docs(amiga): complete AmigaOS 3.1/3.2 developer reference — 172 files across 17 sections

Comprehensive technical documentation covering:
- Hardware: OCS/ECS/AGA custom chip registers, Copper & Blitter deep dives
- Boot sequence: cold boot through startup-sequence
- Binary format: HUNK executable spec, relocation, debug info
- Linking & ABI: .fd files, LVO tables, register calling conventions
- Exec kernel: tasks, interrupts, memory, signals, semaphores
- AmigaDOS: file I/O, FFS/OFS layout, CLI/Shell scripting
- Graphics: planar bitmaps, Copper programming, HAM/EHB modes
- Intuition: screens, windows, IDCMP, BOOPSI
- Devices: trackdisk, SCSI, serial, timer, audio, keyboard
- Libraries: utility, expansion, IFFParse, locale, ARexx
- Networking: bsdsocket API, SANA-II, TCP/IP stack comparison
- Toolchain: GCC, vasm/vlink, SAS/C, NDK, debugging
- Reverse engineering: IDA/Ghidra setup, compiler fingerprints, case studies
- CPU & MMU: 68040/060 emulation libs, PMMU, cache management
- Driver development: SANA-II, Picasso96/RTG, AHI audio

All files include breadcrumb navigation. No local paths or proprietary content.

07_dos/dos_base.md

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+[← Home](../README.md) · [AmigaDOS](README.md)
+
+# DosLibrary — Structure and Global State
+
+## Overview
+
+`dos.library` is opened by nearly every Amiga program. The library base `DOSBase` is a `struct DosLibrary` that extends `struct Library` with process-level state, the root node, and handler management.
+
+---
+
+## struct DosLibrary
+
+```c
+/* dos/dosextens.h — NDK39 */
+struct DosLibrary {
+    struct Library  dl_lib;           /* standard Library header */
+    struct RootNode *dl_Root;         /* pointer to the system root node */
+    APTR            dl_GV;            /* BCPL global vector */
+    LONG            dl_A2;            /* BCPL scratch */
+    LONG            dl_A5;            /* BCPL scratch */
+    LONG            dl_A6;            /* BCPL scratch */
+    struct ErrorString *dl_Errors;    /* error string table */
+    struct timerequest *dl_TimeReq;   /* timer.device request */
+    struct Library  *dl_UtilityBase;  /* cached UtilityBase */
+    struct Library  *dl_IntuitionBase;/* cached IntuitionBase */
+};
+```
+
+---
+
+## struct RootNode
+
+```c
+struct RootNode {
+    BPTR   rn_TaskArray;   /* BPTR to CLI task array */
+    BPTR   rn_ConsoleSegment; /* console handler segment */
+    struct DateStamp rn_Time; /* current system time */
+    LONG   rn_RestartSeg;  /* restart segment */
+    BPTR   rn_Info;        /* BPTR to DosInfo */
+    BPTR   rn_FileHandlerSegment;
+    struct MinList rn_CliList; /* list of CLI processes */
+    /* ... OS 3.x additions ... */
+    ULONG  rn_BootFlags;
+    APTR   rn_BootProc;
+};
+```
+
+---
+
+## Opening dos.library
+
+```c
+struct DosLibrary *DOSBase;
+DOSBase = (struct DosLibrary *)OpenLibrary("dos.library", 40);
+if (!DOSBase) { /* OS 3.1 or later required */ }
+```
+
+---
+
+## BCPL Heritage
+
+AmigaDOS was originally written in BCPL. Artifacts remain:
+- **BPTR** — pointers right-shifted by 2 (`real = bptr << 2`)
+- `dl_GV` — BCPL global vector (used internally by filesystem handlers)
+- File handles and locks are BPTRs, not real pointers
+
+```c
+/* Convert BPTR to C pointer: */
+#define BADDR(bptr) ((APTR)((ULONG)(bptr) << 2))
+```
+
+---
+
+## References
+
+- NDK39: `dos/dosextens.h`, `dos/dos.h`
+- ADCD 2.1: dos.library autodocs