Programming fundamentals

• Variable

  Named memory address that holds a value
• The value assigned to a constant cannot be changed whilst the program is running
• Constants are useful because they are declared and assigned once
• Global variable

  A variable that can be accessed and changed throughout the program
• Local variables

  A variable that is confined to a loop or subprogram
• Three basic programming constructs

  • Sequence
  • Selection
  • Iteration
• Sequence

  The order in which instructions occur and are processed
• Selection

  A decision within a computer program when the program decides to move on based on the results of an event
• Iteration

  The repeated execution of a section of code when a program is running
• Two types of iteration:

  • Count controlled iteration
  • Condition controlled iteration
• Count controlled iteration repeatedly executes a section of code a fixed number of predetermined times, using the statements 'for' and 'next'
• Using count controlled iteration can lead to fewer programming errors and more flexible programs
• Condition controlled iteration repeatedly executes a section of code until a condition is met, or no longer met
• Two times of condition controlled iteration:

  • While statements (uses the statements while and endwhile)
  • Repeat loops (uses the statements repeat and until)
• With a while loop, the code within the iteration may never be executed. With a repeat loop, the code is always executed atleast once
• Infinite loop

  A loop that repeats forever
• Nesting

  Including one programming construct within another
• Three types of operator:

  • Mathematical operators
  • Comparison operators
  • Logical operators
• Multiplication


  *
• Division

  /
• Integer division

  DIV
• Remainder


  MOD
• Exponentiation

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