Variable declarations Variables can be declared as either being global or local. Global variables are visible to all functions and on the command line. Local variables are visible only within a single function or command sequence. When the function or command sequence returns, the local variables are deleted. To declare one or more variables, the 'local' or 'global' keywords are used, followed by the desired list of variable names, separated by commas. The definition is terminated with a semicolon. Examples of declarations are: local x, y, z; global fred; local foo, bar; Within function declarations, all variables must be defined. But on the top level command line, assignments automatically define global variables as needed. For example, on the top level command line, the following defines the global variable x if it had not already been defined: x = 7 Variables have no fixed type, thus there is no need or way to specify the types of variables as they are defined. Instead, the types of variables change as they are assigned to or are specified in special statements such as 'mat' and 'obj'. When a variable is first defined using 'local' or 'global', it has the null type. If a procedure defines a local variable name which matches a global variable name, or has a parameter name which matches a global variable name, then the local variable or parameter takes precedence within that procedure, and the global variable is not directly accessible. There are no pointers in the calculator language, thus all arguments to user-defined functions are normally passed by value. This is true even for matrices, strings, and lists. In order to circumvent this, the '&' operator is allowed before a variable when it is an argument to a function. When this is done, the address of the variable is passed to the function instead of its value. This is true no matter what the type of the variable is. This allows for fast calls of functions when the passed variable is huge (such as a large array). However, the passed variable can then be changed by the function if the parameter is assigned into. The function being called does not need to know if the variable is being passed by value or by address. Built-in functions and object functions always accept their arguments as addresses, thus there is no need to use '&' when calling built-in functions.