Topic 2 Hardware Revision

Topic 2 Hardware Revision

1. Input and Output devices

   • Input
     • Definition: An input device is a piece of hardware that is used to enter data into a computer
     • Examples: Keyboard, mouse, digital camera/web cam, barcode scanner
       • RFID readers (Radio Frequency Identification); an electronic version of a bar code. It uses radio frequencies to transfer information to a reader.
   • Output
     • Definition: An output device is a piece of hardware that is used to display or output data that has been processed or stored on the computer.
     • Examples: monitor, speakers or headphones, printer
       • Actuators: are a device, controlled by a computer that can affect the real-world
   • Both
     • Examples: Tablet computers, head set
   • Specific needs
     • foot mouse: a way for people with no or little use of their upper limbs to use a mouse with their feet.
     • Puff-suck switch:a way for people to activate simple switches on a computer with a simple puff, it is useful for people with no use of their limbs.
     • Eye typer: is a device that sits atop or by the side of the monitor which tracks the pupil movement that moves the cursor on screen and is chosen by a blink.

2. Secondary storage

   • Definition: it is a form of storage that is non-voiatile and stores things like: documents, programs and the operating system.
   • It is needed to store any work, programs and OS that you or the computer needs.
   • Internal storage: is built into the computer and is only used for that computer, it is also quicker than removable storage.
   • External storage: refers to storage that can be taken away. Sometimes only the medium on which the data is stored (E.G. a CD) is removed.
   • Magnetic hard drive: stores data as magnetic fields. Metal platters spin thousands of times a second while magnetic readers and writers store and read data. It has direct data access, magnetic based, and Hard disks hold a large amount of data and are relatively cheap. It is one of the quickest to access and especially when it's internal.
   • Optical disks: An optical disk is something like CDs and DVDs they work by a laser burning into them and is read also by a laser. They are also very cheap to make, CDs hold around 650mbs but a DVD can hold around 9Gbs if it is double layered. They are very portable but are susceptible to scratching and snapping making them less reliable.
   • Tape storage: tape storage uses serial access to store data. This means that the tape has to start from the beginning and fast-forward to the data you want. This makes it useful for large companies to archive their data as it can store masses of data that doesn’t need to be immediately retrieved. They are also the cheapest form of storage.
   • Solid state memory (flash memory): It’s small and light weight, is very reliable and involves no moving parts. It is the fastest form of storage but has a limited life span.

3. The CPU

   • Definition of the purpose: is to process data and to control the operations of the computer.
   • Fetch-Execute cycle
     • Fetching: data from the computers main memory then store them in its own registers.
     • Decoding: data decodes the instruction and prepares various areas within the chip in readiness of the next step.
     • Executing: instructions are carried out upon the data (Executed).
     • Once the execute stage is complete, the CPU sets itself up to begin another cycle once more.
   • Components
     • The ALU: carries out calculations and makes decisions on the data sent to the processor. This is where the computer processes data either by manipulating it or acting upon it.
     • Registers: is a small amount of fast temporary memory within the processor where the ALU or the CU can store and change values needed to execute instructions.
       • One important register is the program counter. This keeps track of the running order of the instructions and shows which instruction in the program is due to be executed next.
       • The CPU needs registers as it is too slow to be able to run applications directly from the computers main memory (RAM).
     • The control unit (CU): The CU, which is also called the controller, controls data moving through the processor, and controls the timing of operations and the instructions sent to the processor and the peripheral devices. The CU directs the system to carry out program instructions. It does the fetching, decoding, and managing of instructions.
   • Cores: A CPU can contain one or more processing units. Each unit is called a core. Each core contains an ALU, Control unit and registers. It is common for computers to have two (dual), four (quad) or even more cores. CPUs with multiple cores have more power to run multiple programs at the same time.
   • Clock speed: Computers can only do one thing at a time The CPU processes data and instructions using the fetch-decode-execute cycle. The clock speed is the time it takes to process instructions. With every tick of the clock, the CPU is able to process one piece of data or execute one instruction. This is measured in gigahertz (gHz).
   • Overclocking:
     • A computer will normally have a maximum clock speed set by default, but it is possible to change this speed in the computer BIOS. Some people increase a CPU clock speed to try to make their computer run faster - this is called overclocking.
     • If the clock tells the CPU to execute instructions too quickly, the processing will not be completed before the next instruction is carried out. If the CPU cannot keep up with the pace of the clock, the data is corrupted.

4. Binary logic

   • NOT Gate:
   • AND Gate:

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