Computing Revision Resource

Computing Revision Resource

1. Computer hardware

   • The CPU
     • The brain of the computer as it is in charge of all the computer processes and calculations.
     • A CPU can have many cores. The more cores a CPU has the more cycles it can do simultaneously.
     • The more hz a CPU has the more cycles it can perform a second. A 5Mhz CPU means the CPU can perform 5 million processes a second.
     • Hz means clock speed.
     • A process is one fetch, decode and execute cycle.
       • Fetch, decode, execute cycle means the CPU fetches the data, decodes it into something the CPU can read and then executes the intruction given.
   • Binary Logic
     • How to add binary
     • How to convert binary into denary
     • How to convert binary into hexadecimal
     • When adding binary, if the outcome is longer than 8 bits then it's an overflow error.
   • Memory
     • Solid state drive (SSD)
       • Doesn't have moving parts.
       • Is more expensive than magnetic storage.
       • Found commonly in mobile devices such as laptops.
     • Magnetic storage
       • Has moving parts.
       • It doesn't cost much to get a lot of magnetic storage.
       • Found commonly in non-mobile items such as server rooms.
     • Volatile memory is memory that is wiped when the computer is turned off. An example is RAM.
     • Non-Volatile memory is memory that isn't deleted when the computer is turned off. An example is a hard drive.
   • Input and Output devices
     • Input
       • Mouse
       • Keyboard/Braille keyboard
       • Mirophone
       • Eye typer
       • Blow and suck switch
     • Output
       • Printer/Braille printer
       • Moniter
       • Speakers
       • headphones
   • Secondary storage
     • Secondary storage is non-volatile external memory. USB drives and floppy disks are examples of this.

2. Software

   • Operating systems
     • GUI stands for Graphical User Interface
     • CLI stands for Command Line Interface
     • Multi-tasking is a key feature of operating systems which allows the user to interact with the computer whilst the the operating system does jobs like manage memory in the background.
       • It also allows the user to do things such as typing in a document whilst having a tab open playing a video.
   • Utility programs.
     • Antivirus software is a utility program that has a list of malware definitions, if the software finds a program that matches those definitions then the program is quarantined until the user decides what to do with it.
     • Disk fragmenting is a utility program which gets all the data that's scatter across the hard drive and organises them.
       • This results in the computer opening up files quicker as the computer has to travel a shorter distance to retrieve the data.
     • Automatic update is a utility program which checks the internet to see if any programs need updating and will then update the program.
   • Software types
     • Off the shelf software
     • Custom written software
       • Custom written to the user's requirements.
       • Costs a lot and takes a lot time to create.
       • Will only have the features the user wants.
       • Costs a lot of money to develop.

3. Representation of data in computer systems

4. Databases

   • DBMS (Database Management System)
     • A primary key is a unique identifier in a database.
       • An example would a telephone number.
     • A foreign key is used to link tables together. These can be 'one to many' or 'many to one' links.
     • A database is a persistent and organised store of data.
     • An entity is a real world object of thing made up of many attributes
       • An attribute is a field in a table.

5. Computer communications and networking

6. Programming

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