The Lotus C API allows programmers to build C programs that can access Lotus Notes/Domino functionality. The Lotuc C API is a set of subroutines and data structures that are written in C. These sub routines can be called from C programs. These functions make available significant functions of the Lotus Notes/Domino platform without having to go through the user interface. The best point to start on the Lotus C API is the C API 6.5 User's Guide for Domino and Notes. This is a download that has a compressed NSF file. For your quick reference here is the table of contents of this guide:

Preface 
1 Audience for this Guide 
2 Documentation Overview 
3 Known Problems, Corrections, and Additions 
1 Introduction 
1 Overview of the Lotus C API for Notes/Domino 
2 New Features in Lotus C API Toolkit for Notes/Domino 6 
3 Changes to Lotus C API Toolkit for Notes/Domino 6 
4 New Features in Lotus C API Toolkit for Notes/Domino 6.0.1 
5 Changes to Lotus C API Toolkit for Notes/Domino 6.0.1 
6 New Features in Lotus C API Toolkit for Notes/Domino 6.0.2 
7 Changes to Lotus C API Toolkit for Notes/Domino 6.0.2 
8 New Features in Lotus C API Toolkit for Notes/Domino 6.0.3 
9 Changes to Lotus C API Toolkit for Notes/Domino 6.0.3 
10 New Features in Lotus C API Toolkit for Notes/Domino 6.5 
11 Changes to Lotus C API Toolkit for Notes/Domino 6.5 
12 Software Compatibility 
13 Migration Issues 
2 The Lotus C API Toolkit for Notes/Domino 6.5 
1 Contents of the Lotus C API Toolkit for Notes/Domino 6.5 
2 Reference 
3 Sample Programs 
3 Platform Specifics 
1 Building 32-bit Windows Applications 
2 Building UNIX Applications 
3 Building iSeries Applications 
4 Building Macintosh Applications 
4 Program Structure 
1 Overview 
2 NotesMain versus Main 
3 Windows Applications 
4 Server Add-In Tasks 
5 Basic Operations 
1 The Parts of a Domino Database 
2 Copying Domino Databases and Documents 
3 Reading Documents 
4 Writing Documents 
6 Views 
1 Structure 
2 Tips on Using Views 
3 Listing the Documents in a View 
4 Searching a View Index 
5 Advanced Operations 
6 Folders 
7 Rich Text Fields 
1 Introduction to Rich Text 
2 Tables 
3 Document Links 
4 DDE Links 
5 Edit-Level File Imports 
6 Finding the Components of a Rich Text Field 
7 Font Tables 
8 Embedding and Extracting OLE 2 Objects 
9 Hotspots 
8 Database Design 
1 Forms and Frames 
2 Views 
3 Navigators 
4 Release 3 Agents 
5 Agents 
6 Evaluating Formulas 
9 System Administration 
1 Security 
2 Access Control Lists 
3 Setting Document Read Access 
4 Document-Level Security Fields 
5 Field-Level Security 
6 Server and Database Listings 
7 Selective Replication 
8 Events 
9 Backup and Recovery 
10 Domino Upgrade Services (DUS) 
11 Domino Web Server Application Interface (DSAPI) 
12 Lightweight Directory Access Protocol (LDAP) 
13 Activity Logging 
14 Single Sign-On with Domino and WebSphere 
10 Electronic Mail 
1 Overview of Messaging Interfaces 
2 Domino Mail Architecture 
3 Sending and Receiving Mail 
4 Domino Mail Gateways 
5 Vendor Independent Messaging (VIM) 
6 Unified Messaging Solutions 
11 Miscellaneous Topics 
1 Import and Export Libraries 
2 Encryption/Decryption 
3 Response Documents 
4 Menu Add-In Programs 
5 User-Defined Data Types 
6 Network Send and Receive 
7 External Database Drivers 
8 Notes/FX and NotesFlow 
9 Signal Handlers 
10 Message Queues 
11 Extension Manager 
12 Multi-Threaded Application Support 
13 Automated Abstracts 
14 Remote LAN Access Product Adapter 
15 Calendar and Scheduling 
12 Platform Issues 
1 Domino Canonical Format 
2 Platform-Specific Naming Conventions 
3 Domino ASP Environment 
13 Advanced Services API 
1 Advanced Services API Features 
2 Server Clusters 
3 Domino Billing 
14 Appendix 
1 Anatomy of a Note ID 
2 Data Types