1. Computer Applications NCBS Stage 1

2. The Central Processing UnitSlide 2Computer Applications Stage 1 Course Content and Assessment Practical – 60% (2 Hrs Weekly) –File Management –Internet –Word Processing –Spreadsheets Theory – 40% (I Hr Weekly)

3. The Central Processing UnitSlide 3Computer Applications Stage 1 The Central Processing Unit The ‘brain’ of the computer A tiny piece of silicon (chip) containing millions of transistors Getting smaller, faster and cheaper all the time

4. The Central Processing UnitSlide 4Computer Applications Stage 1 Functions of a Computer The function of a computer is to process data Processing means turning data into meaningful information Input (Data in) Processing (Calculations etc) Output (Results of processing – Information) Storage of Results

5. The Central Processing UnitSlide 5Computer Applications Stage 1 Input Data –Raw data is figures etc that can be manipulated Programs –Instructions to the computer about what to do with the data

6. The Central Processing UnitSlide 6Computer Applications Stage 1 Input devices Used to put data and programs into the computer –keyboard, disk, microphone, scanner etc

7. The Central Processing UnitSlide 7Computer Applications Stage 1 Processing Means turning raw data into meaningful information Mathematical Operations 1+1=2 Logical Operations A=6 B=4 Logical deduction A>B

8. The Central Processing UnitSlide 8Computer Applications Stage 1 Processing Takes place in the CPU Main Memory holds the data and instructions that are being used Processing needs both the CPU and Memory CPU Memory

9. The Central Processing UnitSlide 9Computer Applications Stage 1 Output The results of processing need to be output for user to see and use

10. The Central Processing UnitSlide 10Computer Applications Stage 1 Output can be sent to …. Screen Disk (floppy, zip, CD, DVD etc) Printer To another computer via a network

11. The Central Processing UnitSlide 11Computer Applications Stage 1 The Parts of the CPU These parts make up the CPU Control Unit ALU Registers Control unit Arithmetic/Logic Unit Registers

12. The Central Processing UnitSlide 12Computer Applications Stage 1 The Control Unit This controls everything that happens inside the computer It transfers data and program instructions between the Memory and the ALU It sends the results back to Memory and later to a storage device

13. The Central Processing UnitSlide 13Computer Applications Stage 1 The Arithmetic/Logic Unit (ALU)… Performs either mathematical or logical operations –Addition, subtraction, multiplication etc –Greater than, less than etc The ALU produces results

14. The Central Processing UnitSlide 14Computer Applications Stage 1 Registers… Are temporary storage areas for data and/or instructions Data, instructions and results are held in registers for a very short time They are faster than RAM so they speed up processing Areas in the ALU and CU

15. The Central Processing UnitSlide 15Computer Applications Stage 1 Main Memory CPU Memory Main Memory is made up of RAM and ROM and is not part of the CPU Data passes in and out of RAM to be processed

16. The Central Processing UnitSlide 16Computer Applications Stage 1 Storage Anything stored in RAM is only held there temporarily - until processing is complete Permanent storage is called Secondary Storage This is needed or work would be lost as soon as the computer was switched off

17. The Central Processing UnitSlide 17Computer Applications Stage 1 Storage Devices Disks CDs DVDs Paper

18. The Central Processing UnitSlide 18Computer Applications Stage 1 Memory v Storage Memory or Main Memory is the term used for temporary storage ie RAM and is outside the CPU Registers are a type of Main Memory found in the CPU Secondary storage covers a lot of devices used for files such as disks, CDs etc

19. The Central Processing UnitSlide 19Computer Applications Stage 1 Programs Programs are sets of instructions for the computer to follow The program must be in Memory (RAM) before processing can take place

20. The Central Processing UnitSlide 20Computer Applications Stage 1 Executing/Running a Program The program must be placed in Main Memory The data must be placed in Main Memory

21. The Central Processing UnitSlide 21Computer Applications Stage 1 Running a Program Once the program and data are in place the following sequence is followed: CPU Memory 1. Fetching 2. Decoding 3. Executing 4. Storing

22. The Central Processing UnitSlide 22Computer Applications Stage 1 CONTROL UNIT ALU Registers Fetching Instructions The control unit fetches (gets) the instruction from memory. Memory

23. The Central Processing UnitSlide 23Computer Applications Stage 1 Decoding Instructions The control unit decodes the instruction It then moves the necessary data from Memory to the ALU for processing CONTROL UNIT ALU Registers Memory

24. The Central Processing UnitSlide 24Computer Applications Stage 1 Executing Arithmetic/Logic Operations The ALU performs the arithmetic or logical operation on the data All processing takes place in the ALU

25. The Central Processing UnitSlide 25Computer Applications Stage 1 Storing Results The ALU stores the result of its operation on the data in Memory or in a Register until they are output to a storage device Control Unit ALU Registers MEMORY

26. The Central Processing UnitSlide 26Computer Applications Stage 1 The Machine Cycle This is the time taken by the CPU to process a single program instruction The time is divided into 2 phases –I-time and –E-time

27. The Central Processing UnitSlide 27Computer Applications Stage 1 (I-time) Instruction Time The time it takes the Control Unit to fetch an instruction from Memory and decode it is called instruction time + Memory Control Unit ALU Memory Control Unit

28. The Central Processing UnitSlide 28Computer Applications Stage 1 (E-time) Execution Time The time it takes to carry out an ALU operation and then store the result is called execution time + ALU Memory ALU Registers

29. The Central Processing UnitSlide 29Computer Applications Stage 1 Computer Speed Computers carry out millions of instructions per second (MIPS) Processors are described in MegaHertz (MHz) and GigaHertz (GHz) These figures indicate how quickly the computer can process instructions

30. The Central Processing UnitSlide 30Computer Applications Stage 1 Conclusion and Key Words CPU ALU Registers Control Unit Main Memory RAM Data Information Program Secondary storage Machine Cycle I-time E-time

31. The Central Processing UnitSlide 31Computer Applications Stage 1 References Computing Essentials 2005 By Timothy and Linda O’Leary Computers - Tools for an Information Age By H L Capron - Ch 3 Computing in the Information Age By Stern and Stern - Ch 4