Introduction What is a Computer? Programming a Computer

Introduction What is a Computer? Programming a Computer
Types of Computer Systems History of Computers The Software Crisis Programming Languages

A computer is an information-processing machine
What is a Computer? Computer is a machine Has parts Runs on electricity Breaks down sometimes What makes it different from other machines? Can follow a list of instructions Instructions process symbols A computer is an information-processing machine Therefore Programming and Problem Solving with Java

What is a Computer? Computer follows a list of instructions one instruction at a time Start with first instruction Do each next instruction in turn Stop when last instruction reached Similar to how you follow a list of instructions... Programming and Problem Solving with Java

What is a Computer? Example of following instructions - assemble a bike Right Pedal 1. Find the pedal with an "R" marked on the end of the threads. 2. Insert the threads into the opening on the crank on the right side of the bicycle. 3. Twist the threads into the crank by hand in a clockwise direction. 4. Tighten the threads securely with a 5/8-inch open-end wrench. Left Pedal Follow the same assembly instructions for the right pedal (above) but twist the threads in a counterclockwise direction. Programming and Problem Solving with Java

What is a Computer? Kinds of instructions a computer can follow (in one step) “Add the numbers 16 and 23” Kinds of instructions a computer can’t follow (in one step) “Balance my checkbook” What’s the difference? Computer instructions are simple (add 2 numbers, subtract one number from another) Must combine thousands of computer instructions in a program to do more complex tasks Programming and Problem Solving with Java

What is a Computer? Kinds of computer instructions
Arithmetic: add, subtract, multiply, divide Comparison: compare two numbers to see which is greater, or whether the two numbers are equal or not Branching: jump to some other instruction in the program (list of instructions) and continue processing from there A computer can execute millions of these simple instructions each second Programming and Problem Solving with Java

What is a Computer? Major parts of a computer
Programming and Problem Solving with Java

What is a Computer? A vending machine is like a computer

What is a Computer? Common input and output devices

What is a Computer? Central Processing Unit (CPU)
Most important part of the computer Follows instructions Important characteristics Clock speed How fast the computer switches between 2 on states or 2 off states Early 80’s: 5,000,000 times per second (5 MHz) Today: 400,000,000 to 1,000,000,000 and up! (400 MHz to 1 GHz) Instruction set The set of machine language instructions the CPU understands Examples: Intel Pentium, Motorola PowerPC, IBM AS/400 Some CPUs understand machine language instructions of others -- AMD and Cyrix chips understand Intel Pentium instructions Programming and Problem Solving with Java

What is a Computer? Subcomponents of a CPU
The arithmetic/logic unit, or ALU: does addition, subtraction, and other arithmetic operations, and also compares values The control unit. determines which instruction to execute next A small number of registers. each is a high-speed storage area for temporary results Programming and Problem Solving with Java

What is a Computer? Types of Computer Memory Primary Memory Primary
Secondary Primary Memory Connected directly to the CPU Usually called RAM (random-access memory) Usually loses contents when power switched off -- volatile Programming and Problem Solving with Java

What is a Computer? Secondary Memory Disks, tapes, floppy disks
Is sometimes removable Much cheaper than primary memory Slower than primary memory Keeps contents when power switched off -- non-volatile Programming and Problem Solving with Java

What is a Computer? Types of Computer Memory

What is a Computer? Primary Memory Can imagine as sequence of cells
Each cell has a memory address First cell is memory address 0 Programming and Problem Solving with Java

What is a Computer? Primary Memory
Each memory cell stores a single value, such as a small number If you put a new value into a memory cell, the old contents is lost Programming and Problem Solving with Java

What is a Computer? Primary Memory
Can retrieve the contents of a cell without losing the contents Programming and Problem Solving with Java

What is a Computer? Secondary Memory Information clustered in files
File: collection of related information Each file has a name Example: NAMES.DAT, Balance.java Programming and Problem Solving with Java

Programming a Computer
How we solve most problems without a computer Analyze the problem, come up with a solution Programming and Problem Solving with Java

How we can get the computer to solve a problem Must come up with an algorithm (series of steps) Computer follows the steps to solve the problem Programming and Problem Solving with Java

