Small knowledge, big challenge! This article is participating in the creation activity of “Essential Tips for Programmers”.

🌴 Data structure

Which of the following statements about linear tables is wrong? (Beijing Jiaotong University Postgraduate Entrance Exam)

A. Linear tables are stored sequentially and must occupy A contiguous storage unit. B. Linear tables are stored sequentially to facilitate insertion and deletion. D. Linear tables use linked storage to facilitate insertion and deletionCopy the code

parsing

Answer: B

📢 Common sense: Linear table inserts and deletes move a large number of elements, which is relatively inefficient.

🌳 Computer network

Which of the following is a medium access control method for Fast Ethernet ___

A. SMA/CD B. token bus C. token ring D. 100VG-anyLANCopy the code

parsing

Answer: A,

📢 Ethernet uses THE CSMA/CD protocol to control bus access.

CSMA/CD is carrier sense multiple access with collision detection. Its working principle can be summarized in four sentences: “listen first and then send, listen while sending, stop collision, and send again after random delay”.

The specific process is as follows:

  1. When a node wants to send data, it checks the network to see if other nodes are transmitting, that is, it listens for channels that are free.
  2. If the channel is busy, wait until the channel is free.
  3. If the channel is idle, the node transmits data.
  4. While sending data, the node continues to listen to the network to make sure that no other node is transmitting data at the same time.
  5. If a collision is detected, that is, another node is sending data at the same time, the data is terminated and a congestion signal is sent to let all users know.
  6. After the sending is stopped, the exponential backoff algorithm is executed and the system returns to Step 1 after a random period of time.

🌵 Operating system

In the following statement, the wrong is ___ (2015年 考 题)

A. The operating system is capable of both multitasking and multiprocessing B. Multiprocessing is A subset of multitasking C. Multitasking refers to running multiple processes simultaneously on the same system at the same time. D. Multitasking can be performed on a computer with the same CPUCopy the code

parsing

Answer: B

📢 Multiprocessing refers to parallel execution, and multitasking refers to concurrent execution of multiple processes.

  • The operating system can support both concurrent execution and parallel execution.
  • Parallelism should be a true subset of concurrency.
  • C) Concurrent execution is the basic concept of running multiple processes in the system at the same time interval.
  • A CPU can use a multi-core architecture, which can realize parallel execution.

Concurrency is not really “simultaneous”, so the concepts of parallelism and concurrency will not be repeated here.

🌲 Computer composition principle

Every left shift of a digit is equivalent to multiplying the original digit by 2. In order to prevent overflow caused by the left shift operation, the prerequisite for the left shift of the complement is: its original most significant bit ___ (Harbin Engineering University, 2005)

A. 0 B. 1 C. Same D as the original sign bit. Different from the original sign bitCopy the code

parsing

Answer: C

When 📢 complement is expressed, 0 is the most significant bit, and 1 is the invalid bit. Therefore, when arithmetic moves to the left, 0 is lost in the most significant bit, and the result is wrong. Losing 1 will not have negative effect on the result.

C) it doesn’t matter if you drop 0 to the left.

The exercises come from @Wangdao Weibo

The analysis is written by myself, if there are any questions or mistakes, please comment.

I am Mancuoj, welcome to pay attention to me and my computer entrance examination column (≧∇ Blue)