Concept of variables

There are two kinds of variables:

• Global variables: these are always accessible from any location in the program.
• Local variables: these are only accessible in the procedure where they are defined.

In this version of LOGO, local variables are not accessible in sub-procedures. At the end of the procedure, the local variables are deleted.

Primitives	Arguments	Use
make	a b: a word, b anything	If the local variable a exists, assigns it the value b. If not, creates a global variable a and assigns it the value b.
		Eg: make ``a 100 assigns the value 100 to the variable a
local	a: word	Creates a variable called a. Note, this is not initialised. To assign it a value, see make.
localmake	a b: a word, b anything	Creates a new local variable and assigns it the value b.
def, define	word1 list2 list3	Define a new procedure called word1, which requires the variables in list2. The procedure's instructions are contained in list3. def "polygon [nb length] [repeat :nb[fd :length rt 360/:nb]] --> this command defines a procedure called polygon with two variables (:nb and :length). This procedure draws a regular polygon, we can choose the number of sides and their length.
thing	a: word	returns the value of the variable :a. thing "a is similar to :a
erp, eraseprocedure	a: word or list	Deletes the procedure calling ''a`` or all procedures that contains the list ''a``.
erasevariable, erv	a: word or list	Deletes the variable ''a`` or all variables that contains the list ''a``
erasepropertylist, erpl	a: word or list	Deletes the property list ''a`` or all propert lists that contains the list ''a``
erall, eraseall	none	Deletes all the variables, property lists and procedures currently running.
bye	a: none	Quit XLogo.
procs, procedures	none	Returns a list which contains all the procedures currently defined.
variables, vars	none	Returns a list which contains all the defined variables.
pls, propertylists	none	Returns a list which contains all the property lists currently defined.
primitives	none	Enumerates all primitives for the current language.
contents	none	Returns a list which contains 3 lists. The first list contains all procedures names, the second all variables names and the last all propert lists names.
run	a :list	Executes the list of instructions contained in list a.