algorithm development. the invention of the computer programming language developments: 1. machine...
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Algorithm development
The invention of the computer
Programming language developments:1. Machine code2. Assembler
easier to write, debug, and update3. 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
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
Pascal (an HLL)
1970’s Support for “structured programming”
Control constructs1. Linear sequence of commands/instructions
2. Repetition
3. Selection
Top-down programming Problem is broken down into a series of smaller
problems which are solved. Divide-and-conquer technique.
Types of software
1. OS (operating system)
2. Programming environment/tools
3. Applications
Operating Systems (OS)
Windows Linux
Android (linux-based) Unix Mac OS many others
Programming environments/tools
Tools emacs (an editor – not a word processor) vi g++ gdb
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
Applications
Computer games Word processors Graphics packages Virtual reality software Web browsers Presentation Database Spreadsheet And many others.
Social issues
Privacy/anonymity
Quality of information
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)
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
Recall “What is a computer?”
INPUT
(information)
PROCESSING OUTPUT
(information)
MEMORY
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.
Definitions (from http://mathworld.wolfram.com/Algorithm.html)
Specific algorithms sometimes also go by the names: method procedure routine subroutine technique
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.
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.
Recall “What is a computer?”
INPUT
(information)
PROCESSING OUTPUT
(information)
MEMORY
How can a Java program perform output?
How can a program perform output?
System.out.println( "hello world" );
blocks
{
System.out.println( "Welcome!" );
System.out.println( "Enjoy the show." );
}
Method/function/procedure
public static void main ( String param[] ) {
System.out.println( "hi there" );
}
Defining our own objects
class MyFirstClass {
public static void main ( String param[] ) {
System.out.println( "hi there" );
}
}
Recall “What is a computer?”
INPUT
(information)
PROCESSING OUTPUT
(information)
MEMORY
How can a Java program perform input?
How can a Java program perform input?
…
Scanner s = new Scanner( System.in );
…
String str = s.nextLine();
…
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();
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();
}
}