprocessors, as engineers began recognizing that a complete computer processor could be contained on a single MOS LSI chip. In 1968, Fairchild engineer Federico Faggin improved MOS technology with his development of the silicon-gate MOS chip, which he later used to develop the Intel 4004, the first single-chip microprocessor. It was released by Intel in 1971, and laid the foundations for the microcomputer revolution that began in the 1970s.

MOS technology also led to the development of semiconductor image sensors suitable for digital cameras. The first such image sensor was the charge-coupled device, developed by Willard S. Boyle and George E. Smith at Bell Labs in 1969, based on MOS capacitor technology.
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