Chapter 4

Chapter 4

1. Modelling

   • Model - an artificial re-creation of an object or event that should behave in the same way as the real thing.
   • Object Modelling - allows you to create a virtual representation of the item within the computer.
   • Mathematical Modelling - uses spreadsheets. Involves replication - the copying of a cell either horizontally or vertically.
   • Advantages
     • Less risky (safer and cheaper) to test.
     • Only one model needs to be created.
     • Can be backed up and shared.
     • Can be accelerated or slowed down.

2. Variables, Formulae, Rules and Functions

   • Variable – a changeable identifier associated with a particular cell.
   • Formula - the way that a calculation is represented in a spreadsheet.
   • Rules - a set of procedures that must be followed.
   • Function - represents a formula that is too complex or too long to expect an ordinary user to enter.
   • What if...? questions - an attempt to find out what is going to happen in the future.

3. Parts

   • Worksheet - large grid of cells on a single sheet.
   • Workbook - a collection of more than one worksheet in the same spreadsheet.
   • Row - a range of cells that goes across the spreadsheet. Column - a range of cells that go down the spreadsheet.
   • Cell - an individual data store identified by a column and row indicator, in that order for example A4 or AC154.
     • Labels - any text in a cell describing the data in a row or column(titles, headings that identify data).
     • Data - any values (text or numbers) that are entered for the use of calculation.
     • Formulas and functions - mathematical calculations carried out automatically.
   • Range - a group of cells. Reference range - top left cell reference: bottom right cell reference.

4. Cell Referencing

   • Relative referencing - the cell referenced in a spreadsheet formula changes when the formula is copied to other cells.
   • Absolute referencing - the referenced cell in a spreadsheet formula needs to remain exactly the same when the formula is copied to other cells.