7. How many of the below are FALSE about constants?
I. They may occur on the left of := ( := 赋值 )
II. They may occur on the left of = ( = 比较 )
III. They may occur on the right of :=
IV. They may occur on the right of =
V. They never change in value (inside the program during execution)
VI. They may be printed (i.e. Used in a writeln)
VII. They make code more easily modifiable if we needed to change something during code maintenance
IX. They are converted to their actual value (in the program code) at compile time
(A) 1
(B) 2
(C) 3
(D) 4
(E) More than 4
8. Which types of file organizations are supported by magnetic taps?
(A) Contiguous sequential files
(B) Contiguous sequential files and sequential files with extents
(C) (a) and (b) and indexed sequential files
(D) Random files
(E) All of the above
9. Which sentence can be generated by: S --> aS | bA, A -->d | ccA
(A) bccddd
(B) abbbd
(C) ababccd
(D) aabccd
(E) aadb
10. In terms of expressive poser (of associations) or generality of representation.
(A) Hierarchical is best, relational worst, and network moderate.
(B) Hierarchical is best, relational moderate, and network worst.
(C) Hierarchical is worst, relational moderate, and network best.
(D) Hierarchical is worst, relational best, and network moderate.
(E) Hierarchical is best, relational worst, and network moderate.
11. Access to moving head disks requires three periods of delay before information is brought into memory. The response that correctly lists the three time delays for the physical access of data in the order of their relative speeds from slowest to fastest is
(A) latency time, cache overhead time, seek time
(B) cache overhead time, latency time, seek time
(C) transmission time, latency time, seek time
(D) seek time, latency time, transmission time
(E) queue wait time, cache overhead time, transmission time
12. Object modules generated by assemblers that contain unresolved external references are resolved for two or more object modules by a/an
(A) linker
(B) loader
(C) operating system
(D) debugger
(E) compiler
13. The clock interrupt handler on the SOS computer requires 2 msec per clock tick. The clock runs at 60 HZ. What percent of the CPU is devoted to the clock
(A) 1.2
(B) 7.5
(C) 12
(D) 18.5
(E) 24
14. Four 256 x 8 PROM chips are used to produce a total capacity of 1024x8. How many address bus lines are required?
(A) 4
(B) 8
(C) 10
(D) 16
(E) 32
15. Which application is best handled in ROM
(A) storage for temporary variables
(B) storage for protected passwords
(C) storage for microprograms
(D) storage for information on cabling of terminals, such as which ports have terminals on them
(E) storage of the operating system’s boot sector
16. In a multiprogramming system, a set of processes is deadlocked if each process in the set is waiting for an event to occur that can be initiated only by another process in the set. Which of the following is NOT one of the four conditions that are necessary for deadlock to occur?
(A) mutual exclusion
(B) partial assignment of resources
(C) nonpreemption
(D) process suspension
(E) circular wait
17. Which of the following is false?
(A) Segmentation suffers from external fragmentation
(B) Paging suffers from internal fragmentation
(C) Virtual memory is used only in multi-user systems.
(D) Segmented memory can be paged
(E) Trashing may occur due to too many users on a system
18. Using Pop (S1, Item), Push (S1, Item), Read( Item ), Print (Item), the variables S1 (stack) and Item, and given the input file: A, B, C, D, E, F Which stacks are possible:
(A) 5 | A |
4 | B |
3 | C |
2 | D |
1 | E |
-----
(B) 5 | |
4 | |
3 | D |
2 | A |
1 | F |
-----
(C) 5 | |
4 | |
3 | B |
2 | D |
1 | F |
-----
(D) 5 | |
4 | |
3 | F |
2 | D |
1 | B |
-----
(B) 5 | |
4 | |
3 | C |
2 | E |
1 | B |
-----
19. To reduce storage space and avoid bloated ( giant redundant ) inter-mediate relations, we can cross reference many fields in a query efficiently by: (Note: Assume all projects have no Where clause in them.)
(A) write many Join operations together, then do select
(B) write many Join operations together, then do Project
(C) Write many Join operations but put only Select in between them
(D) Write many Join operations but put Select and Project in between them as early as possible.
(E) Write many Join operations but Project in between; the order of Select has no effect on the space issue but Joins and Projects do. We leave Select for the end
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7 关于常量下面叙述错误有几个？
7. How many of the below are FALSE about constants?
他可能出现在赋值中,在左面，被赋值
I. They may occur on the left of := ( := 赋值 )
比较中
II. They may occur on the left of = ( = 比较 )
赋值给别人
III. They may occur on the right of :=
比较
IV. They may occur on the right of =
不改变值
V. They never change in value (inside the program during execution)
可以打印
VI. They may be printed (i.e. Used in a writeln)
可以改变
VII. They make code more easily modifiable if we needed to change something during code maintenance
在编译时可以改变
IX. They are converted to their actual value (in the program code) at compile time
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