How much of a language do professional programmers/ software devs use?

[Atreyo Bhattacharjee]

How much do programmers remember and use of their primary language? Basically what I'm trying to ask is, is it expected for a professional to know everything about a language or development tool? Or do pros also use references and the internet to look stuff up?

 

[mwryder55]

I wrote my first program to run on an IBM mainframe 45 years ago and have been programming for a living for the last 38 years.
I know most of the features of my primary language and know what other features are available. I only use the references to look up specific settings of a feature that I do not normally use.
When I am learning a new language and/or library like my current studies of C# and .NET I use the internet a lot more. I still have an idea of what they can do but not necessarily the exact way to do something. Using Visual Studio for this helps a lot with reminding me of what I need to do.