Interview Guide-database-Operating System-Computer Network

I. Database.

1. A database is a software system that stores and manages data according to the data structure. DB

2. Database Management System: Software System for database management. DBMS

3. What is the design paradigm of relational databases? There are 6 types: 1-5 paradigm + bcnf. Generally, we only need to satisfy the first three scopes. If we are allowed, we should pursue a higher paradigm.

First paradigm: requirements are the basic requirements of relational databases. E-R relationships. Make sure that the values in the column cannot be repeated.

Second paradigm: each row must be able to be divided by a unique region.

Third paradigm: the table's non-primary key columns must not be dependent on each other. (Reduce data redundancy)

4. What is a database thing? (I .e. atomicity)

: Atomicity, consistency (modification must be consistent), isolation (independence between things does not affect each other), continuity (once a thing is committed, changes to the database data are permanent)

A transaction refers to a sequence of database operations when a user performs database operations. All the operations in the sequence are either executed or not executed. Each operation is an integral whole and cannot be separated.

5. Which database models are available:

Hierarchical Model, mesh model, and relational model.

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Operating System: a software system used to manage hardware, software, and data resources of a computer system, control program running, provide operation interfaces, and provide support for other application software.

1. He is the first level of system software closest to the computer hardware.

2. The minimum scheduling unit of the operating system is: thread.

3. The minimum operating system resource unit is process.

4. multithreading is mainly used to take advantage of CPU time and run multiple tasks in a process at the same time.

5. Differences between processes and threads:

1) a program has at least one process and at least one thread.

2) A process has an independent memory unit during execution, while multiple threads share the memory of the process.

3) The process can run independently, but the thread cannot be executed independently. It must be dependent on the process. The application that uses the process provides multiple thread execution control.

6. How to implement multi-threaded programming?

Thread Synchronization can be achieved through critical sections, mutex volumes, semaphores, and other methods.

7. Advantages of multithreading: 1. Multi-task 2. Improve Execution efficiency and processing capability. Disadvantages: scheduling problems when encountering dedicated resources.

8. Memory and Job Scheduling:

A job is an application. Job Scheduling mainly refers to how the system processes the running sequence of jobs when multiple jobs are running.

9. Memory Management Mode: seven modes are available: no management mode, single partition, fixed partition, variable partition, page, segment, and segment page. Currently, page management is most commonly used.

1. common Job Scheduling Algorithms: 1. service algorithm first 2. shortest job priority algorithm: Priority Assignment processor for jobs with short execution time. top Response Ratio Priority Method 4. the priority-based scheduling algorithm.

2. Job 4 Status: 1. Entering status 2. Backup status 3. Running status 4. Completion status

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Computer Network

1. What is the OSI Layer-7 model? (Referred to as: Open System Interconnection Reference Model)

Bottom-up: physical layer, data link layer, network layer, transmission layer, Session Layer, presentation layer, and application layer.

2. TCP/iPlayer 4 network structure: application layer, transmission layer, Internet layer, and network interface.

3. TCP/IP combines the Session Layer and presentation layer in OSI into the application layer, and combines the data link layer and the physical layer in OSI into the network layer.

4. what is the TCP/IP protocol: the most basic protocol for the Internet, which defines how idea devices connect to the Internet and how data is transmitted between them, TCP/IP is actually a set of protocols, including hundreds of various functional protocols.

5.