WJEC GCSE Digital Technology

Study Notes

GCSE Digital Technology: Data Types and Storage Mediums

Analogue data is continuous and changes smoothly, while digital data is discrete and made up of binary digits (bits).
Computers can only process digital data, so analogue data needs to be converted before it can be used by a computer.
Examples of analogue devices include clocks and thermometers, while digital devices include smartphones and digital cameras.
Bits are the smallest pieces of data that a computer can process/store, and all information processed by a computer is in the form of a sequence of 1s and 0s.
Different storage mediums include magnetic storage (e.g. computer hard-drives), optical storage (e.g. DVDs), solid-state storage (e.g. USBs), and cloud storage (e.g. Google Drive).
Magnetic storage is low cost per gigabyte and has large capacity, but is less portable and less rugged than other storage types.
Optical storage is cheap for small amounts of storage, portable, and not affected by magnetic fields, but slow to write and easily scratched.
Solid-state storage is faster than hard disks, large capacity, and very tough and rugged, but expensive and easily lost/stolen.
Cloud storage offers remote backup and access from anywhere with a network connection, but relies on a reliable network connection and costs money to store data.
Digital sound needs to be converted from analogue to digital before it can be processed by a computer, using an analogue to digital converter (ADC).
Digital images can be stored as bitmap images (made up of pixels) or vector images (made up of mathematical equations), and can be compressed to save space.
Compression techniques for digital sound and images can reduce file size without significantly affecting quality, using methods such as lossy compression (removing data) or lossless compression (reducing redundancy).Digital Sound and Images
Digital sound is produced by converting analogue sound into digital data using a process called analogue to digital conversion (ADC).
Digital sound can be edited on a computer and then converted back into analogue sound using digital to analogue conversion (DAC).
The quality of digital sound depends on the sample rate (number of samples per second) and bit depth (number of bits available for each sample).
Uncompressed digital sound files have higher quality but larger file sizes compared to compressed digital sound files.
Compressed digital sound files use lossy compression, which permanently removes data to reduce file size and can result in lower quality sound.
Bitmap images are made up of pixels and have higher file sizes compared to vector images, which are made up of mathematical calculations.
Image resolution is determined by the number of pixels displayed horizontally and vertically, with higher resolution images having sharper quality but larger file sizes.
Vector images are scalable, meaning they can be enlarged without losing quality, while bitmap images can become pixelated when enlarged.
Image compression can be lossless or lossy, with lossless compression maintaining image quality but still reducing file size, and lossy compression permanently removing data to reduce file size.
PNG is a popular lossless compression type for graphics that might need to be edited, while JPEG and GIF are popular lossy compression types for digital camera images and simple animated images, respectively.
Storing uncompressed digital sound and high resolution bitmap images require more storage space compared to compressed digital sound and low resolution images, respectively.
Different file types for digital sound and images have different effects on overall sound and image quality as well as file size, and users can choose between them based on their preferences and needs.