Higher Computing NAB revision slides for computer systems unit 1

1. Higher Computing NAB REVISION

5. Table of Bit Depth 2 4 = 16 colours 2 8 = 256 colours 2 16 = 65,536 colours True Colour 2 24 = 16,777,216 colours

8. Processor Structure Control ALU Registers Cache Main Memory Backing Storage Address bus Data bus Control bus

11. Memory Read Operation Cache Main Memory Backing Storage Address bus Data bus Address bus loaded with address of the required memory location The processor activates the READ line on the control bus READ line activated CONTROL BUS The contents of the memory location are transferred along the data bus into the processor If it is an instruction, it is DECODED and EXECUTED in the processor FETCH/EXECUTE CYCLE ***Use arrow keys to control animations*** Control ALU Registers

13. Memory Write Operation Cache Main Memory Backing Storage Address bus Data bus WRITE line activated CONTROL BUS FETCH/EXECUTE CYCLE ***Use arrow keys to control animations*** The processor sets up the address bus with the address of the required memory location The processor sets up the data bus with the data to be written to memory The processor activates the WRITE line on the Control Bus The data is transferred along the data bus to the memory location Control ALU Registers

17. Buffer Laser Printer Data to be printed is sent by the FAST processor to the SLOWER functioning printer Buffer Data is stored in the Buffer until the printer is ready to print it. When the printer has ‘caught up’ it requests the data to be printed from the Buffer ***Use arrow keys to control animations*** Not suitable for Network Printing Computer System

18. Spooling Laser Printer File to be printed PROCESSOR HARD DISK Stored temporarily here ***Use arrow keys to control animations*** Suitable for Network Printing

19. Parallel Interfaces Many bits are send down parallel lines – faster than serial transmission ***Use arrow keys to control animations*** 0 1 0 1 0 1 1

20. Serial Transmission 0 One bit is sent down a single line – slower, but more robust than parallel ***Use arrow keys to control animations***

21. Client/Server Network All data goes through the central SERVER CLIENT CLIENT CLIENT CLIENT CLIENT SERVER

22. Peer to Peer Network Want to send a file from one computer to another? The file will go from computer to computer on the network until it reaches its destination. Computer 2 Computer 1 Computer 4 Computer 3

23. Routers/Hubs/Switches A Hub splits a signal down 2 or more channels. Hubs split the signals ‘blindly’ whilst Switches forward data packets down the exact channels more intelligently HUB/SWITCH Network 1 Network 2 Router A router sends data packets between different networks using the Internet Protocol (IP) ROUTER ***Use arrow keys to control animations***