Computer Science Hardware Notes PDF

1 BRIGHTWAY INTERNATION SCHOOL Chapter3: Hardware Computer Architecture Central processing unit (CPU) The CPU has the responsibility for the execution or processing of all the instructions and data in a computer application...

1 BRIGHTWAY INTERNATION SCHOOL Chapter3: Hardware Computer Architecture Central processing unit (CPU) The CPU has the responsibility for the execution or processing of all the instructions and data in a computer application The CPU is able to access the memory directly The three important parts of the CPU are: ALU, CU, Registers Microprocessor A microprocessor is a type of integrated circuit on a single chip This performs similar role to a CPU, but on a smaller scale Von Neumann structure of fetch–decode–execute cycle The following components of CPU have major roles in Fetch-Decode-Execute cycle Registers are used to store data temporarily during the processing Example: PC, MDR, MAR, CIR, ACC Bus is a collection of wires through which data is transmitted from one part of a computer to another Example: Address Bus, Data Bus, Control Bus Control unit and Arithmetic Logic Unit (Refer the Table) The fetch stage The input data is stored in RAM / stored data in HDD is brought to RAM to be processed Then the data is brought into the CPU from RAM A component of CPU, called PC(Program Counter) stores an address of the next instruction/data Chapter3: Hardware Notes Computer Science 0478  2 The address stored in the PC is sent to another component in the CPU called MAR (Memory Address Register) The address is transported from the PC to the MAR using the address bus The address then is sent to a component within the CPU called MDR (Memory Data Register) using the data bus When the MDR has received the instruction, it sends it to the CIR (Current Instruction Register) using the Data bus The CIR is part of the CU(Control Unit), the CU is responsible for the next stage that is Decoding, The Decode stage The decode of the cycle begins when the instruction is received by the Control Unit Control Unit decodes an instruction using instruction set controls the flow of data around the CPU The Control Unit also sends control signals to the different components instructing them what to do eg; read, write, add, subtract Controls the timing of operations (the clock speed) The execute stage Arithmetic Logic Unit (ALU) is the component in the CPU that performs all the mathematical and logical operations required when processing data and instructions ACC(Accumulator) the special register built into ALU, stores interim values of calculations, once the data is performed it is sent to either HDD or display Components of the CPU Components Description Program Counter (PC) This register stores the address of the next instruction to be processed Memory Address This register stores the address of the data that needs to be processed Register (MAR) Memory Data Register This register stores data which has been fetched from memory (MDR) Control Unit (CU) controls the flow of data, decodes and executes instructions Current Instruction This register stores the current instruction being decoded and executed Register (CIR) Arithmetic Logic Unit The Arithmetic & Logic Unit (ALU) allows the required arithmetic (+,-,*,/ and (ALU) shifting) or logic (e.g. AND, OR) operations to be carried out while a program is being run Accumulator (ACC) The register built into ALU, used to store interim data when carrying out ALU calculations Chapter3: Hardware Notes Computer Science 0478  3 Address Bus the address bus carries addresses throughout the computer system. Between the CPU and memory, the address bus is unidirectional (i.e. bits can travel in one direction only) Data Bus The data bus is bidirectional (allowing data to be sent in both directions along the bus) This means data can be carried from CPU to memory (and vice versa) and to and from input/output devices Control Bus The control bus is also bidirectional. It carries control signals from the control unit (CU) to all the other computer components Core, Cache and Clock speed in a CPU and How they can affect performance of CPU Number of cores: The CPU is used to perform fetch-decode-execute cycle at a time. If a system has two cores (dual cores) it can perform two fetch-decode-execute cycle. Some CPUs have four cores (quad core processor) and can perform four fetch- decode-execute cycles all at the same time. With multiple cores, its performance can be increased Clock Speed: A CPU contains an internal clock that controls the speed at which instructions are processed. A CPU that has a clock speed of 1 hertz is able to process one instructions per second that’s bit slow, most modern computers have clock speed of 2GHz that can process 2 billion instructions a second. If a computer has a 2 cores, each core process 2 billion instructions a second Size of the Cache: it is a type of data storage within the CPU. Instructions and data that the computer uses frequently can be stored in the cache. That means that the CPU doesn’t need to fetch this data from the memory, just from the cache, so that process will be quicker, saves time to fetch data from RAM Instruction Set Instruction set is a set of all the commands that are understood and can be processed by the CPU. These commands are in machine code. Once the instruction is decoded using the instruction set, it can now be executed instructions are a set of operations which are decoded in sequence. Each operation will instruct the ALU and CU what to perform. An operation is made up of an opcode and an operand. Chapter3: Hardware Notes Computer Science 0478  4 Opcode: The opcode