I'm confused about what you're starting with and where you're trying to go with it. You mentioned HyperTerminal which makes me think you might be starting with a string?
If this is the case, then you might either have a string representation of a integer, or some binary data packed into the string.
If you have a string representation of a decimal number, you'll need to use a command like "Convert String to Integer 32" (or similar). If you have a string representation of a hex number, you could use "Convert Hex String to Number."
If it's "binary" data stored in a string, that's a little more complicated and you have to worry about things like byte order (endianness).
Once you have an Int 32 (or 64), you can use commands like "Bit Test" you mentioned, or the method Nick describes above in PAC Display, to pull one bit from those 32 or 64 bits that make up your Integer 32 or 64.
To help clarify, could you tell us exactly the variable type you're starting with and where it's coming from?
Also, you mention "save the variable as binary form" -- if you wanted to display it (like PAC Control's debugger PSG & I mentioned) you could save it for human viewing in a string (kind of the opposite of what I describe above).
Ultimately, your controller just has a certain number of bytes or bits designated per variable. All data is "binary" (boils down to on/off or 1/0 at the bit level in memory). Normally we don't display it as 1s and 0s because it would just take up too much space, so for humans, we display it as decimal (what most people are used to) or sometimes hex. But there's not need to "convert" or "save as binary" unless it's for the purposes of a human looking at it.
I hope that helps!