Difference between SOLVE and solve

[akmon]

Hello again.

I would like to understand definitly the differences between commands in upper or lowercase.

In this case, I search "solve" in the catalog, I type solve(x^2+x+1) in CAS mode and I get {1/2*(SQR(3)*i-1), 1/2*(-SRQ(3)*i-1)}. If I type solve(X^2+X+1) in HOME I get the same result (X in uppercase).

SOLVE in uppercase does not exist in catalog, but, when I manually type it in HOME mode I don´t get Syntax error. It runs and outputs {Error: Extremum found, -0,4921875}.

Even if I type SOLVE in CAS mode, I get ["Error: Extremum found"].

So resuming all the combinations:

solve is a CAS command that works on CAS or HOME mode, I only have to type variables in upper or lowercase.

SOLVE does not exists in catalog, but the calculator recognizes it and it works, with differents results.

So, how is the way that solve or SOLVE works? I have used SOLVE in a little program (IRR, see thread) and it works flawlessly, but I don´t know when is more suitable using solve or SOLVE.

I suppose this example can be applied to other lowercase commands.

Thank you.