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CSC 221: Introduction to Programming Fall 2012

Computer basics and history hardware vs. software generations of computer technology evolution of programming why Python?. CSC 221: Introduction to Programming Fall 2012. hardware vs. software.

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CSC 221: Introduction to Programming Fall 2012

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  1. Computer basics and history hardware vs. software generations of computer technology evolution of programming why Python? CSC 221: Introduction to ProgrammingFall 2012

  2. hardware vs. software • The easiest way to tell the difference between hardware and software is to kick it. If it hurts your toe, it’s hardware. • Carl Farrell • basic terminology: • hardware – the physical components of the computer e.g., processor (Intel Core i5, AMD A6, Intel Pentium Mobile) memory (RAM, cache, hard drive, floppy drive, flash stick) input/output devices (keyboard, mouse, monitor, speaker) • software – programs that run on the hardware e.g., operating system (Windows 7, Mac OS X, Linux) applications (Word, Excel, PowerPoint, RealPlayer, IE, Firefox) development tools (JDK, BlueJ, .NET, IDLE, Scratch)

  3. History of computing technology • DYK? When were "modern" computers invented? When were computers accessible/affordable to individuals? When was the Internet born? When was the Web invented? How did Bill Gates get so rich? • the history of computers can be divided into generations, with • each generation defined by a technological breakthrough • 0. gears and relays •  1. vacuum tubes •  2. transistors •  3. integrated circuits •  4. very large scale integration •  5. parallel processing & networking

  4. Generation 0: Mechanical Computers • 1642 – Pascal built a mechanical calculating machine • used mechanical gears, a hand-crank, dials and knobs • other similar machines followed • 1805 – the first programmable device was Jacquard's loom • the loom wove tapestries with elaborate, programmable patterns • a pattern was represented by metal punch-cards, fed into the loom • using the loom, it became possible to mass-produce tapestries, and even reprogram it to produce different patterns simply by changing the cards • mid 1800's – Babbage designed his "analytical engine" • its design expanded upon mechanical calculators, but was programmable via punch-cards (similar to Jacquard's loom) • Babbage's vision described the general layout of modern computers • he never completed a functional machine – his design was beyond the technology of the day

  5. Generation 0 (cont.) • 1930's – several engineers independently built "computers" using electromagnetic relays • an electromagnetic relay is physical switch, which can be opened/closed via electrical current • relays were used extensively in early telephone exchanges • Zuse (Nazi Germany) – his machines were destroyed in WWII • Atanasoff (Iowa State) – built a partially-working machine with his grad student • Stibitz (Bell Labs) – built the MARK I computer that followed the designs of Babbage • limited capabilities by modern standards: could store only 72 numbers, required 1/10 sec to add, 6 sec to multiply • still, 100 times faster than previous technology

  6. Generation 1: Vacuum Tubes • mid 1940's – vacuum tubes replaced relays • a vacuum tube is a light bulb containing a partial vacuum to speed electron flow • vacuum tubes could control the flow of electricity faster than relays since they had no moving parts • invented by Lee de Forest in 1906 • 1940's – hybrid computers using vacuum tubes and relays were built • COLOSSUS (1943) • first "electronic computer", built by the British govt. (based on designs by Alan Turing) • used to decode Nazi communications during the war • the computer was top-secret, so did not influence other researchers • ENIAC (1946) • first publicly-acknowledged "electronic computer", built by Eckert & Mauchly (UPenn) • contained 18,000 vacuum tubes and 1,500 relays • weighed 30 tons, consumed 140 kwatts

  7. Generation 1 (cont.) • COLOSSUS and ENIAC were not general purpose computers • could enter input using dials & knobs, paper tape • but to perform a different computation, needed to reconfigure • von Neumann popularized the idea of a "stored program" computer • Memory stores both data and programs • Central Processing Unit (CPU) executes by loading program instructions from memory and executing them in sequence • Input/Output devices allow for interaction with the user • virtually all modern machines follow this • von Neumann Architecture • (note: same basic design as Babbage) • programming was still difficult and tedious • each machine had its own machine language, 0's & 1's corresponding to the settings of physical components • in 1950's, assembly languages replaced 0's & 1's with mnemonic names • e.g., ADD instead of 00101110

  8. Generation 2: Transistors • mid 1950's – transistors began to replace tubes • a transistor is a piece of silicon whose conductivity can be turned on and off using an electric current • they performed the same switching function of vacuum tubes, but were smaller, faster, more reliable, and cheaper to mass produce • invented by Bardeen, Brattain, & Shockley in 1948 (earning them the 1956 Nobel Prize in physics) some historians claim the transistor was the most important invention of the 20th century • computers became commercial as cost dropped • high-level languages were designed to make programming more natural • FORTRAN (1957, Backus at IBM) • LISP (1959, McCarthy at MIT) • BASIC (1959, Kemeny at Dartmouth) • COBOL (1960, Murray-Hopper at DOD) • the computer industry grew as businesses could afford to • buy and use computers • Eckert-Mauchly (1951), DEC (1957) • IBM became market force in 1960's

