1.2- Memory and Storage Flashcards
Secondary
This type of storage cannot be read directly by the CPU. It’s non-volatile and much bigger than primary. Examples are Hard Disk, USB Flash Drive, SSD, CD
Primary
This type of storage is also known as main memory or primary memory. It is volatile and can be accessed directly by the CPU
Random access memory
Primary Storage we can write to, also known as main memory. All data in use and instructions currently running are stored here. It is volatile.
Read only memory
Cannot be changed. Non-volatile semiconductor primary memory, contains the start-up instructions for the computer known as the BIOS
Volatile
Forgets all contents when powered off, RAM is this type
Non-volatile
Remembers all contents when powered off, ROM is this type
Write
We can do this to RAM but not ROM, it means change the contents
BIOS
The startup instructions for a computer, stored in ROM. It stands for Basic Input Output System
Virtual memory
Space in secondary storage that acts like extra RAM, so we can run more processes simultaneously
Process
Any part of a program that is currently running, this will need to be in primary memory so the CPU can execute it
Swapping
Moving a process from RAM to virtual memory to make more room in RAM for a new process
Thrashing
Constantly swapping processes between RAM and virtual memory because there is not enough RAM. Causes slow performance.
Running
Currently executing. (A process must be loaded in RAM before it can be executed)
Speed
How fast a secondary storage device can read and write data. SSDs and flash memory are fast
Durability
Ability of a device to withstand knocks and drops and still work, solid state devices are good
Reliability
How long a secondary storage device will last without breaking down or losing data, solid state devices are good at this
Cost
The price of a secondary storage device, SSDs are high
Portability
How easy it is to move a secondary storage device or its media around, CDs and memory sticks have this
Hard disk drive
High capacity magnetic secondary storage device. It has spinning platters so it wears out, making it less reliable and portable than SSD.
CD
Optical storage, a laser reads and writes the 700MB capacity optical disks. Disks are cheap and portable.
DVD
Optical storage, a laser reads and writes the 4.7GB capacity optical disks which are cheap and portable, but a bit more expensive than CDs.
Blu-ray disc
An optical storage component with a capacity of 25GB, a blue laser reads them, they are more expensive than DVDs but still cheap to make.
Solid state drive
No moving parts means this high capacity, fast, durable, low power and reliable secondary storage device is good for laptops but it’s expensive
Memory stick
A solid state storage removable storage device which is very portable, comes in capacities from 1GB up to 512GB
Memory card
A solid state storage device with a flat shape that is used in cameras and phones, also known as a flash card or SD card
Secondary storage
Non-volatile storage that stores programs and data. The OS, system software and application software are all installed here, plus files and folders. Comes in many types: magnetic, solid state and optical
Optical
A type of secondary storage that uses laser light to burn data onto a medium such as CD, DVD or Blu-Ray disc
Magnetic
This secondary storage type stores data by magnetising the surface, it includes hard disk drives and tape drives
Solid state
Secondary storage type with no moving parts, it uses semiconductor technology, and works by trapping electrons inside a gate. Includes SSDs, flash memory, memory sticks and SD cards
Capacity
The amount of data that can be stored in a storage device or on storage media. If you create lots of data you need this characteristic to be high
Speed
How fast data can be read from or written to a storage device. This characteristic is important if your application creates or uses a lot of data quickly such as a video
Binary
Data format that can be represented by electrical voltages, which can then be processed by logic gates in the computer
Decimal
Also known as denary, the numbers we use in everyday life, which cannot be processed by the computer
Encoding
Converting data into a binary format so that that it can be stored and processed. ASCII and JPEG are both examples
Logic gate
The basic building block of digital computers, it processes only 0s and 1s, which is why we use binary to encode all data
Capacity
The maximum number of bytes a storage device can hold. Usually measured in MB, GB, TB or PB.
