Unit 2: The Computer System Hardware Notes | BSc CSIT 1st Semester IIT
Complete and detailed notes for BSc CSIT 1st Semester students of Nepal on Unit 2: The Computer System Hardware according to IIT syllabus. This study material covers CPU, Memory Unit, Instruction Format, Instruction Set, Instruction Cycle, Microprocessor, Interconnecting Units of Computer, and Inside a Computer Cabinet.
Introduction to Computer Hardware
Computer hardware refers to all physical parts of a computer system that can be seen and touched. Hardware components work together to input data, process information, store results, and generate output.
Main units of a computer system:
- Input Unit
- Central Processing Unit (CPU)
- Memory Unit
- Output Unit
- Storage Devices
1. Central Processing Unit (CPU)
The Central Processing Unit (CPU) is known as the brain of the computer. It controls all operations and performs processing tasks.
Main Components of CPU
a. Arithmetic Logic Unit (ALU)
- Performs arithmetic operations like addition, subtraction, multiplication, division
- Performs logical operations like AND, OR, NOT, comparison
b. Control Unit (CU)
- Controls and coordinates all activities of the computer
- Fetches instructions from memory
- Decodes instructions
- Controls execution process
c. Registers
Registers are very small and fast memory locations inside CPU used for temporary storage.
- Program Counter (PC)
- Instruction Register (IR)
- Memory Address Register (MAR)
- Memory Data Register (MDR)
CPU Performance Depends On
- Clock Speed
- Number of Cores
- Cache Memory
- Processor Architecture
2. Memory Unit
Memory unit stores data, instructions, and results. It is essential for proper functioning of the computer.
Types of Memory
A. Primary Memory
i. RAM (Random Access Memory)
- Temporary memory
- Volatile memory
- Data lost when power is off
ii. ROM (Read Only Memory)
- Permanent memory
- Non-volatile
- Stores BIOS and firmware
B. Secondary Memory
- Hard Disk Drive (HDD)
- Solid State Drive (SSD)
- Pen Drive
- Memory Card
- CD/DVD
Memory Hierarchy
Registers → Cache → RAM → SSD/HDD → Optical Storage
Memory Units
- 1 Bit = Binary digit
- 8 Bits = 1 Byte
- 1024 Bytes = 1 KB
- 1024 KB = 1 MB
- 1024 MB = 1 GB
- 1024 GB = 1 TB
3. Instruction Format
Instruction format means the arrangement of bits in an instruction. It tells CPU what operation to perform.
Main Parts of Instruction
- Opcode = Operation code
- Operand = Data or memory address
Example:
ADD A, B
ADD = Opcode
A, B = Operands
Types of Instruction Format
- Zero Address Instruction
- One Address Instruction
- Two Address Instruction
- Three Address Instruction
4. Instruction Set
Instruction set is the collection of all instructions that a processor can understand and execute.
Categories of Instruction Set
a. Data Transfer Instructions
- MOV
- LOAD
- STORE
b. Arithmetic Instructions
- ADD
- SUB
- MUL
- DIV
c. Logical Instructions
- AND
- OR
- NOT
- XOR
d. Branching Instructions
- JUMP
- CALL
- RETURN
e. Input / Output Instructions
- IN
- OUT
5. Instruction Cycle
Instruction cycle is the step-by-step process followed by CPU to execute instructions.
- Fetch Instruction
- Decode Instruction
- Execute Instruction
- Store Result
This cycle repeats continuously while computer is running.
6. Microprocessor
A microprocessor is a programmable integrated circuit containing CPU functions on a single chip.
Features of Microprocessor
- Small size
- High speed
- Low cost
- Reliable
- Low power consumption
Examples
- Intel Core i3
- Intel Core i5
- Intel Core i7
- AMD Ryzen
Applications
- Computers
- Mobile Phones
- ATMs
- Cars
- Robots
7. Interconnecting the Units of a Computer
Different units of computer communicate through buses.
What is Bus?
Bus is a communication pathway used to transfer data, addresses, and control signals.
Types of Bus
- Data Bus – Transfers data
- Address Bus – Transfers memory addresses
- Control Bus – Transfers control signals
8. Inside a Computer Cabinet
A computer cabinet contains major internal hardware components.
- Motherboard
- CPU
- RAM
- Power Supply Unit
- Hard Disk / SSD
- Cooling Fan
- Graphics Card
- Network Card
- Optical Drive
External Ports
- USB Port
- HDMI Port
- VGA Port
- Audio Jack
- Ethernet Port
Important Differences
RAM vs ROM
| RAM | ROM |
|---|---|
| Volatile | Non-volatile |
| Temporary | Permanent |
| Read and Write | Mainly Read Only |
HDD vs SSD
| HDD | SSD |
|---|---|
| Mechanical Device | Electronic Device |
| Slower | Faster |
| Cheaper | Costlier |
Exam Preparation Questions
Short Questions
- Define CPU.
- What is RAM?
- What is Instruction Format?
- Define Bus.
- What is Microprocessor?
Long Questions
- Explain CPU with diagram.
- Describe types of memory.
- Explain instruction cycle in detail.
- Discuss system buses.
- Explain components inside a computer cabinet.
Conclusion
These detailed notes on Unit 2: The Computer System Hardware are highly useful for BSc CSIT 1st Semester IIT students. Read regularly, revise important definitions, and practice exam questions for better results.