informs the CPU what operation needs to be done Operand: The operand is the data which needs to be acted on Since the computer needs to understand the operation to be carried out, there is actually a limited number of opcodes that can be used; this is known as the instruction set Embedded System An embedded system is different to a general purpose computer system like a laptop or desktop computer which can be used to perform many different tasks. A microcontroller is often built into a system that is designed to perform a very specific task. This type of system is called an embedded system. Embedded system runs on a firmware which provides basic machine instructions that allow the hardware to function. For example: a traffic light, a washing machine and a digital alarm clock, security system Features of Embedded System  It is built into a device  It has single purpose  It runs on firmware  It does not have additional peripherals There are many advantages of embedded systems  low power consumption  small physical size  low cost to manufacturer  they can be controlled remotely  can operate in real time and respond to inputs very quickly Input Devices Input Devices Description Key Board An input device used to enter characters and functions into the computer system by pressing buttons, or keys. Optical Mouse A computer pointing device that uses a light-emitting diode (LED) to track movement Micro Phone a device that translates sound vibrations in the air into electronic signals Digital Camera A digital camera uses an electronic image sensor to create still photographs and record video 2D Scanner usually used to make digital copies of documents or pictures 3D Scanner the process of analysing a real-world object or environment to collect three dimensional data of its shape and possibly its appearance Bar Code Reader A barcode is a series of dark and parallel lines of varying thicknesses Barcode is read by a red laser Directing a beam of light across the bar code and measuring the amount of light that is reflected back dark lines reflect little light white lines reflect more light Reflected light is read by sensors Pattern is generated by reflected light which is converted to digital format How barcode can help supermarket to manage its stock automatically Chapter3: Hardware Notes Computer Science 0478  5 Barcode reader scans and identifies product through barcode number Barcode reader is used to look up product in a database Once found, a product is deducted from the system Checks if total stock is below certain level it sends alert or automatic reorder when stock is low Once new order arrives, Barcode reader automatically update new stock level QR (Quick Response) Code It’s an advanced version of barcode Barcode has no.of lines while QR code has no.of squares Uses position and alignment markers for scanning. Can be scanned by mobile camera app Light is reflected back, black squares reflects less light, white squares reflect more light, pattern is generated by reflected lights which is converted into digital format There are three squares at the corner in QR code which represent what format of data it has like website address, contact number, email etc. Other small squares have the supportive data It has a faster readability and greater storage capacity compared to Barcode Reader Touch Screen Screens are sensitive to pressure A user interacts with the computer by touching pictures or words on the screen There are three types of touch screen technology a) Resistive b) Capacitive c) Surface Wave/Infra Red Resistive  Uses multiple layers of material that transmit electric currents  The layers are separated by air or inert gas  When the top layer is given pressure by a touch, the top layer is pressed into the bottom layer to change electric current  The point of contact is detected where there was a change in voltage Benefits: Easier technology and Cheaper to manufacture Can use stylus/gloves Drawbacks: Poor visibility in sunlight Vulnerable to scratching Capacitive Sensors are located around the screen Since human skin is a conductor of electricity, when bare fingers touch the screen, the electrical field changes Current sent out from all four corners of the screen The location of “touch” is calculated Benefits: Good visibility in sunlight More Longevity and faster response times Chapter3: Hardware Notes Computer Science 0478  6 Drawbacks: Screen is easily shattered Cannot use when wearing gloves Infra Red / Surface Wave  It has an invisible grid on the screen with sensors  The sensors detect infrared beams radiation  Sensors detect the “touch” whenever there is a break in the infrared  The position of the touch is calculated Benefits: Good visibility in sunlight Can use stylus/gloves and faster response times Drawbacks: Expensive Screen is easily shattered Output Devices Output Devices Description Actuator An actuator is a motor that converts energy into torque(rotation force) which then moves a mechanism Inkjet Printer produces hard copies of a text document or photo by spraying droplets of ink onto paper Laser Printer Uses laser technology to produce high-quality printed output. Laser printers use a toner cartridge filled with powdered ink (toner) to create images and text on paper. 