Your function will only use the lower 8 bits and ignore anything above that. For an alternative, it depends on what you want to do: get a working solution or learn about binary arithmetic and how to deal with bits "by hand". For everything up to 32 or 64 bit depending on your CPU, the following will do:

If you want to do it yourself, consider using a loop starting with a bitmask of 0x80000000 that you right-shift in each step after masking the input value and outputting the corresponding bit.