Clear various quantities from the workspace.
CLEAR removes all variables from the workspace.
CLEAR VARIABLES does the same thing.
CLEAR X removes variable or function X from the workspace.
CLEAR FUNCTIONS removes all compiled M-functions.
CLEAR MEX removes all links to MEX-files.
CLEAR ALL removes all variables, functions and MEX links.
If X is global, CLEAR X removes X from the current workspace,
but leaves it accessible to any functions declaring it global.
CLEAR GLOBAL X completely removes the global variable X.
CLEAR GLOBAL removes all global variables.