Algorithm Steps that a computer can follow to solve a problem Holiday Cookies 1 cup sugar 1/4 tsp. ginger 3/4 cup shortening 1 tsp. cinnamon 1 cup dark corn syrup 1/2 tsp. nutmeg 2 eggs 1/2 tsp. cloves 1 lemon rind (grated) 2 tsp. anise seed 3 cups flour 3/4 tsp. ground cardaman 1 tsp. baking powder icing (powder sugar and water) 1 tsp. baking soda colored sugar and candy decorations 1. Sift dry ingredients together in a large bowl and set aside. 2. In another large bowl, use mixer to cream sugar and shortening together. 3. Mix syrup, eggs, and lemon rind into sugar and shortening mixture. 4. Add dry ingredients to mixture gradually. 5. Refrigerate at least one hour to make handling easier. 6. With rolling pin, roll out to 1/8-inch thickness on a floured surface, and cut with cookie cutters. 7. Bake on greased cookie sheet minutes at 375°F. 8. Remove from cookie sheet and let cool to room temperature. 9. Frost with icing, and decorate with colored sugar and candy. Similar to a recipe Programming and Problem Solving with Java

Recipe lists steps, but doesn’t say who is doing the steps Implied that you (the cook) should do the steps Many algorithms written this way -- structured approach to programming New approach -- object-oriented programming Consists of a set of cooperating objects trying to accomplish a goal Each step says who (which object) should do that step Similar to the script for a play Programming and Problem Solving with Java

THE IMPORTANCE OF BEING EARNEST by Oscar Wilde The Persons of the Play John Worthing, J.P. Lady Bracknell Algernon Moncrieff Hon. Gwendolen Fairfax Rev. Canon Chasuble, D.D. Cecily Cardew Merriman, Butler Miss Prism, Governess Lane, Manservant The Scenes of the Play Act I: Algernon Moncrieff's Flat in Half-Moon Street, W. Act II: The Garden at the Manor House, Woolton. Act III: Drawing-Room at the Manor House, Woolton Programming and Problem Solving with Java

THE IMPORTANCE OF BEING EARNEST (continued) ACT ONE SCENE. Morning-room in Algernon's flat in Half-Moon Street. The room is luxuriously and artistically furnished. The sound of a piano is heard in the adjoining room. (Lane is arranging afternoon tea on the table, and after the music has ceased, Algernon enters.) ALGERNON. Did you hear what I was playing, Lane? LANE. I didn't think it polite to listen, sir. ALGERNON. I'm sorry for that, for your sake. I don't play accurately-anyone can play accurately-but I play with wonderful expression. As far as the piano is concerned, sentiment is my forte. I keep science for life. LANE. Yes, sir. ALGERNON. And, speaking of the science of life, have you got the cucumber sandwiches cut for Lady Bracknell? LANE. Yes, sir. (Hands them on a salver.) ALGERNON. (Inspects them, takes two, and sits down on the sofa.) Oh! ... by the way, Lane, I see from your book that on Thursday night, when Lord Shoreman and Mr. Worthing were dining with me, eight bottles of champagne are entered as having been consumed. LANE. Yes, sir; eight bottles and a pint. ALGERNON. Why is it that at a bachelor's establishment the servants invariably drink the champagne? I ask merely for information. Programming and Problem Solving with Java

THE IMPORTANCE OF BEING EARNEST (continued) LANE. I attribute it to the superior quality of the wine, sir. I have often observed that in married households the champagne is rarely of a first-rate brand. ALGERNON. Good Heavens! Is marriage so demoralizing as that? LANE. I believe it is a very unpleasant state, sir. I have had very little experience of it myself up to the present. I have only been married once. That was in consequence of a misunderstanding between myself and a young person. ALGERNON. (Languidly.) I don't know that I am much interested in your family life, Lane. LANE. No, sir; it is not a very interesting subject. I never think of it myself. ALGERNON. Very natural, I am sure. That will do, Lane, thank you. LANE. Thank you, sir. (Lane goes out.) ALGERNON. Lane's views on marriage seem somewhat lax. Really, if the lower orders don't set us a good example, what on earth is the use of them? They seem, as a class, to have absolutely no sense of moral responsibility. (Enter Lane.) LANE. Mr. Ernest Worthing. (Enter Jack. Lane goes out.) ... Programming and Problem Solving with Java

