memory and storage

• Primary Storage

  Also known as memory. Holds the data, programs and instructions currently in use.
• RAM

  Random Access Memory. Stores programs and data before they are processed by the CPU. Read/write memory, meaning the contents can be changed. The contents are lost when the computer is turned off.
• ROM

  Read Only Memory. Data can be retrieved but not changed and the contents are not lost when the computer is turned off. Used to store programs for embedded system
• Volatile Memory

  Data stored in volatile memory is lost when the computer is turned off.
• No-Volatile Memory

  Data stored in non-volatile memory is not lost when the computer is turned off.
• Virtual Memory

  Space on the computer's hard drive used as main memory (RAM). Virtual memory is slower than main memory.
• Optical Storage

  A type of secondary storage which stores data on a spinning plastic or metal disk. Data is read from and written to the disk using a laser.
• Magnetic Storage

  A type of secondary storage which uses magnetic fields to store data. A read/write head reads and writes data from the media.
• Solid State Storage

  A type of secondary storage which uses flash memory to store data. They have no moving parts and are much faster than optical or magnetic storage.
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  HDD (Hard Disk Drive)

  A magnetic storage drive which can store large amounts of data and is often the main method of secondary storage in personal computers. The drive contains a number of internal disks and a read/write head used to read and write data.
• DVD (Digital Versatile Disk)

  A high capacity optical storage disk commonly used for video storage. A range of capacities are available up to 17GB
• CD (Compact Disk)

  An optical storage disk often used to store music. Capacity is usually around 800mb
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  SSD (Solid State Drive)

  A solid state storage drive which carries out the function of a traditional HDD. They are much faster than HDDs and less easy to damage as they have no moving parts. They are also more expensive and usually lower capacity.
• Bit

  The smallest unit of storage, containing a binary 1 or 0.
• Binary

  A number system used by computers. It contains only two symbols, 0 and 1 and is also known as base 2.
• Denary

  The number system most often used by people. It uses the digits 0 to 9 and is also known as base 10 or decimal.
• Overflow Error

  This happens when not enough space has been allocated to store the results of a calculation. For example, if one byte has been allocated but the result is 9 bits long.
• Hexadecimal

  A number system used by computers. It contains only two symbols, 0 and 1 and is also known as base 2.
• Binary Shift

  A process used to preform maths on binary numbers. It involves moving all the digits to the left or right.
• Most Significant Bit

  The furthest left digit in a string of binary numbers, its position means it has the highest value.
• Least Significant Bit

  The furthest right digit in a string of binary numbers, its position means it has the lowest value.
• Character

  A single symbol, for example a letter, number or punctuation mark.
• Character Set

  A system for representing characters in binary, each character is assigned a unique binary number.
• ASCII

  American Standard Code for Information Interchange. A 7 bit character set used to represent characters.
• Unicode

  A much larger character set created to overcome the limited number of characters available in ASCII. It includes many different language

  characters as well as other symbols such emojis.
• Pixel

  Short for Picture Element. Pictures on a computer are divided into a grid, with each square in the grid being one pixel which can be a single colour.
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  Metadata

  Additional data about a file such as when it was created or who created it. Commonly used with photos to store things like the make of camera or location the photo was taken.
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  Colour Depth

  The amount of bits available for colours in an image. The higher the

  colour depth the more colours available and therefore the more realistic the image will appear.
• Resolution

  The number of pixels an image is divided into. The higher the resolution, the more pixels in the image and the clearer it will be.
• Sample Rate

  The number of samples taken in one second. This is measured in hertz (Hz), 1Hz is one sample per second. The higher the sample rate, the more samples per second and therefore the higher the quality of the file.
• Bit Depth

  The number of bits available for each sample. The higher the bit depth, the more bits available and therefore the better the quality.
• Analogue

  A continuously varying signal, usually represented as a curved line. Examples include sound or temperature recordings.
• Compression

  A way of reducing the size of a file. It is often used with photos, music and video files.
• Lossy Compression

  A compression method which reduces the file size by removing certain data. The original file cannot be restored from the compressed version but the file is reduced by more than with lossless compression.
• Lossless Compression

  A compression method which reduces the file size without losing any data. The original file can be restored from the compressed version, but the file size is not reduced by as much.