HS Computer Science · Unit 1 Summative Exam · Tue 6 Oct
Unit 1 cheat sheet
L1History of Computers
| Device | Who / when | Known for |
|---|---|---|
| Abacus | ancient | counting with beads |
| Napier's Bones | John Napier, 1617 | rods to multiply/divide |
| Pascaline | Blaise Pascal, 1642 | turning wheels — addition |
| Difference Engine | Charles Babbage, 1822 | producing tables |
| Punched cards | Hollerith & Powers, 1890 | US census |
| ENIAC | 1946 | first general-purpose electronic computer |
| UNIVAC | 1951 | first commercial computer |
Ada Lovelace — first programmer · Alan Turing — father of computer science.
L2Generations of Computers
| Gen | Years (class table) | Technology | Examples |
|---|---|---|---|
| 1 | 1942–1959 | Vacuum tubes | ENIAC, EDVAC, IBM 701 |
| 2 | 1959–1965 | Transistors | IBM 7030, CDC 1604, Honeywell 400 |
| 3 | 1965–1975 | Integrated circuits (ICs) | IBM 360/370, PDP-8/11 |
| 4 | 1975–1988 | Microprocessors (VLSI) | Apple II, Cray-1 |
| 5 | 1988–present | AI and quantum computing (ULSI) | PARAM, modern PCs |
Each generation: smaller, faster, more powerful (and cheaper). ICs = many transistors on one chip.
L3Types of Computers
| Type | Size · cost | Remember |
|---|---|---|
| Supercomputer | largest · most expensive | weather forecasting, space research, climate change, pandemics |
| Mainframe | large · expensive | thousands of users at once |
| Minicomputer | small · cheap | common in the 1970s, replaced by servers |
| Microcomputer | smallest · cheapest | the personal computer — what we carry |
L4Components: input & output
Input = data/signals into a computer: fingerprint scanner, facial recognition, motion sensors, VR gloves, voice assistants, mouse, microphone.
Output = information/results out: VR headsets, AR glasses, 3D printers (physical object from a digital model), haptic feedback (touch).
Both: touchscreen (shows output, takes touch input).
L5Software and its types
System software — runs and supports the computer: Operating System (Windows, Linux, macOS) · Utility Programs (antivirus, compression, file managers) · Device Drivers (printer, GPU).
Application software — helps users do tasks: Productivity (Word, spreadsheets) · Web & Communication (browsers, email, social media) · Graphics & Media (Photoshop, video editors) · Games & Entertainment · Custom (industry-specific).
Apps run on top of system software, which runs the hardware.
L6Memory and storage
Memory types: RAM, ROM, Cache, Flash. RAM is volatile — lost when power is off.
Memory ≠ storage. Local storage: hard disk, SSD, external drives. Cloud: Google Drive, Dropbox, iCloud.
Cloud ✓ access from multiple devices · ✗ needs internet, security & privacy (who can access student data, breaches).
L7Algorithms
| Word | Meaning |
|---|---|
| Algorithm | a sequence of instructions to solve a problem |
| Sequence | the order instructions are carried out |
| Input | data entering an algorithm |
| Process | something done to the data |
| Output | information produced by the algorithm |
| Trace | follow it step by step to see what happens |
| Debug | find and correct a problem |
Good algorithm: numbered steps · logical order · each step clear and specific · can be traced. Wrong order → it can fail.