Why is an object-oriented algorithm like a script? Object-oriented algorithm simulates activities of several explicit actors Each actor has specific steps to perform Each actor free to use any appropriate technique to accomplish its task Combined effort of all these simulated actors results in the goal of the algorithm Combined effort of real actors of a play results in enjoyable entertainment Programming and Problem Solving with Java

Programming languages Very formal language with strict rules about spelling and grammar Need write algorithm in a programming language before running the algorithm on the computer Many programming languages Will use Java in this course Programming and Problem Solving with Java

Computers understand machine language directly Example: add 16 and 23 in Intel 8086 machine language Programming and Problem Solving with Java

Parts of machine language program step First statement from example Instruction says: Copy the number 16 into the AL register Difficult to read and write machine language! Copy information to a register Use the AL register The number 16 in binary (base 2) Programming and Problem Solving with Java

Assembly language One step up from machine language Each assembly language instruction corresponds to one machine language instruction MOV AL,16D ADD AL,23D MOV [SUM],AL Programming and Problem Solving with Java

Assembly language Computer can’t understand assembly language directly Must translate from assembly to machine language Assembler: program that does this translation Programming and Problem Solving with Java

High-level languages Each high-level language instruction may correspond to several machine language instructions Easier for people to read and write than assembly Java example: (Note: Java usually translated to Java bytecodes, not Intel machine language...) sum = ; Programming and Problem Solving with Java

High-level languages Must translate high-level language program to machine language before computer can execute it Compiler: program that does this translation Programming and Problem Solving with Java

Programming a Computer: Java
The Java Programming Language A high-level language Java compiler translates to Java bytecodes for execution on a Java Virtual Machine (JVM) Programming and Problem Solving with Java

Advantage of Java Virtual Machine approach Can run compiled Java program on any machine with a Java Virtual Machine installed Makes compiled Java programs very portable Disadvantage Takes more time -- Java programs run slower than programs compiled to machine code BUT ... Today’s machines are so fast that the difference is not noticeable for many programs Programming and Problem Solving with Java

Kinds of Java programs Applications Applets Run as stand-alone programs Programs stored on the same machine they run on Like a text editor, word processor, spreadsheet, ... Can be graphical or console-based Run inside a web browser Programs stored on a web server, run on a client machine Programming and Problem Solving with Java

Example Java program (application) // This Java program finds the sum of 16 and 23, // then displays the result. public class Add16And23 { public static void main(String[] args) int sum; sum = ; System.out.println("The sum of 16 and 23 is " + sum); } Steps to run this program Type the program text exactly Save the program in file Add16And23.java Compile the program with a Java compiler Run program Add16And23.class with a JVM interpreter Programming and Problem Solving with Java

Use an editor that saves text files, such as MS-DOS edit (in MS-DOS box) Programming and Problem Solving with Java

Compile the program javac Add16And23.java Run the program java Add16And23 Result: program should display The sum of 16 and 23 is 39 $ javac Add16And23.java $ java Add16And23 The sum of 16 and 23 is 39 $ Unix display Programming and Problem Solving with Java

Programming: Development
Example program: display average of series First step: understand the problem Where should program get the numbers? Keyboard How does program know how many numbers? Will enter 0 at end of list Where should program display result? On screen Second step: come up with algorithm Solve problem yourself -- write down steps you took Result is an algorithm Programming and Problem Solving with Java

Steps for finding average of series of numbers Programming and Problem Solving with Java

Convert steps into an algorithm Display the program's title Set running total to 0. Set running count to 0. Repeat these steps: Read a value. Check if value is 0 (stop this loop if so). Add value to running total. Add 1 to running count. Compute the average by dividing the running total by the count. Display the average. Programming and Problem Solving with Java

