There's no OS with integrated data conversion, at most there's integrated compression, which can reduce the overhead:
Code:
Z:\052>compact /c /f /exe:lzx book1 book1.bit
Compressing files in Z:\052\
book1 768771 : 335872 = 2.3 to 1 [OK]
Compressing files in Z:\052\
book1.bit 6150168 : 532480 = 11.6 to 1 [OK]
2 files within 2 directories were compressed.
6,918,939 total bytes of data are stored in 868,352 bytes.
The compression ratio is 8.0 to 1.
Z:\052>compact *
Listing Z:\052\
New files added to this directory will not be compressed.
768771 : 335872 = 2.3 to 1 l book1
6150168 : 532480 = 11.6 to 1 l book1.bit
Normally you'd either just use binary i/o which is available in all popular programming languages, for example:
https://stackoverflow.com/questions/...-i-o-in-python
Or some standalone converter utilities, like "cat input | bit2hex | process | hex2bin > output"