Paper 2

• Decomposition is breaking a complex problem into lots of smaller ones
• Abstraction is simplifying a problem by removing unnecessary details
• Algorithmic thinking is coming up with a series of logical steps to create a solution
• Rounded rectangle = start or stop
• Parallelogram = inputs or outputs
• Rectangle = processes
• Diamond = decision
• Arrows must be used in flowcharts to show the flow of data
• Sequence = only one route from the beginning to the end
• Selection = having decisions creating multiple routes from beginning to the end
• Iteration = a loop that makes you repeat a task
• Linear Search

  • Searching each value in the list in order until the search is complete
• Binary search

  • (N+1)/2 and round up if needed repeated until the search is complete
  • List must be ordered first
• Binary search

  • Advantages are: efficient at searching large lists
  • Disadvantages are: list must be ordered first
• Linear Search

  • Advantages are: it's simple, it works on unordered lists
  • Disadvantages are: it is inefficient on long lists
• Bubble sort

  • Comparing and swapping values until the list is ordered
  • List is only ordered when a pass without any swaps is done
• Insertion sort

  • Adding a new value to the list in the correct place in each pass
• Merge sort

  • Split the list into sublists and order the sublists, then combine/order the sublists
• Bubble sort and insertion sort

  • Advantages are: simple and easy to implement, quick to check if list is already sorted, it doesn't need much memory
  • Disadvantages are: inefficient on large lists
• Merge sort

  • Advantages are: efficient on large lists, running time isn't effected by the order of items in the original list
  • Disadvantages are: slower on small lists, goes through the whole process even if the list is already sorted, uses more memory to make sub-lists
• Integer = whole number
• Real / Float = decimal numbers
• Boolean = true or false
• Character = one letter,symbol or digit
• String = a collection of characters
• Constant values cannot be changed whilst the program is running
• Variables are values that can be changed whilst the program is running
• Inputs receive data from a user
• Outputs display data to the user
• Div gives the whole number part of the division
• Mod gives the remainder of a division
• Logic Gates

  
• Ways to improve maintainability:

  • Write comments
  • Use indentation
  • Use descriptive names for variables
  • Use sub-programs
• Validation checks:

  • Range check
  • Presence check
  • Format check
  • Look-up table
  • Length check
• Authentication is confirming the identity of the user before allowing access
• Ways to secure passwords:

  • Create strong passwords
  • Limit the number of failed authentication attempts
  • Require frequent password changes
  • Ask for a random selection of characters from the password
• SQL

  • Columns = fields
  • Rows = Records
  • SELECT WHERE FROM
• Sub program is a set of instructions stored under one name that are executed when called.They help improve code structure, improve readability and avoid repeating code.
• Parameter is a variable used to pass data into a sub program and can be any data type
• Argument is a value a parameter takes when a sub program is called