Programming

• Data type


  A data type is defined by:

  • the values it can take
  • the operations which can be performed on it

  It is sometimes possible to store one piece of data using different data types.
• Integer


  A whole number, positive or negative, including zero
• Real/float


  A positive or negative number which can have a fractional part.
• Boolean


  A value which is either true or false
• Character


  A single number, letter or symbol
• String


  A collection of characters
• Date/time


  A way of storing a point in time, many different formats are used
• Pointer/reference


  A way of storing memory addresses
• Records 


  A collection of fields, each of which could have a different data type
• Arrays


  A finite, indexed set of related elements each of which has the same data type
• User-defined data types


  • Derived from existing data types
  • Ensures that a solution is as memory efficient as possible
• Variable declaration


  Creating a variable for the first time, giving it a name and sometimes a data type
• Constant declaration


  Creating a constant for the first time, giving it a name and sometimes a data type
• Assignment


  Giving a constant or variable a value
• Iteration


  Repeating an instruction
• Selection


  Comparing values and choosing an action based on those values
• Subroutine


  A named block of code containing a set of instructions designed to perform a frequently used operation.
• Definite iteration


  The number of repetitions required is known before the loop starts
• Indefinite iteration


  The number of repetitions required is not known before the loop starts
• Nested structures


  Selection structures and iteration structures can be nested:

  • One structure is placed within another
  • This can easily be identified by different levels of indentation in code
  • Indentation makes the code easier for humans to understand
• Meaningful identifier names


  Constants, variables and subroutines should be given sensible and meaningful identifier names

  • This makes it easier for others to understand what the purpose of the named object is
• Addition


  Adding together two numbers
• Subtraction


  Taking one number away from another
• Multiplication


  Multiplying two numbers together
• Real/float division


  Dividing one number by another
• Integer division


  The same as real/float division, but just the whole number part is given
• Modulo

  Returns the remainder of an integer division
• Exponentiation


  Raising one value to the power of another
• Rounding


  Limiting the degree of accuracy of a number
• Truncation


  Removing the decimal part of a number, never rounding up
• Equal to


  e.g., 12 = 12
• Not equal to


  e.g., 16 <> 413, 16 != 413
• Less than


  e.g., 75 < 422
• Greater than


  e.g., 19 > 18
• Less than or equal to


  e.g., 6 <= 22, 95 <= 95
• Greater than or equal to


  e.g., 20 >= 126, 44 >= 44
• Boolean operations: NOT


  The opposite of a Boolean value e.g., NOT 1 = 0
• Boolean operations: AND


  The product of two Boolean values e.g., 1 AND 1 = 1, 0 AND 1 = 0
• Boolean operations: OR


  The sum of two Boolean values e.g., 1 OR 0 = 1, 1 OR 1 = 1, 0 OR 0 = 0
• Boolean operations: XOR


  True if strictly one of two values is true e.g., 1 XOR 1 = 0, 1 XOR 0 = 1