Some Predefined Symbols

There are four kinds of symbols that have some form of predefined
meaning within Maple:

* Syntactic parts of the Maple command and programming language. The
meanings of these cannot be redefined.  ("if" and "quit" are typical
examples.)

* System-supplied functions. These may be redefined, but you will lose
the functionality of the system-supplied function. ("solve" and "trace"
are typical examples.)

* Predefined constants and names. Library functions assume that these
symbols exist with no assigned value, so errors or incorrect results
will usually result if they are redefined. ("I", the complex square root
of 1, and "true" are typical examples.)

* System programming variables. These are used to control computational
effects, so they can (cautiously!) be assigned new values. ("Digits" and
"printlevel" are typical examples.)

The global variable "printlevel" is a particularly handy one to know. 
By setting "printlevel := 0;" you turn off the automatic printing of
your commands; setting "printlevel := 1;" is the default behaviour.  See
help('printlevel') for the effect of other settings.