File size
The size of a file in bytes, MB, GB etc. Adding up all the file sizes we want to store gives us the capacity we need
60
Number of MB needed to store 600 documents of average size 100KB
30
Number of MB needed to store 60 sound files of 500KB each
A videographer stores 500MB of video every day. Her hard drive has 40GB free. How many days until she needs to buy a new drive (or archive some files)?
80
A musician records a new song using 6.4MB every week. How many songs can she store on a USB memory stick with a capacity of 256MB?
40
A text file stores one character in every byte. A document contains 12,000 characters. If I make six copies, how many Kilobytes is that altogether?
72
A CCTV system records constantly to hard disk at a rate of 500MB every hour. To record a whole week of video before overwriting, how big must the hard drive be, in GB?
84
A school stores all student data on their server. An average student has around 200MB of files, and there are 1200 students in the school. Providing enough space for the current students, and then allowing for 50% growth, what capacity storage device is needed, in GB?
360
An SD card is labelled “32GB”. How many high-resolution photo files of size 25MB can it store?
1280
bit
A single binary digit (a zero or a one) written with a lower case b
nibble
A group of 4 binary digits or half a byte
Byte
A group of 8 binary digits or two nibbles, it can hold 256 unique values
Kilobyte
Full name of the unit that represents 1000 bytes
Megabyte
1000 Kilobytes, or 1 million bytes, its full name
Gigabyte
1000 Megabytes, or 1 billion bytes, the full name
Terabyte
1000 Gigabytes, or a million Megabytes, in full
Petabyte
1000 Terabytes, or a million Gigabytes, the long name
The number of bits in 8 bytes
64
The maximum number of different values we can store in a Byte
256
Number of KB in 0.5MB
500KB
Number of GB in a hard drive with a capacity of 2TB
2000GB
Number of bits in a text file of 1KB
8000
Number of bits in an image file of 3MB (write as “x million”)
24 million
Denary
The base 10 number system in which all numbers are made from 10 digits (0-9), also called decimal
Hexadecimal
The base 16 number system in which all numbers are made from 16 characters (0-9 and A-F)
Base
The number of digits used by a number system. This is 2 in binary and 10 in denary
Left shift
Moving the bits to the left. Multiplies a binary number by two.
Right shift
An operation that divides the binary number by two by moving the bits to the right.
Most significant bit
The leftmost bit of a binary number, it’s the column with the largest place value (128 in an 8-bit number)
Least significant bit
The furthest right bit in a binary number, in an integer it is the 1’s column.
ASCII
Character set using 7 bits to represent each character, giving 128 unique characters
Character set
A code that pairs each character from the alphabet with a unique binary number so we can store text in a computer, examples are ASCII and Unicode
Encoding
The process of converting data into a binary code so that a computer can process it
Unicode
Versatile character set using up to 32 bits so it can represent many more characters. The first 128 are the same as ASCII.
Number of bits in an ASCII code
7
Maximum number of bits in a Unicode representation
32
Total number of possible values in the ASCII character set
128
Number of bytes in a 32-bit Unicode value
4
File size
Using Unicode makes this bigger, because each character takes up more space
Bitmap
An image made of pixels, it blurs when scaled up, used for photos
Vector
An image made of curves, described by mathematical functions, it scales without blurring, used for logos
Pixel
A bitmap image is broken up into a grid of these, it’s short for “picture element”. Each one has a single colour which is encoded in binary.
Black and white
A image which is represented by the binary numbers 1 and 0 can only have these colours
The range of colours available with 8 bits of colour depth
256
Most JPEG images are encoded with this many bits of colour depth, giving us millions of colours
24
A colour bitmap image is made up of three colours, the initials are shortened to what 3 letter abbreviation?
RGB
Colour depth
The number of bits used to store the colour for each pixel, a higher number means more variety of colours
Resolution
The number of pixels in an image, higher value means a more detailed image
Metadata
Data added to an image file to encode its format, dimensions and colour depth
This goes up if we make the quality better by increasing the colour depth or resolution, meaning we need more storage
File size
Quality
Increasing the colour depth or resolution will make this better
