# CMSC 120: Visualizing Information 1/29/08 Introduction to Computing.

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CMSC 120: Visualizing Information 1/29/08 Introduction to Computing

What is Computing? To determine by calculating To determine by calculating To use a computer To use a computer What is a Computer? A device that accepts information (data), A device that accepts information (data), processes it according to specific instructions, processes it according to specific instructions, and provides the results as new information and provides the results as new information

First Computers Abacus 0 1 2 3 4 5 6 7 8 9 Number Systems Pen and Paper People *A computer: a person who works with numbers

Mechanical Age (1450-1840) Pascaline Blaise Pascal (1642) Blaise Pascal (1642) A gear driven adding machine A gear driven adding machine Slide Rule Early 1600s Early 1600s An analog computer An analog computer Analog: represents data by measurement of a continuous physical variable

Mechanical Age (1450-1840) Gottfried Wilhelm von Leibniz (1670s) Gottfried Wilhelm von Leibniz (1670s) Add, subtract, multiply, divide Add, subtract, multiply, divide Mechanically unreliable Mechanically unreliable Stepped Reckoner

Mechanical Age (1450-1840) Punch Card Joseph Jacquard (1810) Joseph Jacquard (1810) Weaving instructions for looms stored in cards with holes punched in them Weaving instructions for looms stored in cards with holes punched in them

Mechanical Age (1450-1840) The Difference Engine (1822) The Analytical Engine Charles Babbage Charles Babbage Followed program in punched cards Followed program in punched cards Store information in memory unit Store information in memory unit Make decisions Make decisions

Analytical Engine Anecdote Babbage’s collaborator was Ada, Countess of Lovelace, daughter of Lord Bryon Babbage’s collaborator was Ada, Countess of Lovelace, daughter of Lord Bryon Sponsored, tested, publicized device Sponsored, tested, publicized device “First Programmer” “First Programmer” Stated that the engine would never “originate anything” Stated that the engine would never “originate anything” –A machine, no matter how powerful, could think

Electro-mechanical Age (1840 – 1940) Hermann Hollerith (end 19 th century) Hermann Hollerith (end 19 th century) Created to tabulate US Census Created to tabulate US Census Used electricity Used electricity Information punched into cards Information punched into cards Metal pins open and closed electrical circuits Metal pins open and closed electrical circuits Electronic Tabulating Machine Population: 63 million; 6 weeks Population: 63 million; 6 weeks Founding product of International Business Machines (IBM) Founding product of International Business Machines (IBM)

Electro-mechanical Age (1840 – 1940) IBM + Harvard under leadership of Howard Aiken (1930s) IBM + Harvard under leadership of Howard Aiken (1930s) Storage: Mechanical relay telephone switches Storage: Mechanical relay telephone switches Input: Punch Cards Input: Punch Cards Output Output No decision making No decision making Mark I 51 feet in length 5 tons 750, 000 parts What is the difference between a calculator and a computer?

The First Computer Bug Grace Hopper (1909 – 1992) Grace Hopper (1909 – 1992) One of first programmers of Mark I One of first programmers of Mark I Developed first compiler Developed first compiler

Electronic Age (1840 – Today) Electronic Numerical Integration and Calculator (ENIAC) John Mauchly and J. Presper Eckert (finished 1946) John Mauchly and J. Presper Eckert (finished 1946) Initially secret military project begun during WWII Initially secret military project begun during WWII University of Pennsylvania University of Pennsylvania

Electronic Age (1840 – Today) Occupied 1500 square feet Occupied 1500 square feet Weighed 30 tons Weighed 30 tons Used vacuum tubes Used vacuum tubes –>17,000 Able to make decisions: first true computer Able to make decisions: first true computer Programming involved wiring and switch flipping Programming involved wiring and switch flipping ENIAC

Electronic Age (1840 – Today) John von Neumann (1940s) John von Neumann (1940s) Storing computer instructions in a central processing unit (CPU) Storing computer instructions in a central processing unit (CPU) –No longer necessary to flip switches or rewire Large Corporations, US Government Large Corporations, US Government Stored Program Computer Processing Model: Processing Model: –Input data –Store data while being processed –Process data according to specific instructions –Output the results in the form of new data

Electronic Innovations Vacuum tubes Vacuum tubes –Large and expensive –UNIVAC: 35 tons –1000 calculations per second Transistor: semiconductor used as an amplifier or electronically controlled switch Transistor: semiconductor used as an amplifier or electronically controlled switch –Reduced size –10,000 claculations per second –IBM model 650 (1960s) –Magnetic tape replaced punched cards

Electronic Innovations Integrated Circuits Integrated Circuits –Replacement of transistors with integrated circuits or chips –Silicon blocks with logic circuits etched onto surface –Millions of calculations per second –IBM System 360 was one of the first computers to use integrative circuits –Hospitals and Universities could now own computers

Modern Computers 1951 – 1958: Vacuum tubes (First Generation) 1951 – 1958: Vacuum tubes (First Generation) 1959 – 1964: Transistors (Second Gen) 1959 – 1964: Transistors (Second Gen) 1965 – 1970: Integrated Circuits (Third Gen) 1965 – 1970: Integrated Circuits (Third Gen) 1970 + : Large Scale Chips and Microprocessors (Fourth Gen) 1970 + : Large Scale Chips and Microprocessors (Fourth Gen)

Modern Computers Microprocessor: a CPU an a single chip Microprocessor: a CPU an a single chip –Designed in 1970 by Marcian Hoff (Intel Corporation) Microcomputer: a desktop size computer Microcomputer: a desktop size computer –ALTAIR (1975) –Apple (Stephen Wozniak and Steven Jobs; 1977)

The State of Modern Computing Computing power doubles every 18-24 months Computing power doubles every 18-24 months From the BBC

Hardware (Computer Architecture) Input Devices Input Devices Memory Memory Central Processing Unit Central Processing Unit Output Devices Output Devices InputMemoryOutput CPU

Memory Read Only Memory (ROM) Read Only Memory (ROM) –Most basic operating instructions –Permanent Random Access Memory (RAM) Random Access Memory (RAM) –Main memory –Data and instructions are temporarily stored Registers Registers –Temporary memory locations within the CPU Auxiliary Memory Auxiliary Memory

CPU Directs all activities of the computer Directs all activities of the computer All information flows through the CPU All information flows through the CPU “Brain” “Brain” –Only executes tasks according to instructions it has been given Arithmetic Logic Unit (ALU) Arithmetic Logic Unit (ALU) –Adds –Compares

Software Computer programs Computer programs Interface between computer and user Interface between computer and user –Disk Operating System (DOS) –MS-DOS, Windows, Linux, UNIX Graphical User Interface (GUI) Graphical User Interface (GUI)