Learning Outcomes
What You Will Learn
Student Learning Outcomes (SLOs) as defined by FBISE for Unit 1.
Describe the five generations of computers and the technology behind each
Differentiate between natural and artificial systems with examples
Identify the core hardware components: input, output, system unit and storage devices
Explain the Von Neumann architecture: CPU, ALU, control unit, registers and buses
Understand data transmission and the memory hierarchy inside a computer
Differentiate volatile and non-volatile, and main and secondary memory
Distinguish system software, application software and programming languages
Identify the components, modes and devices used in data communication
Compare network types, topologies, and switching techniques
Explain the OSI model, common protocols, and how the Internet works
Computer Science Unit 1 — Complete Notes
Full chapter question bank with 253+ Q&A pairs and complete exercise solutions
History of Computing
Five Computer Generations
Each generation is defined by a major technological leap in how computers are built.
First Gen
1940 – 1956 · Vacuum Tubes
Slow, unreliable, huge and power-hungry. Programmed in machine language. Examples: ENIAC, UNIVAC I.
Second Gen
1956 – 1963 · Transistors
Smaller, faster, more reliable. Languages like FORTRAN, COBOL. Examples: UNIVAC II, IBM 7030.
Third Gen
1963 – 1971 · Integrated Circuits
Multiple transistors on one chip. Introduced keyboards & monitors. Example: IBM System/360.
Fourth Gen
1971 – Present · Microprocessors
LSI/VLSI chips, GUIs, portable devices. Example: Intel Pentium series.
Fifth Gen
Present & Beyond · AI & NLP
Learning, reasoning, parallel processing. Voice recognition, expert systems & robots.
Hardware
Core Hardware Components
A computer system is built from four essential categories of hardware.
Input Devices
Human → Computer
Keyboard, mouse, microphone, scanner, barcode reader, digital camera, touch screen.
System Unit
Motherboard + CPU
Houses the motherboard and microprocessor (ALU, Control Unit, Registers) — the "brain" of the PC.
Storage Devices
Hold Data & Programs
Hard disk, SSD, CD, DVD, memory card, USB flash drive — long-term or portable storage.
Output Devices
Computer → Human
Monitor, impact & non-impact printers, plotter, speakers — show processed results.
Computer Memory
The Memory Hierarchy
Memory is organized in layers that trade off speed for size — the fastest memory is also the smallest and most expensive.
Registers
Cache (L1 → L2 → L3)
Main Memory (RAM)
Secondary Storage (SSD / HDD / Optical)
↑ Faster & Smaller & CostlierLarger & Cheaper & Slower ↓
Memory Terminology
Memory Units
Each higher unit equals 1024 (2¹⁰) times the unit before it.
| Memory Unit | Power of 2 | Equivalent To |
|---|---|---|
| 1 Byte | 2³ bits | 8 Bits |
| 1 Kilobyte (KB) | 2¹⁰ Bytes | 1024 Bytes |
| 1 Megabyte (MB) | 2²⁰ Bytes | 1024 KB |
| 1 Gigabyte (GB) | 2³⁰ Bytes | 1024 MB |
| 1 Terabyte (TB) | 2⁴⁰ Bytes | 1024 GB |
| 1 Petabyte (PB) | 2⁵⁰ Bytes | 1024 TB |
| 1 Exabyte | 2⁶⁰ Bytes | 1024 PB |
PART 1
Hardware, Systems & Architecture
Computer Generations & Systems
1. What are the five generations of computers, and what technology defined each?
• Describe the evolution of computer generations.• Which technology characterized each generation of computers?
The first generation (1940–1956) used vacuum tubes; the second (1956–1963) used transistors; the third (1963–1971) used integrated circuits (ICs); the fourth (1971–present) uses microprocessors built with LSI/VLSI; and the fifth (present & beyond) focuses on artificial intelligence and natural language processing.
📝 Intel invented the world's first microprocessor, the Intel 4004, in November 1971.
