What You'll Find Here
The TECH Topics area organizes the core reference material of Tech Help! into focused categories. Whether you need the assembly instruction set, ROM BIOS details, DOS function indexes, or data-structure layouts, each topic provides concise technical documentation aimed at assembly-language programmers working in DOS environments.
- Assembly Instruction Set — opcodes, effective address calculations, clock cycles for the 8088, flags register, and the System ID Byte.
- ROM BIOS Details — low-memory usage maps, addressing modes, and system-level conventions.
- MASM Reference — pseudo-ops, operator precedence tables, and reserved words for the Microsoft Macro Assembler.
- DOS & BIOS Data Structures — the Program Segment Prefix (PSP), FCB fields, swappable data areas, and interrupt vectors.
- DOS & BIOS Service Index — function numbers, interrupt calls, error codes, and file attributes.
Assembly Language
Complete reference for the assembly instruction set, effective address computation, 8088 clock cycles, flags register, low-memory usage, and the System ID Byte. Includes MASM pseudo-ops, operator precedence, and reserved words.
Explore Assembly →DOS & BIOS Services
Indexed listing of DOS functions and BIOS extensions with interrupt numbers, function codes, error codes, and file attributes. Covers standard handles and extended DOS capabilities.
Browse Services →Data Structures
Detailed documentation of the Disk Transfer Address (DTA), Program Segment Prefix (PSP), FCB fields, and interrupt vectors including INT 22H (Terminate) and INT 23H (Ctrl-Break).
View Structures →How to Use TECH Help!
Guidance on navigating the reference book, using the search functionality, and moving between Home, Back, and specific topic pages. Covers exit procedures from Help! sessions.
Read the Guide →