📊 Visual Reference · Years 7–9
Visual Diagrams
Every key diagram from Years 7 to 9 — binary tables, flowcharts, CPU architecture, network maps, database ERDs and more.
📘 YEAR 7 DIAGRAMS
Each bit position in an 8-bit binary number represents a power of 2. The place values double from right to left: 1, 2, 4, 8, 16, 32, 64, 128. To convert binary to denary, add only the values where you see a 1.
Green digits (1s) are the active bits — their place values get added together. Grey zeros are ignored.
Two conversion methods side by side: Binary → Denary (read place values) and Denary → Binary (divide by 2, read remainders upward).
LSB = Least Significant Bit (rightmost). MSB = Most Significant Bit (leftmost). Always use 8 digits, pad with leading zeros.
When data travels across the Internet it is broken into small chunks called packets. Every packet contains three sections — Header, Payload (data), and Footer.
The checksum in the footer lets the receiver detect if the packet was corrupted during transit. If so, it requests a retransmission.
Networks can be connected using physical cables (wired) or radio waves (wireless). Each has advantages and disadvantages in speed, reliability and mobility.
Schools typically use wired connections for desktops (reliability) and wireless for laptops and tablets (mobility).
Standard flowchart symbols: Oval = Start/End · Rectangle = Process · Diamond = Decision. Arrows show the direction of flow. Dashed arrows = loop back.
Every flowchart must have exactly one START and one END. Dashed arrows show loops back to earlier steps.
A flowchart with a counter variable — a common exam question. The user gets 3 attempts. If they fail all 3, the account is locked. This combines a loop and a counter.
The counter "attempts" is set to 0 before the loop starts. After each wrong try it increments. When it reaches 3 the loop exits and the account is locked.
The Internet is the global physical infrastructure of connected computers. The World Wide Web (WWW) is a service that runs ON TOP of the Internet — just one of many services, alongside email, file transfer (FTP) and video calls.
Tim Berners-Lee invented the World Wide Web in 1989. The Internet existed before the WWW. You access the WWW through a web browser using HTTP/HTTPS protocols.
Encryption scrambles data so only the intended recipient can read it. The original data is called plaintext. Encrypted data is called ciphertext. A key is needed to decrypt it.
HTTPS uses encryption so your passwords and card details are protected. The padlock icon in your browser means the connection is encrypted using TLS (Transport Layer Security).
Click each bit to toggle it on (1) or off (0). Watch the denary value update instantly. Try to make specific numbers — great for practising binary conversion before exams!
128
64
32
16
8
4
2
1
Denary Value
0
Binary
00000000
Hex
0x00
Try:
Binary uses base 2 — only 0s and 1s. Each bit position doubles in value from right to left (1, 2, 4, 8 … 128). To convert to denary: add up the place values where the bit is 1.
📗 YEAR 8 DIAGRAMS
A bitmap image is a grid of pixels. Each pixel stores a colour as a binary number. In 1-bit colour: 1 = black, 0 = white. This grid shows how the letter "A" is stored as rows of binary.
Blue = 1 (black pixel). Dark = 0 (white pixel). Formula: width × height × colour depth = file size in bits.
Colour depth is the number of bits used to store each pixel's colour. More bits = more colours available, but larger file size. Formula: number of colours = 2^(colour depth).
★ 24-bit "true colour" is the standard for digital photography. The human eye cannot distinguish more than ~10 million colours.
RLE replaces runs of repeated values with a count+value pair. It is lossless — no data is lost. Works best on images with large blocks of solid colour. Poor for photographs.
RLE is lossless — you can perfectly reconstruct the original. It is used inside PNG and TIFF file formats.
File size depends on three things: image width (pixels), image height (pixels), and colour depth (bits per pixel). Multiply them together and divide by 8 to get bytes.
This gives the UNCOMPRESSED file size. Formats like JPEG use lossy compression; PNG uses lossless compression. Both reduce the actual file size significantly below the raw calculation.
A spreadsheet grid — columns are lettered (A, B, C…), rows are numbered (1, 2, 3…). A cell reference combines them: B3 = column B, row 3. Formulas start with = and can use functions like SUM, AVERAGE, MAX, MIN, IF.
Green cells contain formulas (starting with =). Blue cells show summary/stats row. Cell references are relative by default — they update when copied.
Malware is malicious software designed to damage, disrupt or gain unauthorised access to computer systems. Different types work in different ways.
Most malware enters via email attachments, downloads, or infected USB drives. Never open attachments from unknown senders.
A topology is the layout pattern of how devices are connected in a network. Each has different advantages for reliability, cost, and speed.
