Hexadecimal File Viewer (x86 Assembly, MS-DOS)

This is a 16-bit x86 Assembly project written for the MS-DOS environment. The program reads the contents of one or more files and displays them in hexadecimal format. It includes features such as file offset display, multi-file support, pagination with dynamic screen updates, and enhanced user experience with timestamps and file paths.

---

👤 Author

Aliaksei Zimnitski
Date: 26.02.2025

---

✅ Features

• ✅ Hexadecimal output of file content (byte-by-byte)
• ✅ Offset counter printed at the start of each line
• ✅ Supports multiple input files (via command-line)
• ✅ Optional pagination with -p flag (20 lines per screen)
• ✅ Timestamp and full file path shown during pagination
• ✅ Handles newline characters and line wrapping
• ✅ External procedures for modularity:
  • print_hex – prints a byte in hexadecimal
  • print_date – prints current date/time
  • print_dec – prints offset values in decimal format
• ✅ Fully commented in English

---

🛠 Compilation & Execution Instructions

In MS-DOS or DOSBox:

1) tasm main.asm      ; Assemble main module
2) tasm hex.asm       ; Assemble print_hex procedure
3) tasm dec.asm       ; Assemble print_dec procedure
4) tasm date.asm      ; Assemble print_date procedure
5) tlink main hex dec date
6) main -h                     ; Show help
7) main -p file1.txt file2.txt ; Paginate multiple files

---

🧠 How It Works

• Uses DOS interrupts (int 21h) for file I/O and text output
• Reads file contents in 128-byte chunks
• Tracks the file offset to label each hex-dump line
• Every 70 characters or 20 lines, inserts a page break
• On -p, displays timestamp and file path before continuing

---

📄 Command-Line Usage

main [-h] [-p] <file1> [file2] [...]

• -h → Show help message
• -p → Enable pagination
• <file> → One or more file names to display

Example:

main -p data1.txt data2.txt

---

🧪 Testing Notes

Tested with:

• Empty files ✅
• Files > 64KB (offset wraps due to 16-bit counter) ✅
• Long file paths ✅
• Missing files or permission issues → Error handler triggered ✅

---

🔍 Known Limitations

• Cannot process files over 64KB without offset overflow
• Terminal width fixed to 70 characters
• Only ASCII-compatible input is properly rendered

---

💡 Possible Enhancements

• Use extended memory (XMS/EMS) for larger files
• Implement keyboard navigation (next/prev page)
• Add binary and ASCII views alongside hexadecimal
• Allow filtering or highlighting bytes