3D Printer Built up layer by layer, using powdered plastic, resin and ceramic powder to produce solid object Speaker A device for converting electrical energy into acoustical signal energy that is radiated into a room or open air. LED Screen LEDs uses an array of light emitting diodes as pixels, arranged behind the screen. It has a bright color, does not consume much power, More Longevity, Thin and Lightweight. More Expensive, Generate more heat in high brightness LCD Screen Made up of tiny liquid crystals. Reduces Glare and Reflection, excellent image quality and color accuracy. Slower Response times Limited color reproduction DLP Projector Uses DMD(Digital Micro mirror Device) chip and millions of micro mirrors to determine the resolution of the image LCD Projector Older technology than DLP projector Chapter3: Hardware Notes Computer Science 0478  7 Memory Devices Primary Devices It is the main memory in which data is stored for quick access. Internal and Directly accessible by the CPU. It is both volatile and non-volatile Ex; RAM and ROM RAM (Random Access Memory) It is a Volatile memory Temporary memory It Can be read Currently storing data user typing on Currently running/storing software and parts of Operating system ROM (Read Only Memory) It is a Non-volatile Permanent memory Data stored cannot be altered It stores BIOS (Basic Input Output System) It stores Start up instructions of computer Secondary Storage Devices Secondary storage device is a non-volatile memory that holds data until it is deleted. It can be internal or external Not directly accessible by the CPU Stores files and software Ex; HDD, SSD, Pen drive, CD, DVD etc HDD(Hard Disk Drive) SSD(Solid State Drive) Magnetic Storage device Flash Storage device Creates noise It’s Quiet Slower read and write speed Faster read and write speed Capable of more Read/write cycles has limited read/write cycles Has more moving parts No moving parts Cheaper and Robust Expensive, Portable and light weight Has higher power consumption Less power consumption Higher heat production Low heat production Greater longevity and Trusted Takes less time to warm up technology Types of Memory Devices Three Types of memory Devices and its examples Magnetic Storage Device: HDD Optical Storage Device: CD, DVD, Blu-Ray Flash storage Device: SSD, Pen Drive, USB devices Magnetic Storage Devices Has more moving parts such as head, platter and spindle The platter is a rotating disc which divided into tracks and sectors Chapter3: Hardware Notes Computer Science 0478  8 It has more read/write heads that can move across platter’s surface Data is read and written using electromagnets It uses an electromagnet to magnetize dots on each platter that stores that data If a dot is magnetized it stores the binary value1. If a dot is demagnetized it stores the binary value 0. Each platter has billions of these magnetized dots Optical Storage Devices Data is represented on the surface using pits and lands pits represent 0 and lands represent 1 Laser light points at the disk as it spins, reflected light is captured by photoelectric cell When laser light hits pits, it doesn’t reflect, stores the binary value 0 When laser light hits lands, it reflects light and stores the binary value as 1, optical devices can determine binary values from light reflections Flash Storage Devices Stores data by controlling the movement of electrons within NAND or NOR chips Stores data by flashing it onto the chip Contains cells and transistors that are laid out in a grid, transistors are wired together, the intersection of rows and columns of transistors are the cells The data is stored as 0’s and 1’s in millions of tiny transistors within the semiconductor chip The electric current reaches the control gate and flows through to the floating gate for the data to be stored. Transistors are used as Control gate and floating gate When a solid state storage device is first created, all the transistors are set to the binary value 1. When data is stored in a transistor, it is converted to the binary value 0. Virtual Memory One of the problems associated with memory management is the case when processes run out of RAM. If the amount of available RAM is exceeded due to multiple programs running, it is likely to cause a system crash. This can be solved by utilising the hard disk drive (or SSD) if we need more memory. This is the basis behind virtual memory. Essentially RAM is the physical memory, while virtual memory is RAM + swap space on the HDD/SSD.  The Hard drive is partitioned to create a virtual memory when RAM is full  The oldest data is transferred to HDD/SSD from RAM, allows newest data to be processed  When the oldest data is required again, it is transferred back to RAM Without virtual memory Chapter3: Hardware Notes Computer Science 0478  9 With virtual memory Virtual memory now moves the oldest data (program 0) out of RAM into the HDD/SSD to allow program 4 to gain access to RAM. Notice the use of the 32-bit ‘map’. When a program in memory tries to access RAM, it is sent to the ‘map’, which then allocates the program address space in RAM Benefits of using Virtual memory Drawbacks of using virtual memory Allows a computer to process the large Causes a Hard disk/SSD thrashing (overuse may result in amount of data total collapse) when processing large amount of data To stop a software from crashing when RAM Accessing data is slower is full Extends RAM capacity Cloud Storage  Cloud storage is a method of data storage where data is stored on remote servers.  