An Introduction to C for Windows

An Introduction to C for Windows, published by SANS Institute on April 3, 2026, is a field guide and reference poster for security professionals learning to develop offensive tools for Windows using C. Created by Jonathan Reiter, author of SANS SEC670: Red Teaming Tools, the poster covers foundational C concepts essential for Windows development, including entry points, data types, strings, pointers, functions, and structures, with emphasis on practical Windows-specific patterns and security considerations.

Key findings:

• Windows uses uppercase data type aliases (DWORD, ULONG, PCHAR, etc.) that map to standard C types; these are defined in minwindef.h and total approximately 1,200 named typedefs
• The entry point for Windows C programs compiled with MSVC must be named main and returns 0 by default; Visual Studio project settings typically leave the Entry Point field empty, defaulting to main
• Strings in C are character arrays terminated with a null byte (\0); this null terminator is critical to functions like strlen(), strcpy(), and gets(), and its absence introduces buffer overflow vulnerabilities
• Mixing signed and unsigned variable types during initialization or operations produces silent bugs; an unsigned ULONG initialized with a negative value rolls over to an astronomically large number
• The strlen() function returns character count (excluding null byte), while sizeof() returns total bytes; using strlen() requires adding 1 to the count when allocating memory or copying with null termination
• Pointers hold memory addresses, not immediate values; the & operator obtains an address, the * operator dereferences it to read or write values at that address
• Pointer arithmetic advances by the size of the type being pointed to; incrementing a PCHAR advances by 1 byte, a PULONG by 4 bytes, and a PWORD by 2 bytes
• Functions require a return type, calling convention (WINAPI standard for Windows), name, and parameters; every function has a signature separating it from others
• Structures represent contiguous memory blocks with named fields at specific offsets; Windows uses structures extensively (processes, threads, PE files, linked lists) and developers must understand field alignment, padding, and initialization
• The ternary operator (condition ? valueIfTrue : valueIfFalse) provides compact conditional assignment; strcmp() comparisons often pair it with format strings for formatted output

The poster emphasizes that string null termination, signed/unsigned type safety, proper use of strlen() vs sizeof(), and understanding pointer mechanics are not academic details but practical requirements that directly impact code security and stability when developing Windows implants and offensive tools. Methodology: This is a course-affiliated reference poster rather than a research survey; it distills core C programming concepts and Windows-specific patterns taught in SANS SEC670.