CS UNIT 3

Hardware: Computers and Their Components

• Memory cache is a high-speed memory external to the processor; it stores data that the processor will need again.
• RAM (Random Access Memory) is a primary memory unit that can be written to and read from.
• ROM (Read-Only Memory) is a primary memory unit that can only be read from.
• DRAM (Dynamic RAM) is a type of RAM chip that needs constant refreshing.
• SRAM (Static RAM) is a type of RAM chip using flip-flops and does not need refreshing.
• Refreshing is the requirement to charge a component to retain its electronic state.
• PROM (Programmable ROM) is a type of ROM chip that can be programmed once.
• EPROM (Erasable PROM) is a type of ROM programmable more than once using ultraviolet (UV) light.
• HDD (Hard Disk Drive) is a magnetic storage device using spinning disks.
• Latency is the lag in a system, like the time to find a track on a hard disk; depends on how long the disk takes to rotate to its read-write-head.
• Fragmented refers to data stored in non-consecutive sectors, which could be due to editing/deleting data.
• A removable hard disk drive is a portable hard disk external to a computer; it connects via USB and backs up files and data.
• An SSD (Solid State Drive) is storage media with no moving parts, relies on electron movement.
• EEPROM (Electronically Erasable Programmable Read-Only Memory) is ROM that the user can modify, and be erased/re-written repeatedly with pulsed voltages.
• Flash memory is an EEPROM, mainly for use in SSDs, memory cards, and memory sticks.
• Optical storage involves CDs, DVDs, and Blu-ray Discs using laser light to read/write data.
• Dual layering is used in DVDs, uses two recording layers.
• Birefringence is a reading issue in DVDs where laser light refracts into two beams.
• Binder 3D printing is a 3D printing method using a two-stage pass; it first uses dry powder, and then uses a binding agent.
• Direct 3D printing is a 3D printing method where the print head moves in the x, y, and z directions; melted material layers are built with nozzles like an inkjet printer.
• A DAC (Digital to Analogue Converter) converts digital data into electric currents to drive motors, actuators, and relays.
• An ADC (Analogue to Digital Converter) converts analogue data (like from sensors) into a form the computer understands.
• OLED (Organic LED) uses electron movement between the cathode and anode to make an on-screen image.
• OLED generates its own light, so no back-lighting is required.
• Screen resolution is pixels in the horizontal and vertical directions on a computer screen.
• A touch screen uses finger/stylus touch for selection/manipulation of a screen image; these use capacitive/resistive technology.
• Capacitive touch screens use glass layers forming a capacitor; the finger touching the screen causes change in the electric field.
• Resistive touch screens involve a finger touching the screen, the glass touches the plastic layer, completing the circuit and enabling current flow.
• A virtual reality headset is worn that covers the eyes like goggles, giving the sensation of being there, immersing you in virtual reality.
• A sensor is an input device that reads physical data from its surroundings.

Types of Memory and Storage

• Computers require memory and storage.
• Memory is usually internal to the computer for direct access; it acts as the user's workspace, for temporary data or key data for running the computer.
• Storage devices allow users to permanently store applications, data, and files, which users can change or read.
• Storage needs to be larger than internal memory, for large files.
• Memory cache (external to the processor) is also used to store data that the processor will probably need to use again.
• Primary memory is the part of computer memory that the computer can directly access from the CPU, contains ROM and RAM.
• Primary memory allows the processor to use stored locations for apps/services temporarily stored in memory.

RAM

• Computer systems come with RAM (Random Access Memory).
• RAM refers to the ability to access any memory location independent of the last memory location used.
• The larger the RAM, the faster the computer operates.
• RAM can be written to or read from, and the stored data can be changed.
• It is used to store data, files, or parts of applications/operating systems that are currently in use.
• RAM is volatile( it needs power to store the data).

Dynamic RAM

• DRAM (Dynamic RAM) chips contain many transistors and capacitors storing bits of data.
• Transistors serve as a switch, allowing chip circuitry to read/change the capacitor's value.
• If it is not refreshed, the charge will leak away quickly, leaving every capacitor with the value zero.

Static RAM

• SRAM (Static RAM) does not need constant refreshing due to the use of flip-flops to hold each bit of memory.
• DRAM has a greater number of transistors and capacitors.
• DRAM needs to be constantly refreshed.
• DRAM is less expensive to produce than SRAM.
• DRAM has a higher memory capacity than SRAM.
• Main memory comes from DRAM.
• Consumes more power than SRAM under reasonable access since it needs refreshing.
• SRAM uses flip-flops to hold each bit of memory does not require constant refreshing.
• SRAM offers faster data access times than DRAM has.
• processor memory cache comes from SRAM
• if an access occurs at a high requency, power usage can exceed that of DRAM