Convert algorithm into program // This program displays the average of a series of // numbers terminated by zero. The user enters the numbers using // the keyboard, and the average is displayed on the screen. import java.io.*; import java.text.NumberFormat; public class ComputeAverage { public static void main(String[] args) throws java.io.IOException, java.text.ParseException double inputValue; // Last value read from the user double runningTotal; // Total of all input values read so far int runningCount; // Count of all input values read so far double average; // Average of input values // Create an input stream and attach it to the standard // input stream BufferedReader inStream = new BufferedReader(new InputStreamReader(System.in)); // Create a number formatter object NumberFormat formatter = NumberFormat.getInstance(); // Display the program title System.out.println("--- Compute Average ---"); // Set running total to 0 runningTotal = 0; Programming and Problem Solving with Java

// Set running count to 0 runningCount = 0; // Read the first input value System.out.print("Enter a value (0 to stop): "); System.out.flush(); inputValue = formatter.parse(inStream.readLine()).doubleValue(); // Keep reading until 0 while (inputValue != 0) { // Add value to running total runningTotal = runningTotal + inputValue; // Add 1 to running count runningCount = runningCount + 1; // Read the next input value inputValue = formatter.parse(inStream.readLine()).doubleValue(); } // Compute the average average = runningTotal / runningCount; // Display the average System.out.println("The average is " + average); Programming and Problem Solving with Java

Last step: Make sure the program works correctly First test -- ok --- Compute Average --- Enter a value (0 to stop): 9 Enter a value (0 to stop): 3.2 Enter a value (0 to stop): 8 Enter a value (0 to stop): 0 The average is Second test -- ok Enter a value (0 to stop): 9.1 Enter a value (0 to stop): 2.6 Enter a value (0 to stop): 7.3 Enter a value (0 to stop): 1.4 Enter a value (0 to stop): 6.44 Enter a value (0 to stop): 5.72 The average is Third test -- not ok (doesn’t work if nothing to average) The average is NaN Programming and Problem Solving with Java

Modified program // This program displays the average of a series of // numbers terminated by zero. The user enters the numbers using // the keyboard, and the average is displayed on the screen. import java.io.*; import java.text.NumberFormat; public class ComputeAverage { public static void main(String[] args) throws java.io.IOException, java.text.ParseException double inputValue; // Last value read from the user double runningTotal; // Total of all input values read so far int runningCount; // Count of all input values read so far double average; // Average of input values // Create an input stream and attach it to the standard // input stream BufferedReader inStream = new BufferedReader(new InputStreamReader(System.in)); // Create a number formatter object NumberFormat formatter = NumberFormat.getInstance(); // Display the program title System.out.println("--- Compute Average ---"); // Set running total to 0 runningTotal = 0; Programming and Problem Solving with Java

// Set running count to 0 runningCount = 0; // Read the first input value System.out.print("Enter a value (0 to stop): "); System.out.flush(); inputValue = formatter.parse(inStream.readLine()).doubleValue(); // Keep reading until 0 while (inputValue != 0) { // Add value to running total runningTotal = runningTotal + inputValue; // Add 1 to running count runningCount = runningCount + 1; // Read the next input value inputValue = formatter.parse(inStream.readLine()).doubleValue(); } if (runningCount > 0) // Compute the average average = runningTotal / runningCount; // Display the average System.out.println("The average is " + average); else System.out.println("Can't compute average: No input values"); Changes Programming and Problem Solving with Java

Last step: Test program again First test -- ok --- Compute Average --- Enter a value (0 to stop): 9 Enter a value (0 to stop): 3.2 Enter a value (0 to stop): 8 Enter a value (0 to stop): 0 The average is Second test -- ok Enter a value (0 to stop): 9.1 Enter a value (0 to stop): 2.6 Enter a value (0 to stop): 7.3 Enter a value (0 to stop): 1.4 Enter a value (0 to stop): 6.44 Enter a value (0 to stop): 5.72 The average is Third test -- ok Can't compute average: No input values Programming and Problem Solving with Java

Steps in program development Understand the problem Come up with an algorithm Write the program Test the program Programming and Problem Solving with Java

