Netherlands VWO 5 Computer Science

Chapters: 2

1. Information

Goals of information processing · Identifying information · Representing data · Standard representations · Structured data

Data Representation: How Computers Store Numbers, Text, Images and Sound – Data is raw facts; information is data given meaning; knowledge is information we can use. A computer stores all data as bits (0 or 1). 8 bits make a byte, and 1 kB = 1000 bytes, 1 MB = 1000 kB, 1 GB = 1000 MB, 1 TB = 1000 GB. Numbers are stored in binary, where place values double: 1, 2, 4, 8 and so on. Text uses a character set: in ASCII 'A' is 65; Unicode covers every script. A bitmap image is a grid of pixels; size = width × height × colour depth. Sound is sampled: size = sample rate × bit depth × seconds. Vector images store shapes instead of pixels. Compression makes files smaller: lossless keeps every bit, lossy throws some detail away.
Data Structures: Arrays, Lists, Stacks, Queues and Trees – A data structure is a way of organising data in memory so a program can use it well. Arrays keep items in numbered boxes for instant access by index. Linked lists chain nodes with pointers, so inserting is easy. Stacks work last-in-first-out, queues first-in-first-out. Dictionaries find values by key, and trees store data in levels so searching is fast. Choosing the right structure makes programs faster and simpler.
SQL with MySQL: Create Tables, Change Rows and Ask Questions – SQL (Structured Query Language) is the language used to talk to a relational DBMS like MySQL. DDL commands (CREATE, ALTER, DROP) define tables; DML commands (INSERT, UPDATE, DELETE) change rows; DQL (SELECT) reads data. Each column has a data type such as INT, FLOAT, CHAR, VARCHAR or DATE. SELECT … WHERE filters rows using relational operators, BETWEEN, AND/OR/NOT and IS NULL.

2. Programming

Developing programs · Inspecting and adapting programs

Programming Basics: Sequence, Selection, Loops and Functions – A program is a set of exact instructions a computer follows. Every program is built from three structures: sequence (steps in order), selection (if/else choices) and iteration (loops). Variables store values. Functions group code into reusable, named blocks, which makes programs modular and easier to test, debug and maintain.