The code window allows you to see the HLSL, GLSL, or assembly code of the current draw call, along with the constants or uniforms passed into the shader. Keyword highlighting is available to aid in reading the shader code and the initial entrypoint is also highlighted with a blue background to make it easy to identify.
In DirectX10 the shaders must be compiled with the D3D10_SHADER_DEBUG flag in order for the HLSL code to be available.
In DirectX11 the shaders must be compiled with the D3DCOMPILE_DEBUG flag in order for the HLSL code to be available.
DirectX11 compute shaders, pixels shaders, and vertex shaders can be debugged using the
Shader Debugger functionality of this window. The blue hammer icon along the top of the window is visible and enabled if the shader is debuggable. DirectX11 shaders can be edited using the
Shader Editing functionality of this window. The icon showing a pen and paper will be active (blue) if the shader is editable.