History of Computing

History of Computing http://www.vigneras.name/pierre Dr. Pierre Vignéras This work is licensed under a Creative Commons Attribution-Share Alike 2.0 France. See http://creativecommons.org/licenses/by-sa/2.0/fr/ for details

Text Books Books Reference Book: New Perspectives On Computer Concepts Parsons and Oja National Book Foundation The Web: http://wikipedia.org C- How to program (Third Edition) Introduction C++ and Java Deitel & Deitel Prentice Hall

No entry after the first 10 minutes

No exit before the end of the class

Unannounced Quiz Weekly, at the beginning of a class

Fixed timing (you may suffer if you arrive late)

Spread Out (do it quickly to save your time)

Papers that are not strictly in front of you will be considered as done

Your head should be in front of your paper! Class, Quiz & Exam Rules Rules

A final average below 50/100 will be assigned a failed mark: F. Grading Policy

Outline (Important points) Basics Numeral basis

computer components Hardware History Von Neumann Architecture

Turing Machine, Lambda Calculus & Boolean Algebra

Algorithms (pseudo-code, flowcharts)

Computability and Complexity Theory Language History Compilation vs Interpretation

Type checking (static vs dynamic, weak vs strong) Outline (Important points)

Operating System History Definitions & Compositions

Eras (Unix, Apple, IBM PC, Mac, Windows)

Open Source (GNU, Linux) Network History Internet, Web, Search Engine

Network Topology Outline (Important points)

Computer: definition (http://en.wikipedia.org/wiki/Computer) Origin Person who performed numerical calculations, often with the aid of a mechanical calculating device Today Machine for manipulating data according to a list of instructions known as a program . Various sort Supercomputer, Mainframe, Servers

PDA, Cellular Phones, Smart cards I. Basics

Vocabulary (http://en.wikipedia.org/wiki/Digital http://en.wikipedia.org/wiki/Bit) Digital = discrete Comes from digits (Latin origin = fingers) Analogue = continuous (real life)

Bit = 1 binary digit Can have either the value 1 or 0

Used to represent (almost) everything

Physical representation: 1 == electricity is present

0 == no electricity A byte is a collection of 8 bits Unit for storage capacity I. Basics

Personal Computer Architecture Screen

Memory (http://en.wikipedia.org/wiki/Random_Access_Memory) Random Access Memory (Main memory) Erased when computer is shut down

A list of cells Each cell is assigned an address (a number) and can store a fixed amount of informations (8, 16, 32 or 64 bits) Memory can contains instructions or data The cell addressed #1234 contains “0101”

“0101” may means: the number 5 in decimal,

the instruction: “increase the value of the next cell by one”

The first and third “property” are TRUE, others are FALSE,

Central Processing Unit (Processor) (http://en.wikipedia.org/wiki/CPU) Reads instructions from the memory, executes them and writes the result in the memory Operations possible addition, subtraction, multiplication, division

comparisons, string manipulations, ... Driven by a timer Frequency = Number of ticks (cycle) per second

Performance = Instructions Per Cycle * Frequency AMD Athlon XP ~ 2.5 IPC

At same clock speed, AMD Athlon performs better than Intel PIV Connected with other devices by several bus I. Basics

Input/Output Devices Hard drives Store permanently data Programs and data (documents) Network cards (Ethernet card) Used to connect several computers CD/DVD drives Read-only storage devices (music, video, data) Video Card (3D specialized hardware) Driven by the CPU to transmit data on screen(s)

Contains a Graphic processor (GPU)

Needs its own memory I. Basics

The 2006 market CPUs (future trends is multi-core) Intel: PIV (~ 3.8 GHz), Core Duo (~ 2 GHz)

AMD: Athlon 64, Opteron (~ 2 Ghz) Memory: [512 – 1512] MB

Network Cards: Ethernet: 1 Gb/s

Wireless (Wi-Fi): ~ 54 Mb/s Video Cards: ~ 256 MB, 400 MHz

Screens: CRT 17' & 19'; TFT 15' & 17' (trend) I. Basics

Internet (http://en.wikipedia.org/wiki/Internet) Worldwide, publicly accessible network of interconnected computer networks that transmit data using the IP protocol (language)

