3rd generation computers

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					   The 3rd Generation Computers were generally much smaller in size than the 2nd and 1st
generation computers. This is because these newer computers made us of integrated circuits and
semiconductors (a type of material that had the properties of an insulator and a conductor). 3rd
    generation computers also contained operating systems, which acted as overseers to the
  performance of a computer and which allowed computers to run different programs at once.
Another function of operating systems is to make sure everything is flowing smoothly inside the
  computer. The 3rd generation computers made the transition from transistors to integrated
                circuits and from punch cards to electronic computer systems.

1964-1965: IBM 360
The IBM 360 was introduced by IBM (duh!) in April of 1964, and was finally delivered in 1965. It was
not actually a single computer, but was rather a family of six computers and their peripherals. These
computers were all mutually compatible and all worked together. The first models of the IBM 360 used
transistors, but later these computers made a transition from transistors to integrated circuits.

1965: PDP-8
The PDP-8 was a successor to the PDP-1. Because it was the first computer to successfully make use of
integrated circuits, it was much smaller and cheaper compared to other computers available at the same
time. When it first entered the minicomputer market, it sold for about $20,000. Five years later, this
price was reduced to only $3,000. The PDP-8 was relativelysimple in design-physically, logically, and
electronically. It only had 4,096 words of memory, and its word length was only 12 bits. This machine
became the first commercially successful minicomputer because of its reasonable cost, speed, and
small size. Minicomputers are medium-sized computers that were much cheaper than the larger and
bulkier mainframe computers.

1966: HP-2115
With the invention of the HP-2115, the company Hewlett Packard enters the computer business.

1969: UNIX
At the AT & T Bell Laboratories, programmers Kenneth Thompson and Dennis Ritchie developed a
new type of operating system known as UNIX. UNIX is a multi-user operating system able to perform
multiple tasks. In addition, UNIX is written in the C language, which allows it to be less machine-
specific than other available operating systems. C was specifically designed for UNIX. Because UNIX
used C, it was able to be used in any computer system. This was a big achievement at the time!

1970s: GUI
GUI (graphical user interface, pronounced gooey) was designed by the Xerox Corporation. GUI
allowed users to be able to "point and click." In other words, the computer screen was designed to
resemble a desktop. It had click-able folders, calculators, etc. which were represented by images known
as icons. Users could click on these icons to move and manipulate the folders and other tools. GUI
made using computers much easier and is currently found in modern-day computers.

                           Third Generation Computers (1963-1972)

 The third generation brought huge gains in computational power. Innovations in this era include
the use of integrated circuits, or ICs (semiconductor devices with several transistors built into one
physical component), semiconductor memories starting to be used instead of magnetic cores,
microprogramming as a technique for efficiently designing complex processors, the coming of age
of pipelining and other forms of parallel processing (described in detail in Chapter CA), and the
introduction of operating systems and time-sharing The first ICs were based on small-scale
integration (SSI) circuits, which had around 10 devices per circuit (or "chip"), and evolved to the
use of medium-scale integrated (MSI) circuits, which had up to 100 devices per chip. Multilayered
printed circuits were developed and core memory was replaced by faster, solid state memories.
Computer designers began to take advantage of parallelism by using multiple functional units,
overlapping CPU and I/O operations, and pipelining (internal parallelism) in both the instruction
stream and the data stream. In 1964, Seymour Cray developed the CDC 6600, which was the first
architecture to use functional parallelism. By using 10 separate functional units that could operate
simultaneously and 32 independent memory banks, the CDC 6600 was able to attain a computation
rate of 1 million floating point operations per second (1 Mflops)

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