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This Week ...This Week ...
• QBasic For LoopsQBasic For Loops
• Computer HistoryComputer History 11stst – 3 – 3rdrd Generation computers Generation computers
• Website Project is Due!Website Project is Due!
QBasic QBasic For LoopsFor Loops
Looping a variable through a rangeLooping a variable through a range
For For StatementStatement
• LoopsLoops a block of statements a block of statements the block is executed numerous timesthe block is executed numerous times this allows you to create repetitionthis allows you to create repetition
• When do you use it?When do you use it? execute a block a number of timesexecute a block a number of times process data using the set of numbersprocess data using the set of numbers
• VeryVery versatile in QBasic Lite versatile in QBasic Lite
For For StatementStatement
• Uses a numeric variableUses a numeric variable starts with an initial valuestarts with an initial value changes its value for each loopchanges its value for each loop stops once its value is greater than end value stops once its value is greater than end value
• Semantics ...Semantics ... assigns the initial/next value to the variableassigns the initial/next value to the variable executes the block if the variable is not greater executes the block if the variable is not greater
than the end valuethan the end value repeats the processrepeats the process
Default: increment by one (+ 1) in each loop automatically
FOR Quiz = 1 to 3
INPUT "Score: ", Score
LET Sum = Sum + Score
NEXT
PRINT "Average is"; Sum / 3
AverageAverageExampleExample
Inner LoopsInner Loops
• Like all QBasic blocks, you can Like all QBasic blocks, you can put loops within loopsput loops within loops
• The loop in the inner-most block The loop in the inner-most block is an is an inner loopinner loop
• The loop in the outer-most The loop in the outer-most block is an block is an outer loopouter loop
FOR x = 10 to 11
PRINT "Outer: "; x
FOR y = 1 to 2
PRINT " Inner: "; y
NEXT
NEXT
Inner LoopInner LoopExampleExample
Outer: 10
Inner: 1
Inner: 2
Outer: 11
Inner: 1
Inner: 2
Inner LoopInner LoopExample OutputExample Output
Not-So-Simple LoopNot-So-Simple LoopWhy?Why?
• The The For ... NextFor ... Next Statement Statement starts at the first valuestarts at the first value continues continues untiluntil the value of the variable the value of the variable is greater is greater
thanthan the end value the end value• If the start value is greater than the end If the start value is greater than the end
value, the loop value, the loop nevernever executesexecutes
The The StepStep Clause Clause
• Normally, the Normally, the For ... NextFor ... Next Statement Statement increments using increments using +1+1
• The Step Clause allows you to change the The Step Clause allows you to change the increment valueincrement value
• This allows you to:This allows you to: create negative loopscreate negative loops create loops that jump by a specific valuecreate loops that jump by a specific value
FOR var = start TO end STEP inc
Statements
NEXT
Full Full For ... NextFor ... Next Statement SyntaxStatement Syntax The increment is
defined by the step here
FOR x = 1 TO 10 STEP 2
PRINT x
NEXT
Large StepLarge StepExampleExample The increment for
variable x in each loop is 2 here
FOR x = 5 TO 1 STEP -1
PRINT x, x ^ 2
NEXT
Negative StepNegative StepExampleExample
The increment for variable x in each loop is 1 here
While Loop vs. While Loop vs. For LoopFor Loop
• For LoopFor Loop is a form of the is a form of the While LoopWhile Loop• As a result:As a result:
a a While Loop While Loop can implement any can implement any For LoopFor Loop the the For LoopFor Loop is used as a shortcut notation is used as a shortcut notation
x = 1
DO WHILE x <= 5
PRINT x LET x = x + 1 LOOP
While Loop vs. While Loop vs. For LoopFor Loop
FOR x = 1 TO 5
PRINT xNEXT
Lab: 99 Bottles of Lab: 99 Bottles of SomethingSomething
• Overview:Overview: You will use QBasic to print the 99 You will use QBasic to print the 99
Bottles of Beer (Water) SongBottles of Beer (Water) Song Use another drink, water or juice Use another drink, water or juice
• Objectives:Objectives: Use a For Statement to print the songUse a For Statement to print the song Use an If Statement inside the loopUse an If Statement inside the loop
Remember ...Remember ...