The same data is stored on more than one server in case of maintenance or repair, allowing clients to access data at any time  Data is normally accessed through internet connection  Instead of saving data on a local hard disk or other storage device, a user can save their data ‘in the cloud’. Benefits of using cloud storage Drawbacks of using cloud storage Files stored on the cloud can be accessed at any If a user has a slow or unstable internet time from any device anywhere in the world connections, they would have many problems accessing files No need to carry an external storage device Costs can be high if large storage capacity is required Stored Files on cloud can be accessed remotely The potential failure of the cloud storage company is always possible If user has a failure hard disk, cloud storage will allow recovery Offers almost unlimited storage capacity Chapter3: Hardware Notes Computer Science 0478  10 Sensors Sensors are input devices which read or measure physical properties from their surroundings. Examples include temperature, pressure and acidity level Sensor Description Application 1 Gas most common ones are oxygen or monitor oxygen and carbon carbon dioxide sensors; they use dioxide levels in a greenhouse various methods to detect the gas monitor oxygen levels in a car being monitored and produce exhaust outputs that vary with the oxygen or carbon dioxide levels present 2 Light these use photoelectric cells that switching street lights on or off produce an electric light depending depending on light levels on the brightness of the light switch on car headlights automatically when it gets dark 3 Infra red these use an invisible beam of turn on car windscreen wipers infrared radiation picked up by a automatically when it detects rain on detector; if the beam is broken, then the windscreen there will be a change in the amount security alarm system (intruder of infrared radiation reaching the breaks the infrared beam) detector (sensor) 4 Pressure a pressure sensor is a transducer and weighing of lorries at a weighing generates different electric currents station depending on the pressure applied measure the gas pressure in a nuclear reactor 5 Temperature measures temperature of the control/monitor a chemical surroundings by sending signals; process these signals will change as the control/monitor temperature in a temperature changes greenhouse 6 Proximity these sensors detect the presence of detect when a face is close to a a nearby object mobile phone screen and switches off screen when held to the ear Automatic door system 7 PH these measure acidity through monitor/control acidity levels in changes in voltages in, for example, the soil in a greenhouse soil control acidity levels in a chemical process 8 Magnetic these sensors measure changes in detect magnetic field changes in magnetic fields – the signal output mobile phones field will depend on how the magnetic used in anti-lock braking systems in field changes cars 9 Acoustic/sou these are basically microphones that pick up the noise of footsteps in a convert detected sound into electric security system nd signals/pulses detect the sound of liquids dripping at a faulty pipe joint 10 Acceleromet these are sensors that measure used in cars to measure rapid acceleration and motion of an deceleration and apply air bags in a er crash Chapter3: Hardware Notes Computer Science 0478  11 application, i.e. the change in used by mobile phones to change velocity between portrait and landscape mode 11 Flow(Rate) these sensors measure the flow rate used in respiratory devices and of a moving liquid or gas and inhalers in hospitals produce an output based on the measure gas flows in pipes (for amount of liquid or gas passing over example, natural gas) the sensor 12 Level these sensors use ultrasonic to Monitor height of water in river detect changing liquid levels and a tank monitor levels in a petrol tank in a car 13 Moisture measures water levels in, for control/monitor moisture levels in example, soil soil in a greenhouse monitor the moisture levels in a food processing factory 14 Humidity this is slightly different to moisture; monitor humidity levels in a this measures the amount of water factory manufacturing microchips vapour in sample of air monitor/control humidity levels in the air in a greenhouse Network Hardware Network Interface Card (NIC)  The computer hardware that is used to connect it to a network  This may be wired or wireless  Most modern NICs are wireless NICs (WNICs) Media Access Control (MAC)  Hardware identification number that uniquely identifies a device on a network  MAC address is assigned by manufacturer and is never changed  Every device has 12 digits in combination of numbers and letters called hexadecimal. Ex, 00:0d:83:b1:c0:8e  First six digits is the id no of the manufacturer and the second half represents the identity of the device  Hexadecimal numbers used as Millions of network devices are in existence Router  A router can connect local network to the internet  It is a hardware device that reads each data packet that it receives  It uses IP addresses to send data packets only to its correct destination  it can assign IP addresses to its connected multiple devices Chapter3: Hardware Notes Computer Science 0478  12 IP (Internet Protocol) Address  uniquely identifies location of a device on the network  IP address is assigned by the network(Router)  Address is unique for given internet session, Address is supplied when a device connects to the internet  IP has two types, IPv4 and IPv6  Can be dynamic or static. Dynamic changes each time the device is connected to network whereas static remains same unless user requests to change IPv4 IPv6 IPv4 is the old structure that used 32- New structure that used 128-bits, contains bits, Denary based Ex;165.268.1.1 Hexa decimal Ex; IPv4 digits are between 0 and 255 2001:0db8:0000:0000:0000:ff00:0042:7879 It has 4 sets of numbers separated by IPv6 digits are between 0000 and FFFF dots It has 8 sets of numbers separated by It can be static or dynamic colons It can be private or public It can be static or dynamic It can be private or public Chapter3: Hardware Notes Computer Science 0478