local -- mark a variable as local to a subroutine

 
sub foo() 

  local a,b,c$,d(10),e$(5,5) 

  ... 

end sub 

The local-command can (and should be) used to mark a variable (or array) as local to the containing subroutine. This means, that a local variable in your subroutine is totally different from a variable with the same name within your main program. Variables which are known everywhere within your program are called global in contrast.
Declaring variables within the subroutine as local helps to avoid hard to find bugs; therefore local variables should be used whenever possible.

Note, that the parameters of your subroutines are always local.

As you may see from the example, local arrays may be created without using the keyword dim (which is required only for global arrays).

a=1 
b=1 
print a,b 
foo() 
print a,b 

sub foo() 
	local a 
	a=2 
	b=2 
end sub 

This example demonstrates the difference between local and global variables; it produces this output:
1 1 
1 2 
As you may see, the content of the global variable a is unchanged after the subroutine foo; this is because the assignment a=2 within the subroutine affects the local variable a only and not the global one. However, the variable b is never declared local and therefore the subroutine changes the global variable, which is reflected in the output of the second print-statement.