Data representation Study Guide

Computers need a standardised way to represent characters like letters, numbers, and symbols. 7-bit ASCII (American Standard Code for Information Interchange) is a character encoding standard that assigns a unique seven-bit binary code to 128 different characters. Each character, such as 'A', 'a', '1', or '!', corresponds to a specific numerical value, which is then stored as a 7-bit binary number. For example, the uppercase letter 'A' is assigned the decimal value 65, which converts to the binary representation 01000001. This standardisation ensures that text created on one computer can be correctly interpreted and displayed on another, regardless of their internal hardware or software configurations. The 7-bit nature means that each character uses exactly seven bits, allowing for 2^7 = 128 distinct codes. While 7-bit ASCII covers common English characters, numbers, and some control codes, it doesn't support characters from other languages or more extensive symbol sets, which led to the development of extensions like Extended ASCII (8-bit) and eventually Unicode.

Bitmap images are represented digitally as a grid of individual picture elements, known as pixels. Each pixel stores information about its colour. This colour information is converted into a binary code. The detail of how this works depends on the image's resolution and colour depth. Resolution refers to the total number of pixels in the image, typically expressed as width x height (e.g., 1920 x 1080 pixels). A higher resolution means more pixels, leading to a clearer image but also a larger file size. Colour depth specifies how many bits are used to represent the colour of each individual pixel. For instance, an 8-bit colour depth allows for 2^8 = 256 different colours, while a 24-bit colour depth (often called True Colour) allows for 2^24 = 16,777,216 distinct colours. A higher colour depth provides a more realistic and vibrant image but, again, increases the file size due to more data per pixel.