Hardware Flashcards
Describe three differences between RAM and ROM.
RAM
• loses contents when power turned off/volatile memory/temporary memory
• stores files/data/operating system currently in use
• data can be altered/deleted/read from and written to
• memory size is often larger than ROM
ROM
• doesn’t lose contents when power turned off/non-volatile memory/permanent memory
• cannot be changed/altered/deleted/read only
• can be used to store BIOS/bootstrap
DVD-RAM and flash memory are two examples of storage devices.
Describe two differences in how they operate.
DVD-RAM
• data is stored/written using lasers/optical media
• DVD-RAM uses phase changing recording, in which varying laser intensities cause
targeted areas in the phase change recording layer to alternate between an amorphous
and a crystalline state.
• uses a rotating disk with concentric tracks
• allows read and write operation to occur simultaneously
flash memory
• most are NAND-based flash memory
• there are no moving parts
• uses a grid of columns and rows that has two transistors at each intersection
• one transistor is called a floating gate
• the second transistor is called the control gate
• memory cells store voltages which can represent either a 0 or a 1
• essentially the movement of electrons is controlled to read/write
• not possible to over-write existing data; it is necessary to first erase the old data then
write the new data in the same location
State three differences between Dynamic RAM (DRAM) and Static RAM (SRAM).
• DRAM has to be refreshed / charged
// SRAM does not request a refresh
• DRAM uses a single transistor and capacitor
// SRAM uses more than one transistor to form a memory cell
// SRAM has more complex circuitry
• DRAM stores each bit as a charge
// SRAM each bit is stored using a flip-flop / latch
• DRAM uses higher power( because it requires more circuitry for refreshing)
// SRAM uses less power (no need to refresh)
• DRAM less expensive (to purchase / requires fewer transistors )
// SRAM is more expensive (to buy as it requires more transistors)
• DRAM has slower access time / speed (because it needs to be refreshed)
// SRAM has faster access times
• DRAM can have higher storage / bit / data density
// SRAM has lower storage / bit / data density
• DRAM used in main memory
// SRAM used in cache memory
State the purpose of the double brackets.
The contents of the MAR is an address, it is the contents of that address
which is transferred to MDR
• The contents of the address pointed to by the MAR is transferred to the
MDR
State what is meant by an interrup
A signal from a source / device
• Telling the processor its attention is needed
Describe the internal operation of a microphone.
The microphone has a diaphragm / ribbon (accept equivalent)
• The incoming sound waves cause vibrations (of the diaphragm)
• «causing a coil to move past a magnet (dynamic microphone) //
changing the capacitance (condenser microphone) // deforms the
crystal (crystal microphone) etc.
• An electrical signal is produced
Describe the internal operation of a laser printer.
The revolving drum is initially given an electrical charge
• A laser beam (bounces off moving mirrors) scans back and forth across
the drum
• …discharging certain points (i.e. ‘drawing’ the letters and images to be
printed as a pattern of electrical charges)
• The drum is coated with oppositely charged toner (which only sticks to
charged areas)
• The drum rolls over electro-statically charged paper // Electro-statically
charged paper is fed (towards the drum)
• The ‘pattern’ on the drum is transferred to the paper
• The paper is passed through the fuser to seal the image
• The electrical charge is removed from the drum // the excess toner is
collected
Describe progressive encoding.
Stores all the scan lines for an entire frame // displays / records all the
frame data at the same time // not split into fields
• Complete frames are displayed in sequence
• The rate of picture display is the same as the frame rate.
Define the term copyright.
Formal or legal recognition of ownership of the program // Formal or legal
restriction / permissions on use of the program // The intellectual property
rights to the program
Explain why Shazia does not want to use an open source licence
She does not wish to release the source code
• She does not want anyone to be able to edit / modify / share the source
code/program
• She wants to make money from the program
Explain why Shazia does not want to use an open source licence.
Commercial Software
• The program is purchased for a fee
• It restricts the number of users/possible time period for use // Limited
number of installations allowed // Software key needed to install
• Source code not provided // source code protected / cannot be edited
• Anyone can purchase/download if agree to the terms
Shareware
• The program is free for a trial period // The (free) program may have
limited functionality // Need to purchase / enter details after trial
• Users do not have access to the source code // source code may not be
edited
• Users may re-distribute the software.
Freeware
• There is no charge for the software
• The software could still be copyrighted
• She can set her own restrictions on what a user can do with the
program
Give one reason why the tablet computer needs secondary storage.
To store files / software long term
Describe solid state memory.
No moving parts
• Solid state memory is non-volatile
• Makes use of blocks / arrays of
• « Semiconductors // NAND gates // NOR gates // transistors // integrated
circuits
• SSD Controller manages the components
• Uses a grid of columns and rows that has two transistors at each intersection
• One transistor is called a floating gate
• The second transistor is called the control gate
• Memory cells store voltages which can represent either a 0 or a 1
• Essentially the movement of electrons is controlled to read/write
• Not possible to overwrite existing data // it is necessary to first erase the old
data then write the new data in the same location
State the purpose of RAM and ROM memory in the computer.
RAM stores currently running parts of files / programs / processes / OS
• ROM stores boot up instructions / OS kernel // data permanently // store the
firmware for the tablet
Describe how the images and sound are encoded into a digital form
Images
• The images are stored as bitmaps
• Each image is made up of pixels
• « each pixel is of a single colour
• Each colour has a unique binary number
• Store the sequence of binary numbers for each image / frame // store the
binary value of each pixel
Sound
• Measure the height/amplitude of the sound wave
• A set number of times per second // at regular time intervals
• Each amplitude has a unique binary number
• Store the sequence of binary numbers for each sample