ROM

• ROM (Read-Only Memory)) shares random access properties with RAM but cannot be written to or changed - it is read-only memory.
• ROMs are non-volatile - the contents are not lost when powering off the computer and is a permanent memory device - contents cannot be altered.
• ROMs often store data the computer needs when powering up for the first time.
• The BIOS (basic input/output system) is stored on the ROM.
• RAM is a temporary memory device, it is volatile, and is made to write and read from.
• It is used to store data, programs and parts of OS currently in use, and increasing size improves computer speed.
• ROM is a permanent non-volatile memory device where the data is fixed and cannot be altered.
• It stores BIOS sometimes, and other data needed at start-up.
• Programmable ROM (PROM) is a type of ROM chip that can be altered once.
• Erasable Programmable ROM (EPROM) differs from PROM because it uses floating gate transistors/capacitors; ultraviolet (UV) light programs an EPROM through a quartz window.
• EPROMs are for applications under development such as new game consoles.
• Electronically erasable PROM (EEPROM)

Embedded Systems

• Embedded systems install microprocessors into devices so operations can be controlled efficiently.
• Pros of using Embedded Systems:
• Sizing is small, making it easy to fit into devices, costs remain low, tasks remain simple.
• Simple interfaces exist because there is no need for an operating system; this consumes very little power.
• Reacts fast when input changes, making it operate in real time, and mass production increases reliability.
• Cons of using Embedded Systems:
• Upgrade difficulty limits ability to use new tech, which makes fixing faults a specialist task.
• The simple interface often creates confusion (like changing the time on a cooker needing many steps).
• Any device accessed on the internet risks viruses/hackers; difficulty upgrading/repairing leads to disposal.

Storage Devices

• Secondary storage devices (not directly accessible by the CPU) store data, are non-volatile, and can be stored for any length of time that the user needs, even if it is for extended periods of time.
• These devices offer more storage than primary memory, but data access is slower than with RAM/ROM.

Magnetic Storage

• HDD stores data on computers, using magnetic platters spinning at ~7,000 rotations per second.
• Each platter has two surfaces that store data, while read-write heads move quickly to access the surfaces.
• Data is organized in sectors and tracks.
• HDDs are slower than RAM, and accessing data involves latency due to the movement of read-write heads.
• Over time, data on HDDs can becomes fragmented - which can be solved by defragmentation software organizing the existing data.

Solid State Storage

• SSDs (Solid State Drives) reduce latency vs. HDDs, because there are no moving parts, data can be retrieved more quickly.
• SSDs use NAND chips to store data, which controls electron movement in transistors.
• Some devices use EEPROM technology, which uses faster/more expensive byte-by-byte data access.

SSD vs HDD

• SSDs benefits over HDDs include:
• Higher reliability (no moving parts), lighter (ideal for laptops), faster data access, and lower power consumption (cooler operation).
• The drawback consists of longevity - write operations get rated for limited use, which makes them uncommon in servers, but improvements have been made. Additionally, memory of SSD is technology.

Optical Media

• CDs, DVDs, and Blu-ray Discs are optical storage devices using laser light to read/write data.
• CDs/DVDs use a thin layer of metal/dye to store data; they have a single spiral track from disc center outwards.
• When spinning, a laser moves along the track and reads the data; like HDDs, disc divides up information into sections to allow access easily.
• Data is stored on both CDs and DVDs in pits/bumps, red lasers are used to write, and write once R or rewriteable RW versions are both available.
• DVDs hold more data than CDs by using two layers, with a thin reflector between them, which allows the laser to read the second layer differently.

Input and Output Devices

• Feature: CD, DVD, Blu-ray
• Laser Wavelength:780 nm (red), 650 nm (red), 405 nm (blue)
• Storage Capacity: Lower, Larger than CD, 5 times larger than DVD Pit Size & Track Width: Larger, smaller pits and tracks, Much smaller pits and tracks
• Disc Construction: Single layer, Two 0.6mm thick layers, Single 1.1mm thick layer
• Birefringence Issues: None, possible due to two layers, None
• Encryption for Protection: No, No, yes to avoid piracy.

Printers

• Printers can come as laser, inkjet, and 3D.
• Laser printers use dry powder ink (toner) and static electricity to print text/images.
• Laser printers print the page at once, utilizing four toner cartridges for color: blue, cyan, magenta, and black.
• Black-and-white printers work similarly by using colored dots to make text/images.

Laser Printing Process

• The process of laser printing is as follows:
• Data from a document sends to a printer driver , an assessment confirms the chosen printer prints successfully (it is busy/offline), and confirms existing ink).
• The the data transfers to a temporary memory, the printer buffer.
• The printing drum receives a positive charge; rotating, a laser beam scans, removing the positive charge in negatively charged areas matching the printing text/images.
• Toner then coats the drum, attracting to the negatively charged parts due to its positive charge.
• Next, a negatively charged paper sheet is rolled over the drum, causing toner to stick, copying the image.
• Charge goes, then paper goes through fuser (heated rollers) that use heat to melt ink.
• The electrical charge, finally, goes from the drum from discharge map after printing.
• Inkjet printers work with heads that spray tiny droplets of ink onto paper. It has ink cartridges (a single cartridge), and a stepper motor with belt, and uses a paper feed to automatically load pages.

