Programming

• Computer program


  An ordered set of instructions to be performed by a computer
• Computer program

  The solution to an existing problem
• Computer program execution


  1. Fetch instruction

  2. Execute

  3. Repeat
• High level language


  e.g. Python
• Low level language


  e.g. machine code
• Integrated Development Environment (IDE)

  Allows all tasks to be carried out in one application
• IDE


  • Main reason we use an IDE is the Solution explorer
  • Debugger detects and corrects errors
  • GUI with toolbox
  • Source code editor
• Source code editor


  • A basic window that allows you to enter source code
  • Provides developer with a clipboard, code auto-completion, code suggestion and syntax error assistance
• IDE


  • Allows programmer to create windows applications on-screen
  • Contains buttons and combo-boxes giving 2 views of the GUI (Graphical or code based)
• Compiler


  • Turns written program into an executable file
  • Converts written program code into machine code so it can be executed
  • Program must be error-free to be compiled
• Translation of code


  1. Code written in high level language can only be understood by humans

  2. Must be translated into machine code so the computer can execute it
• Types of translation


  • Interpreter
  • Compiler
  • Assembler
• Interpreter


  • Translates source code programs line by line
  • Must be translated completely before proceeding to the next line
  • Errors are debugged as they are found
• Compiler


  • Converts the whole program into machine code before executing the whole program at once
  • If the program contains errors, they are listed together by the computer
• Assembler


  • Translates assembly language into machine code
  • Assembly language is already a low level language
• Role of the compiler

  1. Lexical analysis - converting source code to fixed length binary tokens

  2. Pre-processing - including library code for classes within the source code

  3. Syntax analysis - checks that all statements follow the rules of grammar

  4. Semantic analysis - checking variables are declared before they are used in the program

  5. Code generation - creating the machine code from source code

  6. Code optimisation - making the executable program as efficient as possible
• Algorithm


  • A set of steps that represent the solution to a problem
  • Order of the steps is important
• Syntax


  • The rules of a programming language
  • Must be corrected before the program code can be compiled into machine code
• Variable


  • A named location in computer memory used to hold a data value while the program is running
  • Variables can hold different values during the execution of a program
  • Most programming languages require the programmer to declare all variables and state their data type
• Data types


  • Integers (whole numbers)
  • Real (decimals and fractions)
  • Character (letters, numbers, symbols)
  • Boolean (true/false)
  • String (sequence of characters)
• Sequence


  The order in which instructions are performed in a computer program
• Selection


  • The sequence of statements to be performed is determined by the input data
  • Allows decisions to be made based on the value of certain variables
• Iteration


  Looping - a sequence of code is repeated a certain number of times
• Count controlled loop


  A variable is used to control the loop, initialised and incremented each time the code loops
• Condition controlled loop


  The sequence of code is repeated until a certain condition is met
• Algorithms are used to help design the solution to a problem
• Flowchart


  • A diagrammatic representation of an algorithm
  • Contains special symbols that represent the flow and control of actions specified in an algorithm
• Class


  A template that describes the methods and properties that relate to a real world object
• Object


  • A self-contained element that relates to a real world object
  • An instance of a class which describes details of the object's properties and methods
• Property


  A data value within an object
• Method


  • A routine within an object
  • Code that defines an action an object within the class can perform
  • Methods only have access to data within their own class
• Inheritance


  • A new class can automatically have the methods and properties of an existing class
  • The new class can also define its own additional methods
• Parent/Base Class


  An existing class whose methods and properties can be inherited
• Child/Derived Class


  A class resulting from inheritance