Memory Management Simulator

Author: Ayush Jha

This project simulates contiguous memory allocation using three classic algorithms:

• First-Fit: Allocates the first hole large enough
• Best-Fit: Allocates the smallest hole that fits
• Worst-Fit: Allocates the largest available hole

The program runs all three strategies on the same input and reports the results for comparison.

• O(log n) efficient hole management using TreeMap data structure
• Automatic hole merging when memory is deallocated
• External fragmentation tracking when allocation fails
• Runs all three allocation strategies in a single execution

MemoryManagement/
├── src/
│   ├── Driver.java              # Main program with simulation logic
│   ├── MemoryAllocations.java   # Represents memory operation requests
│   ├── TakenBlocks.java         # Represents allocated memory blocks
│   └── input.txt                # Sample input file
├── bin/                         # Compiled classes directory
└── build.bat                    # Windows build script

Main program that:

• Loads memory operations from input file
• Runs simulations for all three strategies
• Implements allocation algorithms and hole management
• Contains Strategy enum (FIRST_FIT, BEST_FIT, WORST_FIT)

Immutable command object representing a memory operation:

• refNum: Process ID
• operation: 1 = Allocate, 2 = Deallocate
• argument: Size (if allocating) or Process ID to free (if deallocating)

Represents an allocated memory block:

• refNum: Process ID that owns the block
• startPoint: Starting memory address
• endPoint: Ending memory address

Each line contains three integers: x1 x2 x3

• x1: Process reference number (ID)
• x2: Operation type
  • 1 = Allocate memory
  • 2 = Deallocate memory
• x3:
  • If x2=1: Number of bytes to allocate
  • If x2=2: Process ID to deallocate

Example:

1 1 37    # Process 1: Allocate 37 bytes
2 1 17    # Process 2: Allocate 17 bytes
3 2 1     # Process 3: Deallocate Process 1's memory

Note: Maximum memory is set to 1024 bytes in Driver.MAX_MEMORY

Option 1: Using the batch file

cd MemoryManagement
build.bat

Option 2: Manual compilation

cd MemoryManagement\src
javac Driver.java MemoryAllocations.java TakenBlocks.java
java Driver

cd MemoryManagement/src
javac Driver.java MemoryAllocations.java TakenBlocks.java
java Driver

cd MemoryManagement/src
make
java Driver

The program outputs results for all three strategies:

On Success:

First-Fit Results:
Success.

On Failure:

Best-Fit Results:
Process 42 failed to allocate 64 bytes. External Frag: 158

This indicates:

• Process 42 could not be allocated
• Requested 64 bytes
• Total free memory (external fragmentation) was 158 bytes (but too fragmented)

• Allocation: O(n) where n = number of holes
• Deallocation with merging: O(log n) using TreeMap's floor/ceiling operations
• Space: O(n) for storing holes and allocated blocks

With the included input.txt:

• First-Fit: ✓ All allocations succeed
• Best-Fit: ✗ Process 42 fails (158 bytes fragmented)
• Worst-Fit: ✗ Process 31 fails (196 bytes fragmented)

This demonstrates how different strategies affect fragmentation and allocation success.