World Wide Web (WWW): collection of interconnected documents, linked by Hyperlinks and URLs

accessible via the Internet, as are many other services

You need a client application (called a web browser) URL: protocol://address[:port]/ressource http://images.google.com/preferences (www)

fish://192.168.1.1/documents (SSH) I. Basics

Searching on the web Search Engines Google: http:// www.google.pk

Yahoo: http://www.yahoo.com How does it work? During the night, a robot scans the web and indexes web pages making pairs [word, {URLs}]

When you enter a keyword, the search engine look in its table for a matching [word, {URLs}]

It then present the set of {URLs} Internet does not provide true informations Anyone can write what he wants! I. Basics

E-Mail Works over the Internet like the normal (slow) mail system (also called snail)

You need a client application Can be a web browser (webmail)

Can be a dedicated mail reader You should follow the netiquette (Internet Etiquette) Catch-all term for the conventions of politeness

See: http://tools.ietf.org/html/rfc1855 - RFC1855 (standard) http://www.penmachine.com/techie/emailtrouble_2003-07.html (short) I. Basics

Cryptography Engineering Hardware Processors, Hard drives, Memory, ... Software Design, Operating Systems, Project Management, ... Edsger Dijkstra: " Computer science is no more about computers than astronomy is about telescopes.” Using a computer does not make one a computer scientist! II. History

http://www.eingang.org/Lecture/ II. History

Counting From the very beginning, men started off by counting on their digits for various reasons Sharing food items fairly

Religion & ceremonies according to time

etc. Many possibilities (base): 10, 16, 12, 6, ...

Some attempts to create counting machines Help counting up to big numbers

Abacus (China), Pascaline (Blaise Pascal, 1642), The Difference Engine (Charles Babbage, 1812) II. History/Hardware

Cards 1890: Herman Hollerith presents Punched Cards & Tabulating Machine

Used until the highly controversial United States presidential election of 2000

Tabulating Machine is a great success: creation of IBM by Herman Hollerith Limited to tabulation II. History/Hardware

Cards (http://en.wikipedia.org/wiki/Punch_card) II. History/Hardware

Binary Representation In 1941, Konrad Zuse creates the Z3

Uses binary system II. History/Hardware

Engineering Improvements Mark I (IBM, 1930-1959) Fully automatic machine

Four operations on 23 decimals numbers

Subroutines (logarithm & trigonometric functions)

3 to 5 seconds per multiplication

In use at Harvard until 1959 ENIAC (Mauchly and Eckert, 1946-1955) 10 decimal-digits words

“Wire your own“ instruction technique II. History/Hardware

John Von Neumann (http://en.wikipedia.org/wiki/Von_Neumann_Architecture) Data and Program can be stored in the same space The machine itself can alter either its program or its internal data Conditional goto's to other point in the code

Often used subroutines can be stored in memory

First machine appears in 1947 (EDVAC & UNIVAC) Still the overall architecture of computers today! II. History/Hardware

Von Neumann Architecture II. History/Hardware

Major engineering advances Transistors (Shockley, Bardeen, Walter; 1947) Freedom from vacuum tubes, which were extremely bulky Integrated Circuits (Kilby, 1959) Aka “chip”

collection of tiny transistors which are connected together

only connections were needed to other electronic components Machines becomes smaller and more economical to build and maintain. II. History/Hardware

Moore's Law (http://en.wikipedia.org/wiki/Moore's_law) 1965: Moore, a co-founder of Intel. The complexity of integrated circuits doubles every 24 months

Quoted as “[...] doubles every 18 months ”! Empirical Observations and prediction goal for an entire industry. Moore's law means an average performance improvement in the industry as a whole of over 1% a week. A new product that is expected to take three years to develop and is just two or three months late is 10 to 15% slower, bulkier, or lower in storage capacity! II. History/Hardware

Moore's law II. History/Hardware

Moore's Law effect II. History/Hardware

Moore's Law limitation 2006 state of the art IBM published a paper for a 30 nm technology April 2005 Gordon Moore stated in an interview that the law may not hold valid for too long, since transistors may reach the limits of miniaturization at atomic levels 2003: Kurzweil conjecture Moore's Law of Integrated Circuits was not the first, but the fifth paradigm to provide accelerating price-performance.

New type of technology will replace current integrated-circuit technology, and that Moore's Law will hold true long after 2020. II. History/Hardware

General Moore's Law II. History/Hardware

2006 Trends (http://en.wikipedia.org/wiki/Multicore_CPU) Major misunderstanding: Performance is not equivalent to clock speed !

