The business and professional services sector is comprised of primary services including legal, architectural, engineering and consulting and real estate firms, as well as secondary services such as back-office support operations, accounting and payroll services, and processing facilities. Together, these services provide not only highly technical and specialized support services for virtually every sector of the U.S. economy, but also services to handle the routine, day-to-day activities of other companies. Business and professional services firms exist both as subsidiary operations for parent firms as well as outsourced third-party service providers. Back office operations, which interact primarily via electronic communication, often integrate a variety of functions such as customer relations, centralized accounting, and administrative services under one roof, while legal services, real estate, and technical consulting services are often located in independent branch offices.