Complex sentence: In programming languages with only two levels of visibility, local variables are contrasted with global variables, on the other hand, many ALGOL-derived languages allow any number of levels of nested functions with private variables, functions, constants and types hidden within them.
Split into simpler sentences: In programming languages with only two levels of visibility, local variables are contrasted with global variables. On the other hand, many ALGOL-derived languages allow any number of levels of nested functions with private variables, functions, constants and types hidden within them.