What exactly does this question mean ?

[manasij7479]

Write a program to compress a data file using bit field method. Write another program to decompress the above file.

I know what bit fields are.
But what exactly is "bit field method" ?
I think that if the file is a text file, I can use 7 bits for each char and dump structs full of 7 bit chars to a binary file which will be slightly smaller in size.
But that would not work at all for a general 'data' file !

Is there an algorithm that uses bit fields to compress raw data ?

[anduril462]

Perhaps they meant this: Bit array - Wikipedia, the free encyclopedia. Also known as run-length encoding.