SOLUTIONS TO CHAPTER 1 PROBLEMS 1. An operating system must provide the users with an extended machine, and it must manage the I/O devices and other system resources. To some extent, these are different functions. 2. Multiprogramming is the rapid switching of the CPU between multiple processes in memory. It is commonly used to keep the CPU busy while one or more processes are doing I/O. 3. Obviously, there are a lot of possible answers. Here are some. Mainframe operating system: Claims processing in an insurance company. Server operating system: Speech-to-text conversion service for Siri. Multiprocessor operating system: Video editing and rendering. Personal computer operating system: Word processing application. Handheld computer operating system: Context-aware recommendation system. Embedded operating system: Programming a DVD recorder for recording TV. Sensor-node operating system: Monitoring temperature in a wilderness area. Real-time operating system: Air traffic control system. Smart-card operating system: Electronic payment. 4. Empirical evidence shows that memory access exhibits the principle of locality of reference, where if one location is read then the probability of accessing nearby locations next is very high, particularly the following memory locations. So, by caching an entire cache line, the probability of a cache hit next is increased. Also, modern hardware can do a block transfer of 32 or 64 bytes into a cache line much faster than reading the same data as individual words. 5. Input spooling is the technique of reading in jobs, for example, from cards, onto the disk, so that when the currently executing processes are finished, there will be work waiting for the CPU. Output spooling consists of first copying printable files to disk before printing them, rather than printing directly as the output is generated. Input spooling on a personal computer is not very likely, but output spooling is. 6. The prime reason for multiprogramming is to give the CPU something to do while waiting for I/O to complete. If there is no DMA, the CPU is fully occupied doing I/O, so there is nothing to be gained (at least in terms of CPU utilization) by multiprogramming. No matter how much I/O a program does, the CPU will be 100% busy. This of course assumes the major delay is the wait while data are copied. A CPU could do other work if the I/O were slow for other reasons (arriving on a serial line, for instance). 7. Second-generation computers did not have the necessary hardware to protect the operating system from malicious user programs.