Most modern schools and offices use Star topology because it is reliable — a single device failure doesn't take down the rest of the network. Bus was common in early Ethernet networks.
Every pixel's colour is stored as a binary number. Colour depth is the number of bits used per pixel. More bits = more possible colours = better quality but larger file size.
File size formula: Width × Height × Colour depth (bits) ÷ 8 = bytes. A 100×100 pixel 24-bit image = 100 × 100 × 24 ÷ 8 = 30,000 bytes = ~29KB before compression.
📕 YEAR 9 DIAGRAMS
The CPU continuously repeats the FDE cycle — millions of times per second. Every program instruction goes through all three stages. Clock speed (GHz) = how many cycles per second.
A 3 GHz CPU performs 3,000,000,000 FDE cycles every second. PC = Program Counter (stores address of next instruction).
The CPU contains specialist components. The Control Unit (CU) manages the FDE cycle. The ALU performs calculations. Registers are ultra-fast temporary storage inside the CPU itself.
RAM is volatile (data lost when power off). Storage is non-volatile (permanent). The CPU communicates with both via data, address and control buses.
Sound is an analogue (continuous) wave. To store it digitally, the wave is sampled at regular intervals. The sample rate determines how often (Hz). Bit depth determines how precisely each sample is recorded.
Stereo audio has 2 channels (left + right). CD: 44,100 × 16 × 60 × 2 = 84,672,000 bits ≈ 10.6 MiB per minute.
Bubble sort compares adjacent pairs and swaps them if they are in the wrong order. After each full pass, the largest unsorted value "bubbles" to its final position at the end.
Bubble sort requires at most n−1 passes for n items. Maximum comparisons = n(n−1)/2. It is simple but inefficient for large lists.
Linear search checks each element one by one from the start. It works on any list — sorted or unsorted. Best case: 1 comparison (target is first). Worst case: n comparisons (last or not found).
Red boxes = checked but not target. Green box = found. Grey boxes = never checked (search stopped when found).
A relational database stores data in linked tables. A Primary Key (PK) uniquely identifies each record. A Foreign Key (FK) in one table links to the PK in another table, creating a relationship.
StudentID = "001", "002" — unique for each student. ClassID in Students matches ClassID in Classes — this is a one-to-many relationship.
Networks are classified by their geographic range. PAN covers a few metres, LAN covers a single building or campus, and WAN spans large distances using third-party infrastructure.
The Internet is the world's largest WAN. A school LAN might be connected to the Internet (WAN) via a router provided by an ISP.
An HTML document has a tree-like structure called the DOM (Document Object Model). Every element is a node. Parent elements contain child elements. The root is always <html>.
Every HTML element is a node in the tree. <html> is the root. <head> and <body> are its two direct children. Indentation in code mirrors this tree structure.
The bubble sort algorithm as a formal flowchart — the type you need to be able to draw and interpret in the exam. Shows nested loops (inner loop inside outer loop) and the swap operation.
This is the complete bubble sort flowchart showing two nested loops. The outer loop counts passes; the inner loop does the comparisons and swaps within each pass.
A storage device is the hardware that reads and writes data (e.g. the hard drive unit). Storage media is the physical material that actually holds the data (e.g. the magnetic disk inside). Some devices and media are the same object (USB stick), others are separate (DVD drive + DVD disc).
SSDs (Solid State Drives) have no moving parts — they're faster, quieter, and more durable than HDDs. HDDs are cheaper per GB and better for large backups. RAM is volatile primary storage — it loses everything when power is cut.
Programming languages range from high-level (human-readable, like Python) to low-level (machine-level, like Assembly and Machine Code). Translators convert high-level code to machine code so the CPU can execute it.
Python is an interpreted high-level language — easy to read and write but slower than compiled languages like C++. Machine code runs directly on the CPU with no translation needed.
Step through a bubble sort pass-by-pass. Watch the algorithm compare adjacent pairs and swap them when out of order. The largest values "bubble" to the end each pass.
Comparing
Sorted
Swapped
Bubble sort has O(n²) time complexity — slow for large lists. Best case: O(n) if already sorted. It is simple to understand and implement, making it ideal for learning algorithm concepts.
Enter a target value and see both algorithms search simultaneously. Linear search checks one-by-one from the start. Binary search halves the list each time — much faster on sorted data.
Target must be in 1–99 range
Linear Search
Binary Search
Binary search requires a sorted list. For a list of 1000 items: linear search needs up to 1000 checks, binary search needs at most 10 (log₂1000 ≈ 10). This is why sorting data first pays off.