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| Term | Definition |
|---|---|
| ASCII | The computer stores text using a number code. Every letter of the alphabet is given a code number. There are different codes for upper and lower case letters and the other characters on the keyboard such as punctuation. |
| Vector image | An image file that uses geometric shapes and coordinates to precisely define the parts of the image. Can be resized without pixelating and the file size will stay almost exactly the same. |
| Calculating colour depth | 2 to the power of the number of bits available. For example: 4 bit colour depth is equal to 2 to the power 4 which gives 16 different colours |
| Unicode | Inside the computer text characters are coded in digital form. Unicode is an international code used to represent text characters. |
| Byte | Inside the computer, on/off bits are organised into groups of 8. A group of 8 bits is called a "byte". |
| Bit | Binary numbers are made up of the digits 1 and 0. We abbreviate the term "binary digit" to "bit". |
| Debug | To debug means to find errors in software. |
| Nibble | A nibble is a group of 4 bits, or half a byte. |
| Hexadecimal | Hexadecimal is a number system based on 16. It has 16 digits. Each column-value is worth 16 times more than the previous column. |
| Data | Facts and figures of any kind are known as data. Facts and figures are stored inside the computer as binary data. |
| Bit rate | The number of bits used to store a second of sampled sound. Calculated by multiplying the sample rate by the bit depth. |
| Bit depth | The number of bits used to store each sound sample. |
| Sample rate | The number of times sound is sampled per second, measured in kHz. |
| Digital | A type of data that consists of a precise value that can be represented as a number. An example would be data stored as binary numbers. |
| Analogue | A type of data that varies continuously. |
| Lossless compression | A method of file compression where no data is lost in the compression process. The final file can be decompressed with all of its information intact. |
| Compression | A method of reducing the size of a file so that it takes up less storage space or bandwidth when it is transmitted. |
| Lossy compression | A method of file compression where data is permanently lost in the compression process. The final file will not contain all of the original information. |
| Effects of increasing colour depth | More bits per pixel results in a better quality image but also a larger file size |
| Height x Width x Colour Depth | Formula for estimating the file size of an image. |
| Metadata | Data about data. In the case of image files it is the data the computer needs to interpret the image data in the file, for example: resolution, colour depth and image dimensions. Can also include gps data, the date and camera information. |
| Resolution | The number of pixels per square inch. Also known as dpi. (dots per inch). The dpi determines the amount of detail the image has. |
| Colour depth | The number of bits used to represent the colour of a single pixel in a bit-mapped image. A higher number of bits gives a broader range of distinct colours. For example, an image stored as a .gif file uses 8 bits per pixel so the image could use 256 different colours. |
| .png .bmp .jpeg | Examples of bitmap file types. |
| Pixelate | Zooming in to an image so that the pixels are visible. |
| Pixel | Short for picture element. It is the smallest component of a bit-mapped image. |
| Bitmap image | An image that has been stored as a series of values per pixel. The colour of each individual pixel is stored in a file. |
| Denary/Decimal | Base 10 number system, how we normally count, uses the digits 0 to 9. |
| Binary | Base 2 number system, used by computers, uses the digits 1 & 0 only. |