I'd wager that like many long-running products out there, they're a mixture of languages, perhaps mainly C/C++, with sprinkling of other languages for specific functionality.
it must be created with a language that gets very close to machine code - for efficiency - and i would expect quite a bit is in inline machine code/assembly language.
I am sure you definitely could not do this in any language without access to a pointer data type. (such as VB/VBA)