Fourth Generation of Computers
The fourth generation of computers began around 1975 and lasted until around 1985. It recognizes that period of computer history when the integrated circuit chip evolved into the microprocessor, a “computer on a chip.” As a result, the first functional desktop computers came into being, beginning with the hobbyist DIY experimental models, such as the Altair 8800 mail-order kit, and progressing to the early commercial models such as the Commodore and the Tandy TRS-80. The period marks the successful introduction and mass production of the early desktop models of the IBM PC, its several clones, and the Apple Macintosh.
A star of the previous generation of computers had been the 1960s Control Data CD 1604 computer. In order to process data it had some 25,000 transistors and 100,000 diodes among thousands of resistors and capacitors, all individually wired together.
The microprocessor was in route to do all the things the CD 1604 did on one chip. It had its birth when researchers at Intel integrated all the processing functions of arithmetic, logic, and control together onto one chip through a process of photolithography.
The CPU read the data and instructions that came in as bytes of 8-bit code. The reading involved performing arithmetic and logic calculations on the code. The resulting data and instructions further allowed control functions to order the code into various streams of data that were written or received as graphics output on a monitor.
The integrated microprocessor chip became known as the central processing unit — the CPU — or the “brains” of the model computer. Its entrance heightened the earlier 1958-1959 inventions of the integrated circuit chip by Jack Kilby, at Texas Instruments, and Robert Noyce, then at Fairchild Semiconductor. These two engineers had independently miniaturized the transistor and created the IC chip as a solid-state piece of silicon (or germanium). Their discoveries had essentially brought in the new age of solid-state electronics.
Kilby received the Nobel Prize for the IC chip while Noyce continued its development as founder of the Intel Corporation. Meanwhile, the solid state miniaturization of electronic components immediately pushed technology into new bounds of advances in space, defense and consumer projects. By the 1970s, large-scale integration (LSI) of tens of thousands of transistors on one chip would eventually lead to very-large-scale integration (VLSI) with millions and, then, billions of transistors per chip after the turn of the century.
