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Algorithm development

Algorithm development. The invention of the computer. Programming language developments: Machine code Assembler easier to write, debug, and update High level languages strive to be machine independent easier to learn and use 1954 – FORTRAN 1961 – COBOL then ALGOL, LISP, BASIC

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Algorithm development

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  1. Algorithm development

  2. The invention of the computer • Programming language developments: • Machine code • Assembler • easier to write, debug, and update • High level languages • strive to be machine independent • easier to learn and use • 1954 – FORTRAN • 1961 – COBOL • then ALGOL, LISP, BASIC • 1970 – Pascal • 1980’s – C • 1990’s – C++, Java (originally called ?) • and many, many others

  3. High level langauges (HLL) • Not directly understood by the computer • Humanly readable • Requires the user of a compiler • Compiler = program • Input = code written in a HLL • Output = machine code

  4. Pascal (an HLL) • 1970’s • Support for “structured programming” • Control constructs • Linear sequence of commands/instructions • Repetition • Selection • Top-down programming • Problem is broken down into a series of smaller problems which are solved. • Divide-and-conquer technique.

  5. Types of software • OS (operating system) • Programming environment/tools • Applications

  6. Operating Systems (OS) • Windows • Linux • Android (linux-based) • Unix • Mac OS • many others

  7. Programming environments/tools • Tools • emacs (an editor – not a word processor) • vi • g++ • gdb

  8. Programming environments/tools • IDE’s (Integrated Development Environment) • consist of: editor, compiler or interpreter, debugger, linker • examples: jGrasp, netbeans, Eclipse, Ready, Visual C++, Visual BASIC, JBuilder, and many others

  9. Applications • Computer games • Word processors • Graphics packages • Virtual reality software • Web browsers • Presentation • Database • Spreadsheet • And many others.

  10. Social issues • Privacy/anonymity • Quality of information

  11. Program development • Our programming language is Java. • The IDE we will use is jGrasp. • Editor is used to type in program text (it is not a word processor; don’t use a word processor). • Compiler (syntax errors) • Run/execute (semantic errors)

  12. Program development • Java is an object-oriented language. • (Note: Case sensitive.) • Method • named operation • constructor (ctor) • special method w/ same name as class • performs initialization • class may have more than 1 ctor • Class • named group of related methods

  13. Recall “What is a computer?” INPUT (information) PROCESSING OUTPUT (information) MEMORY

  14. Definitions (from http://mathworld.wolfram.com/Algorithm.html) • An algorithm is a specific set of instructions for carrying out a procedure or solving a problem, usually with the requirement that the procedure terminate at some point.

  15. Definitions (from http://mathworld.wolfram.com/Algorithm.html) • Specific algorithms sometimes also go by the names: • method • procedure • routine • subroutine • technique

  16. Definitions (from http://mathworld.wolfram.com/Algorithm.html) The word “algorithm” is a distortion of al-Khwārizmī, a Persian mathematician who wrote an influential treatise about algebraic methods.

  17. Definitions (from http://mathworld.wolfram.com/Algorithm.html) The process of applying an algorithm to an input to obtain an output is called a computation.

  18. Recall “What is a computer?” • How can a Java program perform output? INPUT (information) PROCESSING OUTPUT (information) MEMORY

  19. How can a program perform output? System.out.println( "hello world" );

  20. blocks { System.out.println( "Welcome!" ); System.out.println( "Enjoy the show." ); }

  21. Method/function/procedure public static void main ( String param[] ) { System.out.println( "hi there" ); }

  22. Defining our own objects class MyFirstClass { public static void main ( String param[] ) { System.out.println( "hi there" ); } }

  23. Recall “What is a computer?” • How can a Java program perform input? INPUT (information) PROCESSING OUTPUT (information) MEMORY

  24. How can a Java program perform input? … Scanner s = new Scanner( System.in ); … String str = s.nextLine(); …

  25. We can mix input and output. Scanner s = new Scanner( System.in ); System.out.print( "Enter your name: " ); String name = s.nextLine(); System.out.println( "Thanks." ); s.close();

  26. Complete program that does both input & output. import java.util.Scanner; class MySecondClass { public static void main ( String param[] ) { Scanner s = new Scanner( System.in ); System.out.print( "Enter your name: " ); String name = s.nextLine(); System.out.println( "Thanks." ); s.close(); } }

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