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## Global Names

`(defined? symbol)` returns `#t` if a global variable is defined with the name symbol in the current namespace, `#f` otherwise.

`(undefine symbol)` causes symbol to be undefined in the current namespace if it was defined previously.

`(global-defined-value symbol)` returns the value of the global variable named by the symbol in the current namespace. If symbol is undefined, the `exn:variable` exception is raised.

`(global-defined-value symbol v)` sets the value of symbol in the current namespace, defining symbol if it is not already defined.

`(make-global-value-list)` returns an association list that pairs each globally-defined symbol with its current value from the current namespace.

`(built-in-name symbol)` determines whether symbol is the name of a built-in variable. If the symbol can be used within a unit as a built-in variable, then `built-in-name` returns a keyword-form variable symbol that accesses the built-in binding. Otherwise, `#f` is returned. See also section 4.10.2.