L1

• Computers and Programming

  A computer is just a machine (the hardware) for executing programs (the software)
• Software

  Rules the hardware
• Programming

  The process of creating software
• Virtually, anyone can learn how to program computers
• Programming


  Requires only some grit
• Why Learn Programming?

  • Computers have become commonplace in our modern life
  • Understanding the strengths and limitations of computers requires some understanding of programming
  • Programming can be loads of fun!
  • Programming develops valuable problem-solving skills, especially ones that pertain to analysis, design and implementation
  • Programmers are in great demand!
• Fields where programming is applied

  • Gene Sequencing and Biotechnology
  • Smaller, Faster, Cheaper Sensors
  • Astronomy
  • Ubiquitous Computing
• Hardware Basics


  To be a successful programmer, you need to know some details of how computers work
• Performance

  Efficiency of a program
• Memory


  Where data and programs are stored
• CPU-bound

  When a program's performance is limited by the CPU
• IO-bound

  When a program's performance is limited by input/output operations
• Functional View of a Computer

  • Input Devices
  • CPU
  • Main Memory
  • Output Devices
  • Secondary Memory
• Secondary Memory


  Where saved program and data reside, non-volatile storage
• Main Memory

  Much faster but more expensive than secondary memory, volatile storage
• CPU

  The "brain" of the computer, can perform arithmetic and logical operations, can directly access main memory but not secondary memory
• Input and Output Devices

  • Keyboard and mouse
  • Monitor
• Input and Output (IO)

  Humans interact with computers via input and output devices, information from input devices is processed by the CPU and may be stored in memory, information to be displayed is sent from the CPU to output devices
• Program


  A sequence of instructions telling the computer what to do
• Programming Language


  A language that computers can understand, examples are Python, Java, C, and C++
• Syntax

  The exact form of a structure in a programming language
• Semantics


  The precise meaning of a structure in a programming language
• Machine Language


  The very low-level language that computer hardware can only understand
• High-Level Language


  Languages like Python, Java, C, and C++ that are more human-oriented than machine language
• Adding two numbers in machine language

  1. Load the number from memory location 2001 into the CPU

  2. Load the number from memory location 2002 into the CPU

  3. Add the two numbers in the CPU

  4. Store the result into location 2003
• c = a + b

  How addition of two numbers is expressed in a high-level language like Python
• Compiler

  A complex software that translates a program written in a high-level language into an equivalent program in the machine language
• Interpreter

  A software that analyzes and executes the source code instruction-by-instruction (on-the-fly) as necessary
• Compiling vs. Interpreting

  • Compiling is a static (pre-execution), one-shot translation
  • Interpreting is dynamic (happens during execution)
  • Compiled programs tend to be faster
  • Interpreted programs lend themselves to a more flexible programming environments (they can be developed and run interactively)
• Portability


  The advantage that high-level languages have over machine languages, a program written in a high-level language can be run on many different kinds of computers as long as there is a suitable compiler or interpreter
• Python programs are said to be portable
• Computer


  A universal information-processing machine, which can carry out any process that can be described in sufficient detail
• Algorithm

  A description of the sequence of steps for solving a particular problem
• Software


  Programs that determine what the hardware (physical machine) can and does accomplish
• Basic Functional View of a Computer System

  • Central Processing Unit (CPU)
  • Main Memory
  • Secondary Memory
  • Input Devices
  • Output Devices
• CPU

  The brain of the computer that performs simple arithmetic and logical operations
• Main Memory

  Where data and programs are stored
• Secondary Memory


  Where more permanent information is stored
• Programming Language

  A formal notation used to write programs, has precise syntax (form) and semantics (meaning)
• Machine Language


  The very low-level language that computer hardware only understands