Applications put computers to praticalbusiness (1), but below the (2) it’s the heart of an operating system—the kernel that provides the technical wizardry to juggle multiple program, connect to networks and store(3).A traditional kernal provides all the functions for applications. The kemal (4) memory, I/O devices and parcels out processor time.

The kernel also supports security and fault (5) , which is the ablity to recover automatically when parts of the system fail.

3（）

A．browser

B．repeater

C．router

D．server

（）报告是美国商务部出版局整理出版的研究报告，其内容多侧重于民用技术、生物医学及社会科学方面。