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FLED

Simple DOS editor with Hex and Compare functionality

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README

FLED

image

Simple DOS editor with Hex and Compare functionality

FLED (FlabEditor) – Text & Hex Editor

A fast, direct-VRAM text editor with hex and diff modes for DOS

📌 Overview

FLED (FlabEditor) is a lightweight, high-performance text editor written in Pascal for DOS environments. It leverages direct VRAM access and BIOS interrupts for fast rendering and input handling, avoiding slow DOS API calls.

🔹 Key Features

✅ Text Editing – Full cursor navigation, backspace, enter, and typing
✅ File Operations – New, Open, Save (F1–F3)
✅ Search – Find text with highlighted matches and "next match" navigation (F4)
✅ Hex Editor – Direct binary editing with ASCII preview (F6)
✅ File Comparison – Side-by-side diff viewer with Hex/ASCII modes (F5)
✅ Color UI – Customizable colors (CGA/EGA/VGA)
✅ Direct Hardware Access – Fast VRAM writes and BIOS keyboard input

🎯 How to Use

📝 Basic Controls

Key Action
Arrow Keys Move cursor
Page Up / Page Down Scroll viewport
Backspace Delete character
Enter New line
ESC Exit editor

📁 Menu Shortcuts

Key Function Description
F1 New Clear buffer and start fresh
F2 Open Load a file (supports directory navigation)
F3 Save Save current buffer to file
F4 Search Find text, press N for next match
F5 Compare Side-by-side file diff (Hex/ASCII modes)
F6 Hex Mode Switch to hex editor (edit binary directly)
F7 (in Diff) Toggle Mode Switch between Combined, Hex Only, and ASCII Only views

🔍 Search Mode

  1. Press F4 to open search.
  2. Type your query and press Enter.
  3. Matches are highlighted in cyan.
  4. Press N to jump to the next match.
  5. Press ESC to exit.

🔧 Hex Editor Mode

  • Navigation: Arrow keys move the cursor (nibble-level precision).
  • Editing: Type 0–9, A–F to modify bytes.
  • Scrolling: Page Up / Page Down to navigate large files.
  • ASCII Preview: Right side shows printable characters (. for non-printable).
  • Exit: Press ESC to return to text mode (changes sync back to buffer).

📊 File Comparison (Diff)

  1. Press F5 and select two files.
  2. If files match exactly, a confirmation message appears.
  3. View Modes (toggle with F7):
    • Combined: Hex + ASCII diff with color-coded differences (red = mismatch).
    • Hex Only: Side-by-side hex dump.
    • ASCII Only: Side-by-side text comparison.
  4. Navigation: Arrow keys / Page Up / Page Down to scroll.
  5. Exit: Press ESC.

⚙️ Other Information

🖥️ Technical Details

  • Target Hardware: CGA/EGA/VGA (Color text mode, 80x25)
  • VRAM Address: $B800:0000 (direct memory-mapped I/O)
  • Buffer Size:
    • Text: 100 lines × 80 columns
    • Viewport: 23 lines (info bar on row 25)
  • File Handling:
    • Supports binary and text files.
    • Temporary file (FLED$$$.TMP) used for hex ↔ text sync.
  • Keyboard: Uses BIOS Interrupt 16h for fast, buffered input.
  • Cursor Control: BIOS Interrupt 10h for hardware cursor positioning.

🎨 Color Scheme

Color Constant Usage
White on Blue $1F Default text editing area
Black on Light Gray - Menu bar, status bar, dialogs
Light Cyan 11 Search highlights
Light Red 12 Diff mismatches
Light Green 10 File 2 (in diff mode)
Yellow 14 Hex editor headers

📦 Dependencies

  • Compiler: Turbo Pascal or Free Pascal (DOS target)
  • OS: MS-DOS or compatible (requires BIOS interrupts)
  • Hardware: CGA/EGA/VGA display adapter

🚀 Usage Notes

  • Command Line: Launch with a filename to open it immediately:
    bash
    FLED MYFILE.TXT
  • Directory Navigation: In Open dialog, use arrow keys to select files, Enter to open, ESC to cancel.
  • Hex Mode Sync: Changes in hex mode are automatically synced back to the text buffer.
  • Limitations:
    • Max 100 lines (hardcoded MAX_LINES).
    • Lines longer than 80 characters are truncated.
    • No undo/redo functionality.

🐛 Known Quirks

  • Direct VRAM Writes: Bypasses DOS, so some IDEs may crash (hence $R-,S-,I- compiler directives).
  • Extended Keyboard: Uses Int 16h for scan codes (supports Page Up/Down, arrow keys).
  • Temporary File: FLED$$$.TMP is created during hex editing and deleted on exit.

📜 License & Credits

  • Author: (Original code provided)
  • Inspiration: Classic DOS text editors (e.g., Turbo Pascal IDE, Norton Editor)
  • Purpose: Educational / Retro computing

"Fast, minimal, and built for speed—just like the good old days." 🚀