If you're using an int variable for keeping a decimal value and you want to convert it into a binary value, you should know how an int is represented.
An "int" uses 32 bits for representing the number. You can use binary operators in C++ to get the bytes. (OR / AND). I suggest that you do a search on what they are and how to use them. If you don't know the binary representation, do the same.
It's very easy to print all the bytes of an int. You can use a printf option of write a loop that will iterate 32 times to print every byte of the int.