2. What is the difference between natural and artificial systems?
• Define natural and artificial systems with examples.• How do natural and artificial systems differ?
Natural systems occur organically and are self-regulating, e.g., ecosystems, weather patterns, the human body. Artificial systems are human-designed to fulfil specific needs and require maintenance, e.g., communication networks, transportation systems, computers.
Von Neumann Architecture
3. What is Von Neumann Architecture, and what does it consist of?
• Who proposed Von Neumann Architecture, and when?• What is the stored-program concept?
Von Neumann Architecture, first published by John Von Neumann in 1945, is based on the stored-program concept — instructions and program data are stored in the same memory. Modern Von Neumann architecture consists of a CPU (Control Unit, ALU, Registers), a Memory Unit, buses, and Input/Output controllers.
4. What are the functions of the ALU, Control Unit, and Registers in a microprocessor?
• What does the ALU do?• What is the function of the Control Unit and registers?
The ALU (Arithmetic Logic Unit) performs arithmetic and logical operations. The Control Unit (CU) manages and directs all system activities, decoding instructions for the CPU. Registers are high-speed storage areas — all data must be stored in a register before it can be processed (e.g., MAR, MDR, AC, PC, CIR).
CPU = Control Unit + ALU + Registers + Cache
5. What are the three types of buses in a computer system?
• What does the address bus carry?• What is the function of the control bus?
A standard CPU system bus has three types: the address bus carries the addresses of data (not the data itself), the data bus carries the actual data between the processor, memory and I/O devices, and the control bus carries control signals to coordinate activities within the computer.
PART 2
Memory, Software & Programming Languages
Computer Memory
6. Differentiate between volatile and non-volatile memory.
• Give examples of volatile and non-volatile memory.• What happens to volatile memory when the power is off?
Volatile memory requires power to retain data and loses it when power is off, e.g., RAM, Cache, Registers. Non-volatile memory retains data even when power is off, e.g., ROM, Flash memory, HDDs.
⚠️ RAM is volatile and read/write; ROM is non-volatile and stores the BIOS that boots the computer.
7. What is cache memory, and how do L1, L2 and L3 differ?
• Why is cache memory needed?• Which cache level is the fastest?
Cache is a small, extremely fast memory between the CPU and RAM that stores frequently accessed data. L1 is inside the processor core (fastest, smallest); L2 is slightly larger and slower; L3 is shared among multiple cores and is the largest and slowest of the three.
Software & Programming Languages
8. What is the difference between system software and application software?
• Give examples of system software.• What are common types of application software?
System software manages and controls hardware, providing a platform for other software — e.g., the Operating System, device drivers, utilities, compilers. Application software performs specific tasks for users — e.g., productivity, business, entertainment and educational software.
9. Differentiate between low-level and high-level programming languages.
• What are machine language and assembly language?• Name the three categories of high-level languages.
Low-level languages (Machine & Assembly Language) are machine-oriented and close to the computer's architecture. High-level languages resemble English and are easier to learn — they are classified as Procedural (C, Pascal), Structured (FORTRAN, ALGOL), or Object-Oriented (Java, C++, Python).
📝 High-level programs need a compiler or interpreter to convert them into machine language for execution.
PART 3
Networking & Data Communication
Network Communication & Devices
10. What are the five basic components of network communication?
• What is a protocol, and why is it needed?• What is the role of the medium in data communication?
Network communication consists of five components: Sender (transmits the message), Message (the data itself), Medium (the path — wired or wireless), Protocol (rules governing communication), and Receiver (accepts the message).
⚠️ Without a protocol, two connected devices may not be able to communicate with each other at all.
11. How does a hub differ from a switch in a network?
• What is the function of a router and a gateway?• Why is a switch more efficient than a hub?
A hub broadcasts data to every connected device, making it simple but inefficient. A switch inspects packets and sends data only to the correct device, reducing traffic. A router connects networks and directs internet traffic, while a gateway connects networks using different protocols, acting as a translator.
