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| Pregunta | Respuesta |
| 3 main types of secondary storage | ○Magnetic hard disk ○ Solid State (flash) memory ○ Optical discs |
| What are optical disks and explain briefly how they function. | Consists of one continuous spiral track on its surface. A laser head will read the "pits" and "lands" on the disk surface. Pits=0 due to little reflection, lands=1 due to the reflection when read. Writable disks use photosensitive dye that turn opaque when laser are directed at them and reflects light |
| What are solid state drives and how do they work? | They're made of semi-conductors but don’t lose data when machine turns off, they're programmable ROM chips, so they're more of a drive than a disk. Uses NAND memory that organizes data into blocks, similar to older hard disks blocks are data that are grouped into fixed bytes. These blocks are managed by controllers. Blocks are allocated on semiconductors, which takes up little space, therefore when adding or deleted data the access time becomes fast. |
| What are magnetic hard disks and how do they work? | Actually made of many disks stacked into a pile and stores data magnetically. Changes in magnetism represents 0s and 1s . These disks spin and are attached to a read and write head connected to an actuator arm. Each disk is split into tracks that are also split into sectors which can be read by the OS. Disks' surfaces contain a film of magnetised metal grains that is placed in a magnetic field of an electromagnet that can change the magnetic direction of the metal grains. The reader then converts the grains magnetic direction into binary. |
| Briefly, how do inkjet printers work? | 1. Roller feeds paper 2. Printhead containing nozzles drip picolitres of ink onto sheet while being moved horizontally on a stabiliser belt 3. Roller is synchronised to move the sheet vertically forward in time with the dripping of the ink |
| Briefly, how do laser printer work? | 1. Rotating drum inside paper is filled with a charge-holding chemical 2. A laser beam is reflected and hits the drum and discharges the positive charges on the drum and the remaining negative charges creates an "image" to match what is to be printed 3. While the drum rotates, a positively charged toner (powdered ink) nearby is attracted to the drum's remaining neg. charge 4. As paper is passed through it is negatively charged and so the positively charged toner is attracted to the paper, away from the drum 5. A fuser (heated rollers) finally fuses the toner by melting the toner ink onto the paper surface. A discharge lamp then removes the charge from the drum for the next print queue |
| Why do we need Secondary storage? | RAM is volatile, cant hold data for long Storage on ROM and RAM is small Assembling and removing RAM isnt very practical and convenient at times |
| Why do we need RAM and ROM | RAM: Reads and writes temp. data during runtime, can be randomly accessed so it's quick ROM is needed for booting programs on the computer and to store important read-only system files |
| What is SRAM | Static RAM SRAM: Volatile when power is turned off, but less volatile than DRAM Faster and more expensive than DRAM, hence higher access time, because it has lots of logic gates Typically used for CPU cache and registers Cannot refresh programmes Lower storage capacity than DRAM Requires 6-8 transistors |
| What is DRAM | Needs to be constantly refreshed or contents will be lost (very volatile), transistors lose charge very easily Uses less power than SRAM and is cheaper, therefore slower access time Typically used for main memory in PCs Memory can be deleted and refreshed in a programme Higher storage capacity, today's standard is 4-8GB Requires 3 or 4 transistors |
| What do XOR gates do? | Only outputs 1 when either A or B (but not both) are 1 |
| What are the symbols for the gates and their functions? |
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