Programs that make a computer useful for everyday tasks are known as __________.

Match the following operating systems to their descriptions:

I. DOS II. Mac OS III. Linux IV. UNIX V. Windows A. mainframe operating system B. file names up to 255 characters C. 8.3 convention D. PC operating system with case sensitive file names E. long file names but not always with file extensions

Which of the following causes of signal loss is defined as differences in density between air masses over distance?

A. reflection B. absorption C. scattering D. refraction