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Begin Datablast GCSE Computing. Computer Systems Define a computer system Describe the importance of computer systems Explain the need for reliability.

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Presentation on theme: "Begin Datablast GCSE Computing. Computer Systems Define a computer system Describe the importance of computer systems Explain the need for reliability."— Presentation transcript:

1 Begin Datablast GCSE Computing

2 Computer Systems Define a computer system Describe the importance of computer systems Explain the need for reliability Explain the need for professional standards Ethical, environmental, legal issues

3 CPU Topic Key Points Purpose Fetch, Decode, Execute instructions FunctionFetch - Decode - Execute Cycle PerformanceClock speed, Caches and Cores

4 Binary Logic Why use binary? GateSymbol AND OR NOT

5 RAM vs ROM Topic Key Points RAM Currently running programs, currently used data ROMStartup instructions Issues Volatile vs non-volatile Size

6 Memory Topic Key Points CacheBuffer, small, quick RAMMain memory Virtual MemoryHard drive, large, slooow

7 Device Types Topic Key Points InputKeyboard, Mouse, Webcam, Mic OutputSpeaker, Monitor, Printer StorageMagnetic, Optical, Solid State ProcessingCPU CommunicationModem, Router

8 Storage Devices Topic Key Points MagneticHDD, Magnetic Tape OpticalCD, DVD, BluRay Solid StateMemory card, USB stick, SSD

9 Operating Systems User Interface Memory Management Peripheral Management Multi-tasking Security

10 Utility Programs Topic Key Points SecurityAntivirus, spyware, firewalls Disk organisationDefragmentation, formatting, FTP System Maintenance System cleanup, automatic updates, system info

11 Application Software Issue vs Issue Off the shelfBespoke Open SourceProprietary

12 Binary Numbers Bit - Nibble - Byte - KB - MB - GB - TB Convert Binary Denary Binary Addition Overflow Errors

13 Hexadecimal Convert Binary Hexadecimal Convert Denary Hexadecimal Advantages of Hexadecimal

14 Representing Characters Topic Key Points How it worksLookup table of values Character SetsASCII, Unicode Bits per characterAdd 1 bit, DOUBLE the range

15 Representing Images Topic Key Points How it worksPixel colours in binary Metadata Height, width, resolution, colour depth File size Resolution - Pixel density Colour depth - bits per pixel

16 Representing Sound Topic Key Points How it worksSound samples in binary Sample Rate Frequency of samples, Equivalent to resolution Bit Depth Bits per sample, Equivalent to colour depth

17 Representing Instructions Topic Key Points Machine CodeNumeric values for instructions Opcodes Code for the Operation e.g. add, store, load, branch Operand Address to be operated on e.g. #0060

18 DBMS Topic Key Points DatabasePersistent, organised store of data DBMS Database Management System Separates the program from the data Purpose Create, maintain and interrogate DB

19 Database Components Topic Key Points TablesEntities, store of data Forms Interface for the table, easy to use, view/add/edit records QueriesSearch / interrogate data Reports Organised layout, snapshot of the data

20 Relational Databases Topic Key Points Primary KeyUnique for each record Foreign KeyLinks to another table Data Redundancy Avoid duplicating data Only update one record

21 Networks Topic Key Points StandaloneNot networked LAN Local Area Network One Site Bespoke Cabling WAN Wide Area Network Separate Sites Uses Telecomms Infrastructure

22 Network Hardware Topic Key Points Network CardWired, wireless, bluetooth ModemConnect digital and analogue Hub / RouterCommunicate between computers WifiRouter, built in, dongle

23 Topologies TopicProsCons RingFew cablesEasy to break Bus Individual machines won’t break network Central bus can break network StarMost reliableLots of cabling

24 Network Terms Topic Key Points IP Address Address for each machine e.g MAC Address Permanent address for each device e.g. ethernet, wifi and bluetooth Packets Split data into small parts to send. Why? DNS Lookup table. google.com =>

25 Network Security Topic Key Points User Access Levels Installing software, accessing key files Password Policies Avoid obvious passwords, change regularly? EncryptionHTTP vs HTTPS FilteringBlocked websites

26 Network Policies Topic Key Points Acceptable UseYou signed one! Disaster Recovery Keeping the business going FailoverRedundant servers BackupOnsite, offsite, batch, sequential...

27 Webpages Topic Key Points HTML Rendering in web browsers,, consistent standard FiletypesJPG, GIF, MPG, MP3, PDF Lossless Compression Identical when recreating the file Small size saving Lossy Compression Some data - and quality - lost Significantly smaller

28 Programming Terms Topic Key Points SequenceList of instructions in order SelectionIf statement IterationWhile loop, For loop VariablesName, Type, Value

29 Data Types Topic Key Points Char & StringText IntegerWhole Number Real or Float Decimal Number (Decimal Fraction) BooleanTrue or False

30 Programming Languages TopicExample Key Points High Level if score > 200: print(“You win!”) Cross-platform Easier to read/write Assembly Languag e LDA 36 Opcode & Operand Hardware specific Easier to read/write *than machine code* Machine Code 0110 Opcode & Operand Hardware specific What the processor uses

31 Translators Topic Key Points Compiler From High Level to Machine Code Batch job - find all syntax errors Quicker to run once compiled Interpreter From High Level to Machine Code Step-by-step - Stop at first error Quicker to edit and test Assembler From Assembler to Machine Code One-to-one translation

32 Testing Topic Key Points Strategies Test the boundaries Valid, Invalid, Extreme Syntax Error Mis-typed Won’t run Logic Error Valid syntax - it runs Doesn’t do what you intended


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