Moore's law is not about doubling performance anyway! Doubling the number of transistors: Put two CPUs on the same silicon die: dual-core The future is multi-core systems Intel, AMD, IBM, Sun are focusing on this

No need for a new CPU design: less risk Major issue at the software level How to deal with concurrency?

The Godel Theorem (1931) (http://en.wikipedia.org/wiki/Gödel's_incompleteness_theorems) In some cases, it is possible to prove something and its contrary (inconsistency).

Some mathematical truth are impossible to prove (incompleteness) Idea: “Any French is a lier has said by a French”

Sketch of the proof: suppose a program 'P' can tell if a proposition is TRUE or FALSE without error.

Proposition: “The program 'P' does not reply TRUE to this proposition”. Can the program reply TRUE or FALSE? Neither!

And what about us? Is the proposition TRUE? Yes! II. History/Theory

Alan Turing Machine (1936) (http://en.wikipedia.org/wiki/Turing_machine) Infinite tape (divided into adjacent cells) Each cell contains a symbol from some finite alphabet: {a, ..., z}; {0,...,9}; {0,1} Head read/write symbols

move the tape left and right one cell at a time. Table of instructions that tells the machine: what symbol to write

what its new state will be State register that stores the (finite) state of the table. One special start state II. History/Theory

Turing Machine (Abbrev: TM) (http://en.wikipedia.org/wiki/Turing_machine) II. History/Theory

Alan Turing Machine (1936) (http://en.wikipedia.org/wiki/Turing_machine) Stone (1972): fully description requires The alphabet

The input form in which the parameters are presented on the tape

The output form in which answers will be represented on the tape when the Turing machine halts

The initial state of the Turing machine

The machine program II. History/Theory

Turing Machine (http://en.wikipedia.org/wiki/Turing_machine) Example: increment function: inc(x)=x+1 Tape alphabet: {0,1}

Input: A number in base one enclosed by zero 0 10 :0...0 1 0...0 1 10 :0...0 1 10...0 4 10 :0...0 1 11110...0 10 10 :0...0 1 11111111110...0

Output: written in place of the input (same form) 1,>> 0,1 0,>> 1,<< Starting points Starting state II. History/Theory

Turing Machines Turing Machines can be composed to create more complex ones.

Example: f(x)=x+2 II. History/Theory 1,>> 0,1 0,>> 1,<< 1,>> 0,1 0,>> 1,<<

Example: f(x)=x+2 II. History/Theory 1,>> 0,1 0,>> 1,<< 1,>> 0,1 0,>> 1,<< Only one initial state! Only one terminal state! Only one initial state!

Example: f(x)=x+2 II. History/Theory 1,>> 0,1 0,>> 1,<< 1,>> 0,1 0,>> 1,<< Relabel states Make the new link

Turing Machines and Algorithms A Turing Machine describes a “mechanical procedure” Sort of recipe

Each step is simple and well defined so it can be followed by any human using a paper and a pencil Very complex procedures can be described using Turing machines Addition, multiplication, ... (anything?) A Turing machine provides an easy to understand abstraction of how computers (humans or machines) are actually working

Turing Machines are the actual formalisation of what is called algorithms II. History/Theory

Algorithms (http://en.wikipedia.org/wiki/Algorithm) From the famous Arab scientist Al-khwarizmi Solving problems in an ordered step-by-step sequence An algorithm is a finite set of well-defined instructions for accomplishing some task which, given an initial state , will terminate in a defined end-state . Order of computation is usually critical to the functioning of the algorithm.

Instructions are usually listed explicitly starting 'from the top' and going 'down to the bottom': this is what is formally called the flow of control . II. History/Theory

Algorithm Representations A Turing Machine is one representation of an algorithm

Other representations include: Natural language (too verbose and ambiguous)

pseudo code (no standard) derived from programming languages flowcharts (too verbose) schematic representation of a process

derived from Turing Machines representation programming languages (too detailed) So which one to choose? It depends! All of them but for different situations II. History/Theory

Algorithm Example: largest number Natural Language Input: an unsorted list of numbers

Output: the index (rank) of the largest number in the list Assume the first item is largest.

Look at each of the remaining items in the list and if it is larger than the largest item so far, make a note of its rank.