• Turn your program Turn your program && your output your output to Lab10 in SacCTto Lab10 in SacCT
• You must do your own workYou must do your own work• If you do not turn in your program, If you do not turn in your program,
you will you will notnot get credit! get credit!
Punched CardsPunched Cards
• Invented by Invented by Joseph-Marie JacquardJoseph-Marie Jacquard
• Textile industryTextile industry control the flow of yarn in a loomcontrol the flow of yarn in a loom used to create patternsused to create patterns
• Adapted to Adapted to automatic pianosautomatic pianos computer datacomputer data
Charles BabbageCharles Babbage
• Known as theKnown as the“Father of Computers”“Father of Computers”
• Created several Created several calculatorscalculators
• Developed the first Developed the first computercomputer
The Difference EngineThe Difference Engine
• In the 1800’sIn the 1800’s log and trig tables were calculated manuallylog and trig tables were calculated manually Babbage knew machines could compute theseBabbage knew machines could compute these
• He designed the He designed the Difference EngineDifference Engine could compute logarithmic and trigonometric datacould compute logarithmic and trigonometric data first machine to be first machine to be automatic in actionautomatic in action it was not finished in his lifetimeit was not finished in his lifetime
The Difference Engine:The Difference Engine:continuedcontinued
• It was completed in March 2008 at the Science It was completed in March 2008 at the Science Museum, London 150 years after its original Museum, London 150 years after its original design, and is faithful to Babbage’s original design, and is faithful to Babbage’s original design (1847-49).design (1847-49).
• It is one of only two Babbage engines consisting It is one of only two Babbage engines consisting of 8,000 parts in bronze, cast iron and steel.of 8,000 parts in bronze, cast iron and steel.
• It weighs five tons and measures 11 feet long and It weighs five tons and measures 11 feet long and 7 feet tall. 7 feet tall.
The Analytical EngineThe Analytical Engine
• A A general-purpose general-purpose calculating machinecalculating machine• He began work in He began work in 18341834
he never finished ithe never finished it it has it has nevernever been built been built
• If built, it would have been one of theIf built, it would have been one of theWonders of the WorldWonders of the World
The Analytical EngineThe Analytical Engine
• Use punched cards to run calculationsUse punched cards to run calculations• Had all the attributes of a modern computerHad all the attributes of a modern computer
Programs – looping, branching – Programs – looping, branching – "Barrels""Barrels" Memory – Memory – "The Store""The Store" Arithmetic Logic Unit – Arithmetic Logic Unit – "The Mill""The Mill" Bus – Bus – "The Rack""The Rack"
Ada LovelaceAda Lovelace
• MathematicianMathematician• Spoke several languagesSpoke several languages• University of Turin lecturerUniversity of Turin lecturer
During a nine-month period in 1842–43, Lovelace During a nine-month period in 1842–43, Lovelace translated Italian mathematician Luigi Menabrea's translated Italian mathematician Luigi Menabrea's memoir (to English) on Babbage's Analytical Engine. memoir (to English) on Babbage's Analytical Engine. With the article, she appended a set of notes that With the article, she appended a set of notes that included a method for calculating a sequence of included a method for calculating a sequence of Bernoulli numbers with the Engine.Bernoulli numbers with the Engine.
Her method is recognized as the worldHer method is recognized as the world’’s first computer s first computer program.program.