  9. Generation 3: Integrated Circuits • mid 1960's - integrated circuits (IC) were produced • Noyce and Kilby independently developed techniques for packaging transistors and circuitry on a silicon chip (Kilby won the 2000 Nobel Prize in physics) • this advance was made possible by miniaturization & improved manufacturing • allowed for mass-producing useful circuitry 1971 – Intel marketed the first microprocessor, the 4004, a chip with all the circuitry for a calculator • 1960's saw the rise of Operating Systems • recall: an operating system is a collection of programs that manage peripheral devices and other resources • in the 60's, operating systems enabled time-sharing, where users share a computer by swapping jobs in and out • as computers became affordable to small businesses, specialized programming languages were developed • Pascal (1971, Wirth), C (1972, Ritchie)

  10. Generation 4: VLSI • late 1970's - Very Large Scale Integration (VLSI) • by the late 1970's, manufacturing advances allowed placing hundreds of thousands of transistors w/ circuitry on a chip • this "very large scale integration" resulted in mass-produced microprocessors and other useful IC's • since computers could be constructed by simply connecting powerful IC's and peripheral devices, they were easier to make and more affordable

  11. Generation 4: VLSI (cont.) • with VLSI came the rise of personal computing • 1975 - Bill Gates & Paul Allen founded Microsoft • Gates wrote a BASIC interpreter for the first PC (Altair) • 1977 - Steve Wozniak & Steve Jobs founded Apple • went from Jobs' garage to $120 million in sales by 1980 • 1980 - IBM introduced PC • Microsoft licensed the DOS operating system to IBM • 1984 - Apple countered with Macintosh • introduced the modern GUI-based OS (which was mostly developed at Xerox) • 1985 - Microsoft countered with Windows • 1980's - object-oriented programming began • represented a new approach to program design which views a program as a collection of interacting software objects that model real-world entities • Smalltalk (Kay, 1980), C++ (Stroustrup, 1985), Java (Sun, 1995)

  12. Generation 5: Parallelism/Networks • the latest generation of computers is still hotly debated • no new switching technologies, but changes in usage have occurred • parallel processing has become widespread • multi-core processors provide simple parallelism, can spread jobs across cores • similarly, high-end machines (e.g. Web servers) can have multiple CPU's • in 1997, highly parallel Deep Blue beat Kasparov in a chess match • most computers today are networked • the Internet traces its roots to the 1969 ARPANet • mainly used by government & universities until the late 80s/early 90s • the Web was invented by Tim Berners-Lee in 1989, to allow physics researchers to share data • 1993: Marc Andreessen & Eric Bina developed Mosaic • 1994: Andreesen & Netscape released Navigator • 1995: Microsoft released Internet Explorer • in 2009, 55% of American adults connected to Internet wirelessly, >30% using a smart phone (Internet Software Consortium & Netcraft, April 2010.)

  13. Computing entrepreneurs

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Evolution of programming: machine language • late 40’s / early 50’s: programmers coded directly in machine language • each machine had its own set of instructions (sequences of 0's & 1's) corresponding to its underlying hardware  extremely tedious, error-prone

  15. Evolution of programming: assembly language gcc2_compiled.: .global _Q_qtod .section ".rodata" .align 8 .LLC0: .asciz "Hello world!" .section ".text" .align 4 .global main .type main,#function .proc 04 main: !#PROLOGUE# 0 save %sp,-112,%sp !#PROLOGUE# 1 sethi %hi(cout),%o1 or %o1,%lo(cout),%o0 sethi %hi(.LLC0),%o2 or %o2,%lo(.LLC0),%o1 call __ls__7ostreamPCc,0 nop mov %o0,%l0 mov %l0,%o0 sethi %hi(endl__FR7ostream),%o2 or %o2,%lo(endl__FR7ostream),%o1 call __ls__7ostreamPFR7ostream_R7ostream,0 nop mov 0,%i0 b .LL230 nop .LL230: ret restore .LLfe1: .size main,.LLfe1-main .ident "GCC: (GNU) 2.7.2" • mid 1950’s: assembly languages replaced numeric codes with mnemonic names • an assembler is a program that translates assembly code into machine code • input: assembly language program • output: machine language program • still low-level & machine-specific, but easier to program

  16. Evolution of programming: high-level language • late 1950's – present: • high-level languages allow the • programmer to think at a • higher-level of abstraction • a compiler is a program that translates high-level code into machine code • input: C language program • output: machine language program • similar to assembler, but more complex • an interpreter is a program that reads and executes each language statement in sequence • Python programs are first compiled into a virtual machine language (bytecode) • then the bytecode is executed by an interpreter (Python Virtual Machine) /* Hello World in C */ #include<stdio.h> main() { printf("Hello World"); } def HelloWorld(): """ Simple Python function that displays a message """ print "Hello World!" HelloWorld()

  17. Why Python? • Python is a simple, but industry-strength, scripting language • very simple language, designed for getting things to work with minimal overhead • can be used for rapid development, but also supports object-oriented programming • scripting languages (e.g., Python, PHP, perl, JavaScript) are growing in popularity • note: we will be using Python 3 (not 2)

  18. If you want to know more… • check out the following (purely optional) links Inventors: The History of Computers Computer Museum History Center Transistorized! from PBS.org Apple Computer Reading List The History of Microsoft Internet Pioneers: Tim Berners-Lee Internet Pioneers: Marc Andreessen Wikipedia entry on Programming Languages Webopedia entry on Programming Languages Python Official Website

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