The last noted rank is the one of the largest element in the list when the process is complete. Complexity: requires N comparisons where N is the size of the list II. History/Theory

max = 0 for ( all i such that 0<i<|L|) { if ( L max < L i ) max = i } PRINT L m ax Loop Condition Assignment Output Algorithm Example: largest number Pseudo-code (http://en.wikipedia.org/wiki/Pseudo-code) II. History/Theory Made of statements

Four basic constructions: assignements,

input/output An expression is something that evaluate to a value

max = 0 for ( all i such that 0<i<|L|) { if ( L max < L i ) max = i } PRINT L m ax Loop Condition Assignment Output Algorithm Example: largest number Pseudo-code (http://en.wikipedia.org/wiki/Pseudo-code) II. History/Theory Assignment : left_value = right_value left_value represents the content of a RAM cell '=' means: “ store the value of the expression right_value in left_value ” Not a 'true statement' neither an equation to solve!!

Algorithm Example: largest number Pseudo-code (http://en.wikipedia.org/wiki/Pseudo-code) max = 0 for ( all i such that 0<i<|L|) { if ( L max < L i ) max = i } PRINT L m ax Loop Condition Assignment Output II. History/Theory Condition : two forms If (boolean expression) expression_if_true If (boolean expression) { expression_if_true }else{ expression_if_false }

Boolean Algebra (http://en.wikipedia.org/wiki/Boolean_algebra) Name in honour of George Boole (1825-1864)

Inventor of the Boolean Algebra Consider a set A, supplied with two binary operations ∧ (called AND), ∨ (called OR), a unary operation ¬ (called NOT) and two elements 0 (called zero) and 1 (called one), such that, for all elements a, b and c of set A, the following axioms hold: II. History/Theory a ∨ (b ∨ c) = (a ∨ b) ∨ c associativity a ∧ (b ∧ c) = (a ∧ b) ∧ c a ∨ b = b ∨ a commutativity a ∧ b = b ∧ a a ∨ (a ∧ b) = a absorption a ∧ (a ∨ b) = a a ∨ (b ∧ c) = (a ∨ b) ∧ (a ∨ c) distributivity a ∧ (b ∨ c) = (a ∧ b) ∨ (a ∧ c) a ∨¬ a = 1 complements a ∧¬ a = 0

Boolean Algebra and Logic From that axioms, one can prove some theorem such as: a ∨ 0 = a; a ∧ 1 = a; a ∨ 1 = 1; a ∧ 0 = 0

Interpretation: 0 means “FALSE”, 1 means “TRUE”

A statement 'a' and its contrary cannot both be true: a ∧¬ a = 0 Truth values can be represented as binary numbers or as voltage levels in logic circuits many practical applications in electrical engineering and CS, as well as in maths logic. II. History/Theory

Boolean Expressions In computer science, a boolean expression evaluates only to either TRUE or FALSE Representation of truth values may differ from one language to another C: FALSE = 0, TRUE = ! FALSE

Java: TRUE= true , FALSE= false

LISP: FALSE= '(), TRUE= NOT FALSE, ... A boolean expression can be almost anything... II. History/Theory 3>5 2<3 1 ≤ 1 F T T 1 ≤ 1 AND 2<3 2<3 OR 3>5 NOT 1 ≤ 1 T T F “bye” == “boa” “by” < “bye” NOT “by” F T ? Symbol for comparison in C Symbol for NOT in C

Boolean Operators Table II. History/Theory

Algorithm Example: largest number Pseudo-code (http://en.wikipedia.org/wiki/Pseudo-code) II. History/Theory PRINT “Hello” If (person has a PhD) PRINT “Dr.” PRINT name PRINT “Hello” If (person is a male) { PRINT “Mr.” }else{ PRINT “Mrs.” } PRINT name Execution for Dr.Pierre: “Hello Dr. Pierre” Execution for Mrs. Bhutto “Hello Mrs. Bhutto” Indentation and brackets are very important!

Algorithm Example: largest number Pseudo-code (http://en.wikipedia.org/wiki/Pseudo-code) max = 0 for ( all i such that 0<i<|L|) { if ( L max < L i ) max = i } PRINT m ax Loop Condition Assignment Output II. History/Theory Loop : many forms For (variable in “a finite set of values”) expression While (boolean expression) expression Do { expression } while (boolean expression) In all forms, you have a stop condition

History of Computing

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