Ada LovelaceAda Lovelace
• She made She made extensiveextensive notes notes several volumes, in factseveral volumes, in fact designed several programsdesigned several programs this included how to calculate this included how to calculate
Bernoulli numbers Bernoulli numbers • World's first programmerWorld's first programmer
Census CrisisCensus Crisis
• The The United States Federal ConstitutionUnited States Federal Constitution population must be calculated - censuspopulation must be calculated - census this must be done every 10 yearsthis must be done every 10 years used in the House of Representativesused in the House of Representatives
• However, the U.S. populationHowever, the U.S. population had grown extremely large had grown extremely large the people could the people could notnot be counted in 10 years be counted in 10 years
Herman HollerithHerman Hollerith
• Developed:Developed: first automatic card-feed first automatic card-feed
mechanismmechanism enhanced card readingenhanced card reading the first key punch – 200 to the first key punch – 200 to
300 cards per hour300 cards per hour• Used Used electricityelectricity
Herman HollerithHerman Hollerith
• His systemHis system was used for was used for 18901890 census census only took 9 months!only took 9 months!
• Hollerith foundedHollerith founded Tabulating Machine CompanyTabulating Machine Company it later became it later became International International
Business MachinesBusiness Machines
Alan TuringAlan Turing
• Mathematician, logician & Mathematician, logician & cryptographercryptographer
• "Father of Computer Science""Father of Computer Science" Highest award in Computer Highest award in Computer
Science is the Science is the Turing AwardTuring Award Developed Turing MachinesDeveloped Turing Machines
Alan Turing'sAlan Turing'sMajor WorksMajor Works
• Developed Turing MachinesDeveloped Turing Machines invented in invented in 19371937 logical model – not an actual logical model – not an actual
computercomputer proved programmingproved programming
• Turing TestTuring Test artificial Intelligenceartificial Intelligence no computer has yet passed itno computer has yet passed it
Computer Computer GenerationsGenerations
• Computers are historically classified by Computers are historically classified by their their generationgeneration
• Each generation ...Each generation ... marks a new, major, technologymarks a new, major, technology changes how computers are built and/or usedchanges how computers are built and/or used their are currently their are currently fourfour generations generations
First Generation First Generation ComputersComputers
• 1946 to 19581946 to 1958• Used the Used the vacuum tubevacuum tube
they consumed a lot of powerthey consumed a lot of power they also tended to burn out quicklythey also tended to burn out quickly
• Programs written in machine languagePrograms written in machine language• Data Data
read with Punched Cardsread with Punched Cards stored with Magnetic Tapestored with Magnetic Tape
Atanasoff-Berry Atanasoff-Berry ComputerComputer
• First electronic digital computerFirst electronic digital computer• DevelopmentDevelopment
John Atanasoff John Atanasoff && Clifford Berry Clifford Berry Iowa State UniversityIowa State University built from built from 1937 to 19421937 to 1942
• Speed: 60 HzSpeed: 60 Hz
Atanasoff-Berry Atanasoff-Berry ComputerComputer
• Features:Features: binary digits to represent all databinary digits to represent all data calculations using electronicscalculations using electronics memory is separate from CPUmemory is separate from CPU
• Rebuilt in Rebuilt in 19971997 cost of $350,000cost of $350,000 it worked!it worked!
