Evolution of os

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•First Digital Computer was designed by Charles Babbage(1792-1871) called Analytical Engine.

•Design was purely mechanical (wheels, gears, cogs etc)

•Due to Unreliable design did not get popular.

•It did not have any Operating System.

•Around 1940’s John Von Neumann and others developed Calculating Engine.

•Initially they used mechanical Relays but was very slow.

•Replaced by vacuum tubes.

•Machines were enormous, Entire Room Sized, With Tens of thousands of vacuum tubes.

•Still millions times slower than today’s cheapest PC.

•Programming was done in machine language.

•Often by wiring up the plug boards to control the machine’s basic functions.

•Programming languages were unknown.

•Operating systems were unheard of.


•Programmers have to sign up for a block of time

•Come down to the machine room

•Insert his or her plug board into the computer.

•Spend the next few hours hoping that none of the thousands of vacuum tubes would burn out during the programs run.

•Just numerical calculations were performed.

•In 1950 punch cards were Introduced instead of plug boards.

•In 1950s Transistors were introduced.

•Computers were reliable enough to be manufactured and sold.

•Machines were called Mainframes, locked in a special air conditioned room with the professional operators to operate them.

•Only big companies or major govt. agencies or universities could afford the multimillion dollar price equipment.

•To run a job

•Write program on paper (FORTRAN or Assembler) then punch it on punch cards.

•Bring card deck to the computer room and hand it over to the operator. (Wait for Output)

•When Job gets finished, operator takes print out and brings to the output room and then programmer can collect it.

•During the Job if FORTRAN compiler needed then?

•Perform Next Job.

•Much Computer Time was wasted while Operators were moving around the machine room.

•High Cost Equipment, How to reduce the Wasted Time?

•Solution was Batch System.


•Idea was to collect a tray full of jobs in the Input room.

•Read Jobs onto a magnetic tape using a small inexpensive computer IBM 1401, was very good at reading cards, copying tapes & printing output. (was not good at numerical calculations)

•Other much more expensive machines, IBM 7904, were used for real computing.


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