What is a Computer

1
What is a Computer?
2
Hardware
Central Processor Unit
Control Unit Arithmetic-Logic Unit (ALU)
Internal Storage
Input device
Output device
3
What is Computer Science?
4
What are we studying?
Theory
Architecture
Language
Hardware
Software
5
What is it, really?
Computer! Computer! Computer!
6
Computer --
A machine that can Compute!
What is a machine?
A machine is a device that follows a certain
fixed causal rules.
What is Computation?
A computation is a sequence of procedures that
manipulate data.
7
Brains are Machines!!
Body
Mind
Image from http//www-groups.dcs.st-and.ac.uk/hi
story/PictDisplay/Descartes.html
8
Lets Compute!!
Gottfried W.V Leibniz (1646-1716)
Sir! Lets sit down and compute!!
Image from http//sunsite.informatik.rwth-aachen.
de/phil/filosofer/leibniz.html
9
Real Life
There any tons of problems that cant be solved
by computers?
Ideal Life
Are there any problems that cant be solved by
any computation?
10
Alan Turing (1912-1954)
The Enigma
The man who invented the computer.
Image from http//ei.cs.vt.edu/history/Turing.htm
l
11
Turing Machine
1. A Tape (infinite)
2. A fixed finite set of symbols (0,1)
3. Four actions read/write symbols from/onto
the tape, move the tape back/forwards.
4. A finite transition table
And, that is enough to beat any Super-Computer!!
12
Wittgenstein says
Ludwig Wittgenstein (1889-1951)

• Turing Machines are human that compute.

In logic nothing is accidental
Image from http//www.ags.uci.edu/bcarver/wgaller
y.html