Update README.md

README.md

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-# ShellcodeStdio
+### ShellcodeStdio
 A mini-framework for easily writing debuggable, compiler optimized, position independent, x86 shellcode for windows platforms.
 
-For usage see main.cpp
+For basic usage see main.cpp
 
-# Suggested Compiler Options
+### Suggested compiler options
 ```
 C/C++ -> Optimization -> /O1, /Ob2, /Oi, /Os, /Oy-, /GL
 C/C++ -> Code Generation -> /MT, /GS-, /Gy
 Linker -> General -> /INCREMENTAL:NO
+```
+### How do I use this?
+When working with this framework, and coding shellcode in general, you'll have to keep a few things in mind:
+
+1. You must declare all your variables on the stack.
+2. Strings are no exception. This is how to create a char*, wchar_t* on the stack. Don't forget to null-terminate.
+```C++
+unsigned char str[] = { 'E', 'x', 'a', 'p', 'l', 'e', 0 }; 
+unsigned char w_str[] = { 'E', 0, 'x', 0, 'a', 0, 'm', 0, 'p', 0, 'l', 0, 'e', 0, 0 };
+```
+3. If you want to use an external function (i.e Windows API) you must first ensure the module containing the function is loaded into the current process. 
+4. The second part of calling an external function is calling the DEFINE_FUNC_PTR or DEFINE_FWD_FUNC_PTR macro with the name of the module and the typedef of the function you want to call.
+
+### Hello World Example
+```C++
+CHAR strUser32[] = { 'u','s','e','r','3','2','.','d','l','l',0 };
+CHAR strMboxTitle[] = { 'S','h','e','l','l','S','t','d','i','o', 0 };
+CHAR strMboxMsg[] = { 'H','e','l','l','o',' ', 'W','o','r','l','d','!',0 };
+
+DEFINE_FUNC_PTR("kernel32.dll", LoadLibraryA);
+LoadLibraryA(strUser32);
+
+DEFINE_FUNC_PTR("user32.dll", MessageBoxA);
+MessageBoxA(NULL, strMboxMsg, strMboxTitle, MB_OK);
+```
+
+### Misc
+* If you wish to add a function you must keep it between the MalCodeBegin and MalCodeEnd markers. 
+* Don't forget to call the ScStdio::MalCode() at some point, otherwise when compiling in release with the suggested switches, the code will optimized away.