up [ integer-constant ]The up command replaces the current local environment by the environment of one of its caller. It takes a single numeric argument which determines how far up the chain of calls it should go. For example, assuming we begin in the environment of the current active procedure, "up 1" makes the caller of the active function the current local environment while `up 3" makes the caller of the caller of the caller of the active function the current local environment. Note that an "up 1" immediately followed by an "up 2" is equivalent to an "up 3'. If the argument is omitted a value of 1 is assumed. If the argument value exceeds the number of functions on the call chain above the current local environment, the environment of the initial invocation of the function main becomes the current local environment.
down [ integer-constant ]
The down command replaces the current local environment by the environment of one of the functions below it on the current call chain. Like the up command, it takes a single numeric argument which determines how many steps along the call chain it should take. If this argument is omitted, 1 is assumed. If the argument exceeds the number of calls made below the current local environment, the function that was executing when a breakpoint occurred again becomes the current local environment.