The Fourth Generation Computers (1976-present)

The advent of the microprocessor chip marked the beginning of the fourth generation computers. Medium scale integrated (MSI) circuits yielded to Large and Very Large Scale Integrated (VLSI) circuits packing about 50000 transistors in a chip. (Today even VVLSI circuits are being developed.) Semiconductor memories replaced magnetic core memories. The emergence of the microprocessor (CPU on a single chip) led to the emergence of extremely powerful personal computers. Computer costs came down so rapidly that these found places in most offices and homes. The faster accessing and processing speeds and increased memory capacity helped in development of much more powerful operating systems.
The second decade (1986-present) of the fourth generation observed a great increase in the speed of microprocessors and the size of main memory. The speed of microprocessors and the size of main memory and hard disk went up by a factor of 4 every 3 years. Many of the mainframe CPU features became part of the microprocessor architecture in 90s. In 1995 the most popular CPUs were Pentium, Power PC etc. Also RISC (Reduced Instruction Set Computers) microprocessors are preferred in powerful servers for numeric computing and file services.