OSI Model, Protocols & The Internet
12. What is the OSI model, and how many layers does it have?
• Who developed the OSI model, and when?• Name the seven OSI layers.
The OSI (Open Systems Interconnection) model, developed by the ISO in the 1970s, has seven layers: Application, Presentation, Session, Transport, Network, Data Link, and Physical — each performing a specific task during data communication.
13. What is the Internet, and how does it work?
• What was ARPANET?• What does DNS do?
The Internet is a global, decentralized network connecting billions of devices, evolving from ARPANET in the 1960s. It works through packet-switching — data is divided into packets routed via interconnected routers, while the DNS translates domain names into IP addresses.
📝 Common protocols: TCP/IP (internet communication), HTTP (web pages), FTP (file transfer), SMTP (email).
14. What is the difference between packet switching and circuit switching?
• Give an example of circuit switching.• Why are packets reassembled at the destination?
Packet switching divides data into small packets that travel independently and are reassembled at the destination, e.g., email. Circuit switching establishes one dedicated path for the whole session, e.g., a traditional phone call.
Network Design
Network Topologies
The arrangement of devices and connections within a network.
Bus Topology
All devices share one central cable. Cheap, but one break disables the network.
Star Topology
Every device connects to a central hub/switch. Easy to expand; hub failure is risky.
Ring Topology
Devices form a loop; data flows in one direction. Cost-effective but fragile.
Key Vocabulary
Unit 1 Vocabulary
Important terms — learn these definitions for exam questions.
| Term | Definition |
|---|---|
| Computer | A programmable electronic device that performs arithmetic and logical operations automatically using instructions |
| Vacuum Tube | Core technology of first-generation computers; large, slow and power-hungry |
| Transistor | Solid-state component that replaced vacuum tubes in second-generation computers |
| Integrated Circuit (IC) | A chip combining multiple transistors; defines the third generation of computers |
| Microprocessor (CPU) | The "brain" of the computer that executes instructions and performs calculations |
| System | A collection of interconnected components working together to achieve specific goals |
| Motherboard | The main circuit board containing the microprocessor, memory and connection slots |
| ALU | Arithmetic Logic Unit — performs arithmetic and logical operations |
| Control Unit (CU) | Directs and manages all CPU and system activities |
| Register | High-speed storage area inside the CPU that holds data during processing |
| RAM | Volatile read/write memory that temporarily stores data while the computer is on |
| ROM | Non-volatile memory that stores the BIOS and boot-up instructions |
| Cache Memory | Small, very fast memory between the CPU and RAM that stores frequently used data |
| Bit | The smallest unit of memory, representing a binary digit (0 or 1) |
| Byte | A group of 8 bits; the smallest unit of data a computer can process |
| System Software | Software that manages and controls hardware, e.g., the Operating System |
| Application Software | Software designed to perform specific tasks for users, e.g., MS Word |
| Compiler | Translates an entire high-level program into machine code before execution |
| Assembler | Converts assembly language into machine language |
| Low-Level Language | Machine-oriented programming language close to the computer's architecture |
| High-Level Language | User-friendly programming language that resembles English, e.g., Python, Java |
| Protocol | A set of rules that governs data communication between devices |
| Network Topology | The arrangement of devices and connections within a network (e.g., bus, star, ring) |
| LAN | Local Area Network — connects computers within a small area like a building |
| WAN | Wide Area Network — connects computers across large areas like countries |
| OSI Model | A seven-layer conceptual framework describing how networking protocols work together |
| Internet | A global network of interconnected computer networks |
Test Yourself: Unit 1 Quiz
Chapter-wise MCQs aligned with FBISE Federal Board syllabus. No login required. Instant results.
Start Quiz NowWant Live Explanation of Computer Systems?
Join W.H. Academy: Live tutoring, recorded lectures, and full chapter solutions for FBISE students in Rawalpindi and online across Pakistan.