ENIACENIAC
• EElectronic lectronic NNumerical umerical IIntegrator ntegrator AAnd nd CComputeromputer
• DevelopmentDevelopment John Eckert and John W. Mauchly John Eckert and John W. Mauchly U.S. Ballistics Research Laboratory U.S. Ballistics Research Laboratory Needed to fight World War II – then Cold WarNeeded to fight World War II – then Cold War Compute ballistic firing tablesCompute ballistic firing tables
ENIACENIAC
• Designed to be Designed to be Turing CompleteTuring Complete• Operational in February Operational in February 19461946• FeaturesFeatures
5 KHz (5000 Hz)5 KHz (5000 Hz) programmed by rewiring – programmed by rewiring – pre 1948pre 1948 based on decimal – not binarybased on decimal – not binary weighed 30 tons,18 feet high, 80 feet longweighed 30 tons,18 feet high, 80 feet long
ENIACENIAC
• A tube burned out once every 2 daysA tube burned out once every 2 days• Retired in Retired in 19551955
operational for only operational for only 9 years9 years estimated to have performed more estimated to have performed more
calculations than all of humanity had ever calculations than all of humanity had ever done priordone prior
Grace HopperGrace Hopper
• Admiral in the U.S. NavyAdmiral in the U.S. Navy• Worked on several projectsWorked on several projects
Mark II MainframeMark II Mainframe COBOL Programming LanguageCOBOL Programming Language CompilersCompilers Standardized software testingStandardized software testing
• Discovered the first Discovered the first "bug""bug"
UNIVACUNIVAC
• UnivUniversal ersal AAutomatic utomatic CComputeromputer• Released in Released in 19511951• First commercial computerFirst commercial computer
43 were sold to government and industry43 were sold to government and industry used to tabulate the censusused to tabulate the census
UNIVACUNIVAC
• Some featuresSome features ran programs on punched cardsran programs on punched cards secondary storage: metal oxide tapesecondary storage: metal oxide tape clock: clock: 2.25 MHz2.25 MHz
• Predicted the 1952 electionPredicted the 1952 election Eisenhower over StevensonEisenhower over Stevenson news agencies held the results - news agencies held the results - great publicitygreat publicity
IBM RAMAC 305IBM RAMAC 305
• RRandom andom AAccess ccess MMethod of ethod of AAccounting ccounting and and CControlontrol
• Released in Released in 19561956• First computer to use a hard driveFirst computer to use a hard drive
based on record technologybased on record technology could store 5 million 7-bit characterscould store 5 million 7-bit characters
Second Generation Second Generation ComputersComputers
• 1959 to 19641959 to 1964• Used Used TransistorsTransistors
more reliable than vacuum tubesmore reliable than vacuum tubes required less powerrequired less power
• Compilers were developedCompilers were developed• Disk Storage was developedDisk Storage was developed
DEC DEC PDP-1PDP-1
• PProgrammed rogrammed DData ata PProcessor-rocessor-11• Digital Equipment Corporation (DEC)Digital Equipment Corporation (DEC)• Released Released 19601960• FeaturesFeatures
read data from taperead data from tape used a cathode ray tube (T.V.) to display dataused a cathode ray tube (T.V.) to display data
• The first hacker computerThe first hacker computer• World's first digital video game: Space WarWorld's first digital video game: Space War
Third Generation Third Generation ComputersComputers
• 1965 to 19701965 to 1970• Used integrated circuitsUsed integrated circuits
increased speedincreased speed smaller sizesmaller size lower costlower cost even less electricityeven less electricity
• Birth of the minicomputerBirth of the minicomputer
IBM 360IBM 360
• Most expensive computer project everMost expensive computer project ever the "5 billion dollar gamble"the "5 billion dollar gamble" this is over 30 billion by today's dollarsthis is over 30 billion by today's dollars
• Released Released 19641964• BreakthroughBreakthrough
architecture and implementation are differentarchitecture and implementation are different microcode technologymicrocode technology
IBM 360IBM 360
• It was the It was the firstfirst platform computer platform computer allall 360 computers would be compatible 360 computers would be compatible initial models: 30, 40, 50, 60, 62, and 70 initial models: 30, 40, 50, 60, 62, and 70 peripherals could be interchangedperipherals could be interchanged
• Huge successHuge success companies could buy the best modelcompanies could buy the best model companies could upgrade their systems latercompanies could upgrade their systems later
DEC PDP-8DEC PDP-8
• First successful commercial First successful commercial minicomputerminicomputer released in released in 19651965 it cost less than $20,000it cost less than $20,000
• FeaturesFeatures up to 32k of RAMup to 32k of RAM 1 MHz – varied by model1 MHz – varied by model multiple versions availablemultiple versions available