Ahh...good old ASM (Assembly).
Assembly is probably the lowest level (next to hardware level) computer language out there. ASM is not used very much any more by professional programmers that have moved on to languages like C++. But ASM and even the language C are great for coding hardware drivers, software that targets specific pieces of hardware, and even operating systems. The Linux kernel is an example of an operating system coding in C with some ASM at the core of the kernel...if that makes sense. Basically, ASM gives you complete control over the hardware. With that said, one can do massive amounts of damage if they are not careful about what they are doing

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Check out Wikipedia for a full explanation of the language:
http://en.wikipedia.org/wiki/Assembly_language