data storage and compression

A bit is the smallest unit of data storage, representing a single binary digit (either 1 or 0.)

A byte is 8 bits.

A kibibyte is 1024 bytes (2^10 bytes).

A megabyte is bytes, while a mebibyte is bytes.

False. When converting between units larger than a byte, we use multiples of 1024 (2^10).

To convert from bytes to bits, multiply by 8.

A tebibyte is 1,099,511,626,776 bytes (2^40 bytes).

The symbol for mebibyte is MiB.

False. A nibble is 4 bits.

To convert from kibibytes to bytes, multiply by 1024.

The size of a bitmap image is calculated by: Resolution x colour depth or Image width x image height x colour depth

Resolution is the total number of pixels in an image, calculated by multiplying the image width by the image height.

Colour depth is the number of bits used to represent the colour of each pixel.

True. A colour depth of 24 bits is equal to 3 bytes.

The size of a sound file is calculated by Sample rate x duration x sample resolution.

Sample rate is the number of samples taken per second in a digital audio recording.

Sample resolution is the number of bits stored per sample in a digital audio recording.

To convert file size from bits to bytes, divide by 8.

To convert file size from bytes to kibibytes, divide by 1024.

False. The resolution of an image is measured in pixels (width x height).

Compression is reducing the size of a file so that it takes up less space on secondary storage.

Three benefits of compression are:

Lossy compression is a method of data compression where data is lost in order to reduce file size, resulting in a loss of quality but smaller file sizes.

Lossless compression is a method of data compression where data is encoded to reduce file size without losing any information, allowing the original data to be perfectly reconstructed.

False. Lossy compression is irreversible.

Files suitable for lossy compression are those where reducing quality is acceptable, such as images, video, and sound files.

In photographs, lossy compression tries to group similar colours together, reducing the number of colours in the image without significantly compromising the overall visual quality.

True. Lossless compression can be used on all types of data.

In documents, lossless compression uses algorithms to analyse the contents, looking for patterns and repetition, such as replacing repeating characters with a single character and the number of occurrences.

An advantage of lossless compression is that the file can be returned to its original state without any loss of data quality.