Files with .DCM extension represent a digital image that stores medical information of patients such as MRIs, CT scans, and ultrasound images. DCM files use DICOM (Digital Imaging and Communications in Medicine) image file format and can include patient’s information for reference. It was developed by the National Electrical Manufacturers Association (NEMA) and was meant to standardize the imaging file format for distribution and viewing of medical images.
An XPS file represents page layout files that are based on XML Paper Specifications created by Microsoft. This format was developed by Microsoft as replacement of EMF file format and is similar to PDF file format, but uses XML in layout, appearance, and printing information of a document. It is, in fact, more justified to say that XPS is an attempt on PDF, but couldn't get enough popularity as owned by PDF for a number of reasons.
You can also convert DCM into many other file formats. Please see the complete list below.