Understand the problem Need to understand problem thoroughly before beginning to write program Tempting to start writing program before understanding problem -- probably single most common cause of errors in programs How to understand the problem Look at input and output requirements Ask people involved with the problem domain Try writing about the program -- write what it should do in your own words Programming and Problem Solving with Java

Come up with an algorithm Algorithm is a series of steps, and it ... is finite -- can’t have infinite series of steps is unambiguous -- must state precisely what to do at each step is effective -- must do what it is supposed to to will terminate -- won’t go on forever Programming and Problem Solving with Java

Write the program If you have an algorithm this step is mechanical Gets easier the more you learn and use Java Desk checking Simulate the action of the computer in your mind Good time to do this is as you write the program (you’re thinking about the program anyway) Programming and Problem Solving with Java

Test the program Try the program with sample data Make sure to try several different samples (may work on one set but not others) Don’t worry if it doesn’t work the first time -- professionals rarely get it right the first time, either Programming and Problem Solving with Java

Types of Computers Four major types of computer systems
Single-user personal computer Time-sharing computer Batch computer Network computer system Programming and Problem Solving with Java

Types of Computers Single-user personal computer
One person uses at a time Has become popular since early 80’s Interactive -- computer responds immediately to user commands Programming and Problem Solving with Java

Types of Computers Time-sharing computer
Many people can use simultaneously Each person uses a terminal connected to the computer Programming and Problem Solving with Java

Types of Computers How does time-sharing computer service many people simultaneously? Only appears to act this way Actually does a little bit of work for each person in turn Process is called polling Polls so fast that it seems like the computer is serving everyone at the same time Programming and Problem Solving with Java

Types of Computers Batch computer system
Not interactive -- must schedule work with computer operator Operator schedules work so the computer can get the most work done in the shortest time Advantage of batch: efficiency Used in large companies for repetitive tasks Payroll, accounting, ... Programming and Problem Solving with Java

Types of Computers Computer network
Group of connected computers Server: fast, expensive computer that stores programs and other files for the other computers (clients) Advantage of network vs. time-sharing Each client is a computer Response time is better Programming and Problem Solving with Java

History of Computers Abacus: oldest mechanical calculating aid
Invented in Babylon about 3000 years ago Also used by Chinese Each wire represents a decimal position (ones, tens, ...) Can do addition, subtraction, multiplication and division by moving beads on the strings Programming and Problem Solving with Java

History of Computers Blaise Pascal Gottfried von Leibnitz
Invented first mechanical calculator in 1642 Did multiplication and division Gottfried von Leibnitz Expanded Pascal's machine in 1671 Handled multiplication, division, and square roots Joseph-Marie Jacquard Invented loom that read tape of punched cards in 1801 Wove cloth according to instructions on cards First machine that could be reprogrammed Programming and Problem Solving with Java

History of Computers Charles Babbage
Designed Difference Engine (mid 1800’s) Supposed to compute and print mathematical tables Never completed -- Babbage spent time designing Analytical Engine Designed to follow instructions in a program and thus handle any computation Would store program on cards in the machine's memory -- this is the stored program concept Never completed -- English government stopped the funding Probably wouldn’t have worked -- required metalworking skills beyond what was possible at the time Programming and Problem Solving with Java

History of Computers Augusta Ada (later Countess of Lovelace)
World’s first computer programmer Assisted Babbage Translated one of Babbage’s papers on Analytical Engine from French to English (1842) In margins, she wrote examples of how to use the machine -- program examples Programming and Problem Solving with Java

History of Computers Herman Hollerith
Invented method of using punched cards for automated data processing US government used Hollerith's machines to tabulate the 1890 census Hollerith's firm later merged with three other firms to become International Business Machines (IBM) Punched cards used for tabulating and sorting information into the 1960's Programming and Problem Solving with Java

History of Computers Howard Aiken
Designed the Mark I computer -- the world's first automatic computer (1944) Operated with electro-mechanical switches Able to multiply two numbers together in six seconds John W. Mauchly and J. Presper Eckert Designed ENIAC -- the first general-purpose electronic computer (1946) Hundreds of times faster than any electro-mechanical computing device Programmed by plugging wires into holes along the outside of the machine. Programming and Problem Solving with Java

