1.2 Memory and Storage Flashcards
Primary storage
RAM and ROM, holds data and instructions which the CPU can access more easily and quickly than from secondary storage.
RAM
Random Access Memory. Volatile and read/write. Is a temporary store for instructions and data currently in use.
ROM
Read Only Memory. Non-volatile and read only. Stores the instructions for starting up the computer, BIOS tests and loading the operating system into RAM.
Virtual memory
Using part of the hard disk as if it were RAM. It allows more applications to be open than RAM can store.
Secondary storage
Permanent storage of instructions and data not in use by the processor. Stores the operating system, applications and data not in use. Read/write and non-volatile.
Optical storage
CD/R, CD/RW, DVD/R, DVD/RW. Used to store music, films and archive files. Low capacity, slow access speed, high portability, low cost and prone to scratches.
Magnetic storage
Hard disk drive. Stores operating system and applications. High capacity, medium data access speed, low portability, reliable but not durable and low cost.
Solid state storage
Memory cards and solid state hard drive. Used in digital cameras and smart phones. Medium capacity, high portability, reliable and durable, no moving parts, fast access speeds and high cost.
Storage capacity
The amount of data a storage device is able to store.
Storage speed
The read/write access speed of a storage device.
Storage portability
How easy it is to transport a given storage medium.
Storage durability
How resistant to damage and wear and tear a storage device is. Devices with low durability will wear out easily over time.
Storage reliability
How likely a storage device is to correctly write, read, delete and modify data.
Storage cost
The relative price of a storage device.
Bit
The smallest unit of storage in a computer system, represented either by a binary 1 or 0.
Nibble
Half a byte or 4 bits.
Byte
8 bits.
Kilobyte
1000 (1024) bytes.
Megabyte
1000 (1024) kilobytes.
Gigabyte
1000 (1024) megabytes.
Terabyte
1000 (1024) gigabytes.
Petabyte
1000 (1024) terabytes.
Denary
A numerical system of notation that uses 10 as its base. The 10 decimal base digits are 0-9.
Binary
A numerical system in which there are only two possible values for each digit: 0 and 1.
Binary arithmetic
The process of adding two or more positive 8 bit binary numbers.
Overflow
A number that’s too large to be represented by the device meant to store it.
Hexadecimal
A numerical system that uses 16 rather than 10 as its base.
Binary shifts
Allows you to easily multiply and divide binary numbers. A left shift multiplies by 2 and a right shift divides by 2.
Character set
A set of symbols that may be represented by a computer. These symbols, called characters, can be letters, digits, spaces or punctuation marks, the set includes control characters.
ASCII
America Standard Code for Information Interchange. A character set used for early telecommunication systems. ASCII codes use 7 bits. Extended ASCII uses 8 bits.
Unicode
Standard character set that replaces the need for all different character sets. It incorporates characters from almost all the world’s languages, including emojis. It is a 16-bit extension of ASCII.
Pixel
A pixel is the smallest unit of a bitmap image, it is represented by a square on a compute monitor display screen.
Metadata
Data about data.
Colour depth
Also known as bit depth. Th number of bits used to indicate the colour of a single pixel.
Resolution
The number of pixels contained on a display monitor, expressed in terms of the number of pixels on the horizontal axis and the vertical axis.
Image quality
The overall detail of the image, affected by colour depth and resolution.
Image file size
The file size of an image. Calculated by: colour depth x image height x image width.
Sample rate
The number of samples taken per second, measured in Hertz.
Sample duration
How may seconds of audio the sound file contains.
Sample bit depth
The number of bits used to store each sample.
Playback quality
The finished quality of the digital sound file, affected by the sample rate and bit depth.
Sound file size
The overall size of a sound file, calculated by: sample rate x duration x bit depth.
Compression
Reducing the size of a file.
Lossy compression
Reducing file size by losing data irreversibly in parts of a file that are least noticeable.
Lossless compression
Reducing the file size but no data is lost, the original file can be accessed.
