Postgraduate entrance exam 408 includes data structure, computer network, computer composition principle and operating system four subjects, each of which is the content that programmers should focus on understanding and mastering.
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The data structure
Which of the following terms has nothing to do with the data storage structure ____
A. stack B. hash C. clue TREE D. bidirectional linked listCopy the codeAnswer and analysis
Answer: A,
🔊 First of all, we need to know that the storage structure is also the physical structure, which is the representation of the data structure in the computer. There are the following four structures:
Because the stack doesn’t tell you whether it’s sequential or chained, so that’s choice A.
Cue tree is the cueing of tree based on chain storage.
Conclusion: When we distinguish whether a structure is a physical structure, we should look at whether it has only one definition in the physical structure. A logical structure is proved when there are multiple definitions, such as stacks and queues, that can be stored sequentially or chained.
Computer network
The Ethernet switch establishes a forwarding table based on the self-learning algorithm. It learns addresses through ___.
A. Source AND destination MAC addresses in frames B. ARP C. Destination MAC address in the frame D. Source MAC address in the frameCopy the codeAnswer and analysis
Answer: D
🔊 Ethernet Switch (Switch) is a data link layer device. It is a multi-port bridge that can forward multiple frames.
It is a plug and play device, so its internal forwarding table is gradually built up through self-learning algorithms.
How it works: Detects the source and destination MAC addresses of data frames from the port and compares them with the forwarding table. If the MAC address of the data frame is not in the table, the source address is written into the forwarding table (option D) and the data frame is sent to the corresponding destination port.
Conclusion: The switch is self-learning based on source address and forwarding based on destination address.
Computer composition principle
A machine word length is 16 bits, memory is byte addressable, PC current value is 2000H, when reading a double word instruction, PC value is ____.
A. 2000H
B. 2004H
C. 2008H
D. 200AH
Copy the codeAnswer and analysis
Answer: B
🔊 machine word length 16 bits, double word length instruction is 32 bits, byte address is 4B, so read 2004H, select B.
The operating system
What is true of the following four statements about operating systems that support multithreading is ____.
A. Using multiple threads to improve CPU utilization B. Process is the basic unit of CPU scheduling C. Thread is the basic unit of resource allocation. Compared with using multi-process, using multi-thread can improve the running efficiency of programCopy the codeAnswer and analysis
Answer: A,
[D] multithreading is used to maximize the utilization of CPU resources.
After the introduction of threads, threads are the basic unit of CPU scheduling and allocation, but not the basic unit of owning resources. Processes are the basic unit of owning resources.