from where i can start learn shaders ?

hi
i am working since 1 year ago with unity
but i never work in shader
i am programmer
so i tried to read about shaders today
i got , that it is not simple thing
it is something need study a lot of hard time work
so i am facing now 3 tutorials about shader
what you advice me to start with ?

• Tutorial: ShaderLab & Fixed Function Shaders
• Tutorial: Vertex and Fragment Shaders
• Surface Shaders

 

These are pretty good,
http://cgcookie.com/unity/cgc-courses/introduction-to-surface-shaders-in-unity/
http://unitygems.com/noobshader1/ (and other parts there too)

this one was quite beginner friendly also (but not free)
http://www.digitaltutors.com/tutorial/1438-Introduction-to-Scripting-Shaders-in-Unity

 

http://en.wikibooks.org/wiki/Cg_Programming/Unity