The usage is as follows

./resize 4 small.bmp student.bmp ~cs50/pset4/resize 4 small.bmp staff.bmp ~cs50/pset4/peek student.bmp staff.bmp

Which should let you compare headers of student.bmp and staff.bmp

The usage is as follows

./resize 4 small.bmp student.bmp
~cs50/pset4/resize 4 small.bmp staff.bmp
~cs50/pset4/peek student.bmp staff.bmp

Which should let you compare headers of student.bmp and staff.bmp