Introduction to Architecture of Computer Systems

1. Basic Components of Computer Architecture

a. Central Processing Unit (CPU)

Also called the brain of the computer.
Executes instructions and controls other components.
Main Parts:
- Control Unit (CU): Directs operations.
- Arithmetic Logic Unit (ALU): Performs arithmetic and logical operations.
- Registers: Small, fast memory to store intermediate data.

Example:
When you press a calculator key, the ALU performs the operation (e.g., 5 + 3).

b. Memory

RAM (Random Access Memory): Temporary, volatile storage used during active processes.
Cache: High-speed memory located in/near the CPU for frequently used data.
ROM (Read-Only Memory): Non-volatile memory containing startup instructions (BIOS).

Example:
Opening MS Word loads it into RAM; frequently accessed functions (e.g., bold text) might be cached.

c. Input/Output Devices

Input Devices: Keyboard, mouse, scanner.
Output Devices: Monitor, printer, speakers.
I/O Controllers manage communication between CPU and devices.

Example:
Typing on a keyboard sends data through an I/O controller to the CPU for processing.

d. Storage Devices

Primary Storage: RAM and Cache.
Secondary Storage: Hard Drives (HDDs), Solid-State Drives (SSDs).
Tertiary Storage: External or cloud storage for backups.

Example:
Saving a document writes data from RAM to HDD or SSD.

2. Instruction Sets and Data Representation

a. Instruction Set Architecture (ISA)

Set of basic commands a CPU can understand.
Includes instructions like load, store, add, jump.

Example (Assembly):

assembly

CopyEdit

MOV A, #5 ; Move value 5 into register A

ADD A, B ; Add content of B to A

b. Data Representation

Binary: Base-2 (e.g., 1010)
Hexadecimal: Base-16 (e.g., A = 10)
ASCII: Character encoding (e.g., ‘A’ = 65)

Example:
Binary 01000001 = ASCII ‘A’, Hexadecimal 41.

3. Memory Hierarchy and Data Flow

a. Memory Hierarchy (Speed vs Size)

Registers (fastest, smallest)
Cache
RAM
SSD/HDD (slowest, largest)

b. Data Flow

Data moves from storage → RAM → CPU for processing.
Results are stored back or displayed via I/O.

Example:
Opening a photo:

HDD → RAM → CPU (for editing) → Monitor (output).

4. System Performance and Troubleshooting

a. System Performance Factors

Clock speed (GHz): Faster CPU cycles.
RAM size: More programs can run simultaneously.
Cache size: Reduces access time.
Bus width: Affects data transfer rates.

Example:
A computer with 8 GB RAM runs multiple applications faster than one with 2 GB.

b. Troubleshooting Techniques

Check POST errors (beeps)
Monitor CPU and RAM usage
Use Device Manager for hardware issues
Replace or reseat components (RAM, cables)

Example:
If a PC is slow, check Task Manager for memory usage or disk bottlenecks.

Conclusion

Understanding computer architecture enables effective programming, system design, and hardware troubleshooting. It bridges software and hardware, helping students design efficient systems and resolve technical issues