Printing Process

• Ink droplets print using two main methods. Thermal bubble: heat forms tiny bubbles, popping and pushing the ink onto the page.
• Piezoelectric: crystal vibrates when charged, forcing ink out and drawing in more for the next print.
• When using an inkjet printer to print, data sends from the computer driver, the driver has to transfer file formats chosen to the printer .
• A check goes to the driver to guarantee the ability for printing and data, transferring and creating a temporary memory; sheet of paper enters, sensor detects paper, and print text proceeds. .

3D printers

• 3D printers create solid objects by building them up with layers of powdered resin, metal, paper, or ceramic.
• 3D-printing uses additive manufacturing (builds layers) instead of subtractive (removing material) processes.
• Common 3D-printing methods include:
• direct 3D printing (uses inkjet tech and print heads)
• binder 3D printing (adds glue after each layer)
• newer methods using lasers/UV to harden liquid materials.

Speakers & Microphones

• Speakers convert digital sound into actual sound. To do this: The digital data goes through a DAC (Digital to Analogue Converter), making an electric current.
• Current goes through an amplifier so the DAC current is stronger.
• Current sends to a loudspeaker, creating sound.
• If sound enters a computer file, it can enter a (DAC), to then electric shock the loudspeaker.
• Wire coils wrap a iron core, creating a magnet with a current of electricity. A regular magnet remains places near the electromagnet.
• Field fluctuations cause the core to shift and resonate as the electric force fluctuates.
• Core links to cone-shaped parts (paper/plastic); the vibration then creates sound.
• Translate rate rate of DAC-output-voltages determines rate of analogue-voltages called the sampling-rate.
• Microphones go to computer, outside- or wireless-connection, via USB output, (CD) enhanced sound wave.

Microphones Operation

• Sound creates vibrations.
• Diaphragm records vibrations, the copper cables surround a magnetic , cone diaphragms, that create movement.
• Coil motion will damage magnets surrounding, electrical currents results.
• Current amplifies (analogously).

Screens

• Screens demonstrate output , which allows users to monitor , modern LEDs or OLED technology.
• OLEDs: carbon creates materials. When electricity outputs light, there is lack of backlighting, thinner.
• the screen consists of pixels, the blue green, that help the user see millions of colors.
• Finer pixel screens create image (ex: 1,6891-980 pixels - LCD vs OLED) for LCD and OLED pixel pictures:

Touch Screens

• Touch screens (input and output) use LCD/OLED tech, these are particularly in mobile phones and tablets.
• Capacitive is a glass layer device (the finger is special), with a good cost and good visibility; durability is also solid.
• Resistive relies heavily on finger - bare fingers - costs fall, but its output suffers, becoming vulnerable.
• VR : has many different functions (simulating nuclear fallout), repair/ testing.
• Headsets help video transfer via HDMI to the smart phone. (Eye-pictures use 3d lens, and use 110 degress to simulate 360 feild vision).

VR headset qualities

• Use rates 60-120 to look smooth and reliable and sensors on the LEDs simulate natural sensations that sound coming from multiple areas and eye movements.
• Sensors measure temperature, acidity and pressure/
• A clock is an example of constant fixed signals via movements. Since computers understand physical values need to be transferred to binary, the digital number for DAC outputs motor, also is a means for digital voltages and transfers to analog voltages. Actuator circuits link to the control systems, that open/close the circuits. Lastly a feedback response creates input and adjusts the process to a point.
• Sensors go into control applications to get data feedback, the subtle functions are explained to work on the computer.

Function applications

• Sensors send signals to the Microprocessor to get warnings and outputs, the signal will turn to digital signal and ADC
• (Microprocessor ( outside and inside) sensors send all the data.

Logic Gates

• Logic gates uses electronic circuits and (NOT, OR, AND, NAND, XOR, AND, and NOR).
• Logic circuits carry a functions, output value 0 or 1.

Truth tables

• Method outputs and inputs . Input combination, and outputs true vs false . They link circuits to Boolean Algrebra.

Electronic gates

• Used to help combine the function of all gates outputting the function true or false.
• (Not gate : is the input is not equal to 1), write NOT, and there are NOT outputs, and AND gates can be used with tables/ inputs. and so on.
• And so on by repeating the information about descriptions, output tables inputs output tables.
• And is written in both notation with the usage inputs. outputs. and a diagram.

This lesson explores fundamental concepts in computer hardware. Topics include analog to digital converters, display technologies like OLED and LCD, touch screen functionality, storage types (SSD, HDD), 3D printing, and embedded systems. It also covers digital logic circuits.