History of Computers First generation computers (1950’s)
UNIVAC I (1951, Sperry-Rand): first commercial computer Other companies soon followed Computers were bulky, unreliable Used vacuum tubes for electronic switching (hot -- burned out often) Most programs written in machine language Used punched cards for data storage Programming and Problem Solving with Java

History of Computers Second generation computers (late 50’s - mid 60’s) Started using transistors instead of vacuum tubes Computers became more reliable First high-level languages (FORTRAN, COBOL, Algol) Larger primary memory Magnetic tapes used for long-term data storage Programming and Problem Solving with Java

History of Computers Third generation computers (mid 60’s to early 70’s) IBM introduced System 360 line: every machine in the line could run the same programs Integrated circuits used: contains many transistors Most computers ran in batch mode Programming and Problem Solving with Java

History of Computers Fourth generation computers (early 70’s on)
Very large scale integration: hundreds, thousands, or millions of transistors on a single chip Computers have become inexpensive and reliable Time-sharing popular in 1970’s and 1980’s Today, single-user personal computers are popular The Internet connects many computers in a world-wide computer network Programming and Problem Solving with Java

Software Crisis Hardware vs. software
Hardware: physical parts of the computer Software: computer programs Advances in hardware have been spectacular Fast, affordable computer systems Computers in everyday appliances Advances in software Have been many significant advances (high-level languages, compilers, object-oriented programming, modern design techniques, ...) Still need to do more though... Programming and Problem Solving with Java

Software Crisis The Software Crisis Today, many programs are
Expensive: they cost much more than initial projections Unreliable: they have serious errors which cause them to work incorrectly Late: they are delivered months or years after they're promised This is a crisis ... The Software Crisis Programming and Problem Solving with Java

Software Crisis Abstraction Levels of abstraction
Ignore details, concentrate on essential features Most powerful tool to solve the software crisis Levels of abstraction Sometimes, details at one level become essential features at another level Example: stereo Consumer level: concentrate on tuner, CD player, tape desk, speakers, amplifier Stereo designer: concentrate on circuits, discrete parts, chips Chip designer: concentrate on circuits within the chip Programming and Problem Solving with Java

Software Crisis Use abstraction when writing computer program
Programmer gives a name to each part of the program When working within the part, programmer concentrates on the steps within that part When working outside the part, programmer thinks of the part by its name (ignores the steps within) Usually several levels of abstraction in a computer program Method: most detailed level Class: consists of several methods (and other things...) Package: consists of several classes System of packages: consists of several packages Programming and Problem Solving with Java

Programming Languages
Hundreds of high-level programming languages No best programming language for all uses Some are better than others for certain uses Four major groups Procedural Functional Logic Object-oriented Programming and Problem Solving with Java

Languages: Procedural
Procedural languages Largest group of languages Also called imperative languages Program consists of list of statements Variables Program stores temporary values in variables, and can change the value of a variable Different from mathematics: once we have chosen the value of a variable, it remains fixed throughout the expression Programming and Problem Solving with Java

BASIC (Beginner’s All-purpose Symbolic Instruction Code) Popular language for beginners Simple syntax (originally only 14 statement types) Can run on small computers Example 10 REM THIS BASIC PROGRAM FINDS THE SUM OF 20 REM 16 AND 23, THEN DISPLAYS THE RESULT. 30 LET SUM = 40 PRINT "The sum of 16 and 23 is ", SUM 50 END Microsoft Visual BASIC Much more sophisticated version of BASIC Full-fledged development system for Microsoft Windows Programming and Problem Solving with Java

COBOL (COmmon Business Oriented Language) Most commonly used language in business Designed for ease of data movement Example IDENTIFICATION DIVISION. PROGRAM-ID ADDNUMS. AUTHOR SLACK. DATE-WRITTEN. JUL 11,1997. DATE-COMPILED. JUL 12,1997. * THIS COBOL PROGRAM FINDS THE SUM * OF 16 AND 23, THEN DISPLAYS THE RESULT. ENVIRONMENT DIVISION. CONFIGURATION SECTION. SOURCE-COMPUTER. IBM-370. OBJECT-COMPUTER. IBM-370. DATA DIVISION. WORKING-STORAGE SECTION. 77 TOTAL PICTURE 99. PROCEDURE DIVISION. ADD 16, 23 GIVING TOTAL. DISPLAY 'THE SUM OF 16 AND 23 IS ', TOTAL UPON CONSOLE. STOP RUN. END PROGRAM Programming and Problem Solving with Java

