Fundamental concepts of Information...

Fundamental concepts of Information Technology

A brief history, the Neumann architecture, the language of computers

Csernyi Gabor

Department of English LinguisticsUniversity of Debrecen

Csernyi Gabor (DE IEAS) Fundamental concepts of IT 1 / 17

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


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 Janos andHermann Goldstine: ENIAC machine (Neumann’s importance!)

Neumann & Goldstine: the formulation of the requirements of theelectronic digital computer Ô the (von-)Neumann principles

storage: punch card, tape

huge computers with high energy consumption, air conditionersneeded to reduce heat produced by computers

warm-up time

electric failures

lower-level programming, machine language



Second generation (∼ 1955-64):

invention of transistor: Walter Brattain, John Bardeen & WilliamShockley (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



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 anintegrated chip will double every year (1965)) still holds



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)



Fifth generation (∼ mid-1990s-):

artificial intelligence, problem solving

expert systems

robotics

natural language


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 astored program machine.

5 Universal computer.


The conceptual architecture of computers


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, basicmathematical operations (adding, multiplying).


Logic gates (1)

Statements: true / false1: true0: false

NOT:

A NOT A

1 0

0 1


Logic gates (2)

AND:

A B A AND B

1 0 0

1 1 1

0 0 0

0 1 0


Logic gates (3)

OR:

A B A OR B

1 0 1

1 1 1

0 0 0

0 1 1


Logic gates (4)

XOR (exclusive OR):

A B A XOR B

1 0 1

1 1 0

0 0 0

0 1 1


Representing text (1)

1 BCD (Binary Coded Decimal)4 bits for each decimal (3 bits would not be enough; the maximumnumber that can be represented with 4 bits is23 + 22 + 21 + 20 = 15)

e.g.: 127 = 0001 0010 01111 2 7



2 EBCDIC (Extended Binary Coded Decimal Interchange Code)the extension of BCD: additional four bits, the first four called thezone (which group the character is in), the second four called thedigit (the code of the character)



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 alphabetmaximum of 127 characters can be represented(=7 bits Ô 26 + 25 + . . . + 20 = 127)

I later extended: 8 bits used for representation, to code letters notincluded in the English alphabet (+128 characters can be coded) thisadditional bit is used for defining code pages+ problematic issue: inconsistency (two different characters with thesame code in two different code pages)+ solution: UNICODE

F number of bits used for representation: 16 (65536 characters can berepresented!), then extended to 32

F advantage: no code pages, consistent among languages


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