1.2 Memory and Storage Flashcards
Features of Primary Storage
Very quick because accessed by CPU
Smaller in storage size
Includes RAM and ROM
Features of Secondary Storage
Slower because not directly accessed by CPU
Larger in storage size
Long-term storage because non-volatile
Includes optical, magnetic and solid state storage
Describe the features of RAM
RAM is volatile, and stores all currently running programs
Describe the features of ROM
ROM is non-volatile, read-only, and stores the bootstrap
What is virtual memory?
An extension of the hard disk drive (secondary storage) which stores programs when there is insufficient space in RAM
How does the use of virtual memory work?
If new data is needed to be stored in RAM, then unused data is moved to virtual memory to allow space in RAM.
If the unused data is required again, it can be moved back from VM to RAM.
What are the benefits of VM?
It allows more programs to be run with less system slowdown
What is an overflow error?
When a binary value is too large to be stored in the bits available
What is a character set?
A defined list of characters that are recognised and can be stored in a computer system.
How many bits are used to store a character in:
ASCII extended
Unicode
8 bits (1 byte) = max 256 characters
24 bits (3 bytes) = over 16 million characters
unicode is stored as 6 hex digits
Formula for calculating file size of a text file
bits per character x number of characters
What is color depth?
the number of bits used to represent a color
Formula for calculating file size of an image
resolution x color depth
Formula for calculating number of colors available
2 to the power of (color depth)
What is metadata?
Additional data about a file’s data
How are analogue waves converted to digital waves?
They are digitally recorded and stored in binary.
The amplitude of the analogue sound wave is measured and recorded in binary at specific intervals.
What is sample rate?
The number of times the amplitude of a sound wave is measured. (kHz)
What are the effects of higher sample rates on the file size?
Better audio quality since it more closely resembles an analogue wave.
Larger file sizes because more data is being stored
What is bit depth?
The number of bits used to store each sample.
What are the effects of higher bit depths on the file size?
Better audio quality since it more closely resembles an analogue wave.
Larger file sizes because more data is being stored
Formula for calculating sound file size
sample rate x bit depth x duration
What is compression?
To compress a file and make the size smaller
What are the benefits of compression?
Files:
take up less storage space (more files can be stored)
can be transferred/read from/written to quicker
How does lossy compression compress a file?
Permanently removes data undetectable to humans. This greatly reduces the size of the file without compromising the quality of the file too much.
How does lossless compression compress a file?
Reduces the size of a file without permanently removing any data. Therefore, the file is returned to its original form when decompressed, so no quality is lost.
What are the most suitable files for lossy/lossless compression to compress?
Lossy: videos/audio/photos
Lossless: executable files or word documents
