How to Use TECH Help!

TECH Help! is an electronic reference book designed for quick lookup of DOS programming information. It covers assembly instructions, BIOS services, DOS functions, and low-memory data structures. Navigating it efficiently will save you time during development.

Navigation

The reference is organized into major topic areas. Use the Home link to return to the main index at any point. The Back function returns you to the previous page you were viewing. Specific topic pages — such as the Assembly Instruction Set, DOS & BIOS Data Structures, and Reference Tables — are reachable from the main index and from cross-links within related pages.

Search

A search facility is available to locate specific functions, interrupts, or topics by keyword. Enter a term such as an interrupt number (e.g., INT 23H), a DOS function (e.g., fn 1aH), or a structure name (e.g., PSP) to jump directly to the relevant entry.

Exiting Help!

To leave the TECH Help! reference, use the Exit from Help! command. This terminates the reference session and returns control to the calling environment. Any unsaved navigation state is discarded on exit.

Tip: When browsing deeply nested topics, use the Home and Back links to stay oriented. The Sitemap provides a complete overview of every page and section available in the reference.

Topic Areas

Assembly — Instruction set details, effective address calculations, clock cycles for the 8088, flags register, MASM pseudo-ops, operator precedence, and reserved words.
DOS & BIOS — DOS functions and interrupts, error codes, file attributes, standard handles, PSP description, FCB fields, and swappable data areas.
Tables — ASCII chart, line-drawing characters, special characters, color codes, and keyboard scan codes.