FORTRAN (FORmula TRANslator) The first high-level language Popular with scientists and engineers (although many engineers are switching to C and C++ today) Example PROGRAM ADDNUMS C THIS FORTRAN PROGRAM FINDS THE SUM OF C AND 23, THEN DISPLAYS THE RESULT. INTEGER SUM SUM = WRITE (*, 10) SUM 10 FORMAT ('THE SUM OF 16 AND 23 IS ', I2) STOP END Programming and Problem Solving with Java

Popular with programmers who write system-level code (operating systems, compilers, ...) Example /* This C program finds the sum of 16 and 23, then displays the result. */ #include <stdio.h> void main(void) { int sum; sum = ; printf("The sum of 16 and 23 is %d\n", sum); } Programming and Problem Solving with Java

Pascal (named after Blaise Pascal) Designed as a simple alternative to Algol (another early programming language) Used extensively to teach programming until the early 1990’s Example PROGRAM AddNums (Input, Output); { This Pascal program finds the sum of 16 and 23, then displays the result. } VAR Sum : Integer; BEGIN Sum := ; writeLn ('The sum of 16 and 23 is ', Sum) END. Programming and Problem Solving with Java

Languages: Functional
Functional languages Based on mathematical functions Program consists of functions and function calls No variables in a pure functional language Lisp Most popular functional language Used widely in artificial intelligence (especially in the US) Example ; This Lisp program finds the ; sum of 23 and 16, then displays the result. (progn (let (Sum) (setq Sum ( )) (princ "The sum of 23 and 16 is ") (princ Sum) ) Programming and Problem Solving with Java

Languages: Logic Logic languages
Based on formal rules of logic and inference Once set, program can't change value of a variable Program consists of a set of known facts, plus rules for inferring new facts from the existing facts Programming and Problem Solving with Java

Languages: Logic Prolog Most popular logic language
Used widely in artificial intelligence (especially in Europe and Japan) Example /* This Prolog program finds the sum of 16 and 23, then displays the result. */ run :- Sum is , write ("The sum of 16 and 23 is ", Sum), nl. Programming and Problem Solving with Java

Languages: Logic Another example of Prolog
/* Shows Prolog's inference ability */ likes(tom, pizza). likes(tom, apple). likes(jill, taco). likes(jill, apple). likes(bob, beans). likes(bob, apple). likes(jody, Food) :- likes(jill, Food), likes(bob, Food). Run program by writing a query Example Goal: likes(jill, Food) Food=taco Food=apple 2 Solutions Can also infer solutions based on known facts Goal: likes(jody, Food) 1 Solution Programming and Problem Solving with Java

Languages: Object-oriented
Object-oriented languages Model each real-world entity as an object Each object has set of values and behaviors Each object is therefore active, because it has behaviors Simula (Simulation language) First object-oriented language (1967) Smalltalk First pure object-oriented language (early 1980’s) Everything in the language is an object Programming and Problem Solving with Java

Introduced in the mid 1980’s Based on the C language Hybrid language: procedural & object-oriented Example: // This C++ program finds the sum of 16 and 23, // then displays the result. #include <iostream.h> void main(void) { int sum; sum = ; cout << "The sum of 16 and 23 is " << sum << endl; } Programming and Problem Solving with Java

Java Introduced in 1995 by Sun Microsystems Object-oriented language, but not as pure as Smalltalk In Java, primitive values (numbers, characters) are not objects -- they are values In Smalltalk, everything is an object During its research, was designed for use in appliances Released version designed for use on the Internet and as a general-purpose programming language Probably the most famous programming language of all time Lots of coverage in regular news, unlike other programming languages Huge excitement about the language Programming and Problem Solving with Java

Introduction What is a Computer? Programming a Computer

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