unit 1.2part 2

• Programming paradigm


  An example of a pattern or way of doing things in computing
• Programming languages include various facilities like variables, loops, conditions, and arrays
• Programming paradigm


  Our way of doing things with programming languages
• Types of programming languages

  • Python
  • Visual Basic
  • C#
• Most programming languages are Turing complete, meaning they can solve all problems a computer can solve
• Reason for different programming paradigms

  Some problems are better suited to being solved using a certain paradigm than another
• Categories of programming languages

  • Low-level
  • High-level
• Machine code


  • Least abstracted, closest to what happens on a computer, written in binary 1s and 0s
• Assembly language


  • Uses short code words called mnemonics, one-to-one relationship with machine code
• High-level languages


  Languages that can go further than machine code and assembly language, developed from the 1950s
• Categories of high-level languages


  • Imperative
  • Declarative
• Imperative languages


  Use statements that change a program's state, focus on describing how a program operates
• Declarative languages


  Focus on what the program should accomplish
• Imperative programming paradigms


  • Procedural programming
  • Object-oriented programming
• Procedural programming


  A type of imperative programming paradigm where a program is built for one or more subroutines
• Object-oriented programming


  A more modern extension of the imperative programming approach, focusing on a modular approach
• The evolution of programming languages and paradigms has progressed from low-level to high-level, including procedural and object-oriented approaches
• There are advantages and disadvantages to machine code versus assembly language
• Procedural programming and object-oriented programming are two key imperative programming paradigms
• Procedural languages


  One of the most common programming paradigms in use
• Procedural languages are often referred to as imperative languages
• Imperative


  Literally means to give an order or an instruction
• Procedural languages


  • Focus on telling a computer exactly what to do by the way of step by step instructions
  • Lay code out as a series of statements such as sequence, selection and iteration
  • Developed in a modular way, with blocks of code identifying set tasks that need to be completed
  • Make use of procedures and functions
• In the exam, you need to be able to read, trace, amend and write procedural program code using a variety of the constructs and systems available
• Procedural languages


  The exam board doesn't actually specify which specific procedural languages you should learn, that choice is most likely up to your teacher
• Although the syntax of each procedural language is a little different, the underlying concepts are exactly the same
• Assembly language


  Substituted the binary codes with simple sequences of letters known as mnemonics
• Assembly language


  • Directly translated into binary machine code by a translator known as an assembler
  • Low level language
• Little Man Computer (LMC)


  A conceptual computer often used in education theory and exams to help students learn, test and understand the basics of assembly language
• LMC instruction set


  • 11 simple instructions on mnemonics
• Real instruction set and assembly code would contain many more instructions than the LMC
• There are many free LMC simulators on the web that allow you to practice assembly code
• Parts of the LMC interface

  • RAM main memory with 100 locations
  • Arithmetic Logic Unit
  • Accumulator to store results
  • Program counter to store address of next instruction
  • Instruction register to hold op code
  • Address register to hold operand
  • Input tray for user input
  • Output area for program output
• Program counter


  Holds 2 digits from 0 to 99
• Accumulator


  Can hold 3 digits and a sign, from -999 to +999
• Labels


  Names assigned to addresses to help write programs more easily
• Running an LMC program

  1. Enter program into simulator

  2. Press submit to convert to intermediate output

  3. Press run to execute program
• LMC computer can't tell whether memory contains instructions or data
• Modern computers can segment their memory
• Output of one program can become the instructions of another