Fundamental concepts of Information Technology
A brief history, the Neumann architecture, the language of computers
Csernyi Gábor
Department of English Linguistics
University of Debrecen
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Table of contents
1
A brief history
Computer generations
2
The Neumann architecture
The Neumann-principles
The conceptual architecture of computers
3
The language of computers
Representing numbers
Logic gates
Representing text
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A short history: computer generations (1)
First generation (∼ 1946-54):
development of the vacuum tube: Lee de Forest (1906)
Presper Eckert and John Mauchly, together with Neumann János and
Hermann Goldstine: ENIAC machine (Neumann’s importance!)
Neumann & Goldstine: the formulation of the requirements of the
electronic digital computer Ô the (von-)Neumann principles
storage: punch card, tape
huge computers with high energy consumption, air conditioners
needed to reduce heat produced by computers
warm-up time
electric failures
lower-level programming, machine language
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A short history: computer generations (2)
Second generation (∼ 1955-64):
invention of transistor: Walter Brattain, John Bardeen & William
Shockley (1947)
compared to the vacuum tube:
I
less energy consumption, less heat
I
smaller but faster
I
higher reliability
I
no warm-up time
storage devices: removable disk, magnetic tape
the development of the first high-level programming language:
FORTRAN
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A short history: computer generations (3)
Third generation (∼ 1965-74):
development of IC (integrated circuit): Jack Kilby & Robert Noyce
(1959)
electronic circuit on silicon chip
magnetic core memory replaced by microchip
operating systems
keyboard, screen
mass production
Intel (INTegated ELectronics) (1968)
small-scale integration (SSI), medium-scale integration (MSI)
Gordon Moore’s prediction (that the number of transistors on an
integrated chip will double every year (1965)) still holds
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A short history: computer generations (4)
Fourth generation (∼ 1974-mid-1990s):
nanotechnology
microprocessor
parallel processing
first IBM PCs (1981) and Apple computers (1983)
graphical user interface (GUI)
small and faster integrated circuits
higher capacity memory types
large-scale integration (LSI)
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A short history: computer generations (5)
Fifth generation (∼ mid-1990s-):
artificial intelligence, problem solving
expert systems
robotics
natural language
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The Neumann-principles
1
Executing the instructions sequentially.
also note: multiprocessor computers
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The Neumann-principles
1
Executing the instructions sequentially.
also note: multiprocessor computers
2
Completely electronic computer, using the binary system.
lower voltage: 0; higher voltage: 1
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The Neumann-principles
1
Executing the instructions sequentially.
also note: multiprocessor computers
2
Completely electronic computer, using the binary system.
lower voltage: 0; higher voltage: 1
3
Internal memory.
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The Neumann-principles
1
Executing the instructions sequentially.
also note: multiprocessor computers
2
Completely electronic computer, using the binary system.
lower voltage: 0; higher voltage: 1
3
Internal memory.
4
Program is stored in the (same) memory as data: the computer is a
stored program machine.
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The Neumann-principles
1
Executing the instructions sequentially.
also note: multiprocessor computers
2
Completely electronic computer, using the binary system.
lower voltage: 0; higher voltage: 1
3
Internal memory.
4
Program is stored in the (same) memory as data: the computer is a
stored program machine.
5
Universal computer.
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The conceptual architecture of computers
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Representing data
Number systems:
ternary (base 4) digits: 0-3
octal (base 8) digits: 0-7
decimal (base 10) digits: 0-9
hexadecimal (base 16) digits: 0-9, A-F
Neumann principles Ô computers use the binary number system.
practice
Representatoin, conversion from one number system to another, basic
mathematical operations (adding, multiplying).
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Logic gates (1)
Statements: true / false
1: true
0: false
NOT:
A
1
0
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NOT A
0
1
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Logic gates (2)
AND:
A
1
1
0
0
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B
0
1
0
1
A AND B
0
1
0
0
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Logic gates (3)
OR:
A
1
1
0
0
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B
0
1
0
1
A OR B
1
1
0
1
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Logic gates (4)
XOR (exclusive OR):
A
1
1
0
0
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B
0
1
0
1
A XOR B
1
0
0
1
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Representing text (1)
1
BCD (Binary Coded Decimal)
4 bits for each decimal (3 bits would not be enough; the maximum
number that can be represented with 4 bits is
23 + 22 + 21 + 20 = 15)
e.g.: 127 = 0001
1
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0010
2
0111
7
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Representing text (2)
2
EBCDIC (Extended Binary Coded Decimal Interchange Code)
the extension of BCD: additional four bits, the first four called the
zone (which group the character is in), the second four called the
digit (the code of the character)
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Representing text (3)
3
ASCII (American Standard Code for Information Interchange)
I
the original version used 7 bits for representation: to code numbers,
control characters (e.g.: return), and letters of the English alphabet
maximum of 127 characters can be represented
(=7 bits Ô 26 + 25 + . . . + 20 = 127)
I
later extended: 8 bits used for representation, to code letters not
included in the English alphabet (+128 characters can be coded) this
additional bit is used for defining code pages
+ problematic issue: inconsistency (two different characters with the
same code in two different code pages)
+ solution: UNICODE
F
number of bits used for representation: 16 (65536 characters can be
represented!), then extended to 32
F
advantage: no code pages, consistent among languages
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