Computing Revision

Computing Revision

1. Data Representation

   • Binary
     • A combination of 1's and 0's that represent different numbers
     • Base 2
     • 1 = On
     • 0 = Off
   • Hexadecimal
     • Base 16
     • A,B,C,D,E,F,1,2,3,4,5,6,7,8,9
     • Hexadecimal is an easier way of representing large numbers.
       • It is better for large numbers than binary as binary can have lots of numbers whereas Hex normally has two
   • Denary
     • Denary is basic numbers that people use everyday
       • It's a lot easier for people because computers try to minimise storage so they put them into other ways of representing data
     • Denary can be any integer possible
       • e.g. 420
     • It is also known as decimal

2. Abstraction

   • Abstraction is when you get rid of unnecessary parts of a problem or idea
     • An example of this is the tube map
       • It started off showing each individual turn and represented the exact distance between stations
         • this was then reduced to the map we know today that just shows where each train leads

3. Decomposition

   • Decomposition is when you cut down a complicated problem into many different 'sub-problems'
     • This makes the overall problem a lot easier to understand
       • This is because one big problem has been split into lots of easier problems that you just have to put back together

4. Iteration and Loops

   • Iteration is the act of repeating a process until a desired result is met
     • Program constructs that cause iteration are called loops
   • Loops are used to make a program perform an act a certain amount of times
     • Examples
       • 'For'
         • This is used to perform an action a set amount of times using the 'for x in range' loop
       • while True
         • This means that something will repeat an infinite number of times

5. Embedded systems and components

   • Embedded systems
     • An embedded system is a computer system built within a larger device
       • Computer systems are embedded in these devices. Embedded devices are limited to a certain number of tasks, unlike desktop and laptop computers which are general purpose computer systems capable of carrying out many different tasks.
   • Components
     • Input devices
     • Memory
     • Permanent, long terms memory devices
       • Hard disk drives
     • Output devices
     • Buses
       • Data is transmitted from one component to another

6. System Software

   • Computer hardware needs to be told what to do
   • This is the role of the system software
   • The CPU cannot communicate with peripherals without the help of the system software
   • If a word processing or spreadsheet program needs something to be displayed on screen or on paper, thew system software communicates with the monitor and the printer
   • If several programs are running at the same time, the system software keeps all of them running smoothly
   • Utility software helps with maintenance jobs such as defragmenting the hard disk drive, compressing files and improving security