Topic 1: Basics of Computer Networks
1.What is the definition of computer network?
Computer network refers to a computer system composed of communication equipment and different types of computers. It uses transmission media, such as cables, optical cables, wireless, etc., and communication protocols to realize information transmission and resource sharing between computers.
2. What is the difference between the intranet and the external network?
Intranet refers to the computer network within an organization, which is usually controlled by network security protection. The external network refers to the public Internet, the global network, which can be accessed by many people without any restrictions, and its risks are relatively high.
3. Briefly describe the five-layer structure of TCP/IP protocol?
The TCP/IP protocol is a set of protocols designed for the Internet. Its five-layer structure includes: physical layer, data link (link layer), network layer, transport layer and application layer. Each layer corresponds to a different protocol.
4.What are IP address and MAC address?
An IP address is a globally unique numerical address that identifies a computer or device on a network. The MAC address is a hardware address (Media Access Control Address), which is unique on the network and used to identify the network adapter. Basically, the adapter manufacturer presets the MAC address and cannot change it.
5. Please briefly describe the three-way handshake of the TCP protocol?
The TCP protocol uses a three-way handshake to establish a connection. The process is as follows:
(1) If host A wants to establish a connection with host B, it sends a SYN (SYNchronization) message to host B as a request.
(2) After receiving the request, host B replies with a SYN+ACK message to host A as a response.
(3) After receiving the response, host A sends a message containing ACK confirmation information to host B, and the connection is established.
6.What is the difference between HTTP and HTTPS?
HTTP (Hypertext Transfer Protocol) is a protocol used to transmit data, and its security is poor. HTTPS (Hypertext Transfer Protocol Secure) is based on the TLS/SSL protocol, adding security to HTTP, and its data transmission will be encrypted, making it more secure.
7. What is DNS? What is its function?
DNS (Domain Name System) is a network service used to convert domain names into IP addresses, making it easier for humans to remember domain names, effectively avoiding the use of long strings of numerical IP addresses, and improving network availability.
Topic 2: Operating System
1. What is an operating system? What are its main functions?
An operating system is a software that controls the operation of computer hardware and application programs. It is one of the most basic software of a computer system. Its main functions include: resource management, job management, file management, process management, and equipment management.
2. What is the difference between a process and a thread?
The process is the basic unit of program execution and the basic unit of resource allocation by the operating system. The thread is the execution unit within the process and is responsible for executing the program code in the process. Threads share the resources of the process, including address space, file descriptors, signal processing, etc., which can improve the efficiency of program running.
3. Please explain what is deadlock?
Deadlock refers to a system state that occurs when multiple processes concurrently access shared resources, that is, all processes are blocked and cannot continue to execute. Deadlock usually occurs when multiple processes compete for resources from each other, such as improper resource allocation or process scheduling algorithm errors.
4.What is the virtual memory of the operating system?
Virtual memory is a virtual memory technology of the operating system. It means that the computer system combines the memory space and the hard disk space to create a virtual memory space, which can manage memory resources more effectively and enhance the stability and performance of the system.
5. Briefly describe the state transition of the process?
There are three process states: ready state, execution state and blocking state. The status of the process will continue to change, and the conversion relationship is as follows:
(1) New state: When the process is first created, it is in the new state.
(2) Ready state: The process has been allocated all necessary resources and is waiting for the CPU to execute its instructions.
(3) Execution status: The instruction set is being executed.
(4) Blocking state: waiting for certain events to occur, such as I/O operations.
(5) Termination status: The process has completed its task, exited the program, or was killed by the operating system.
6.What are operating system interrupts?
The interrupt of the operating system means that during the running of the computer, the currently executing program issues an interrupt instruction, prompting the operating system to suspend the execution of the current program, execute other programs or handle other events. Interrupts are divided into hard interrupts and soft interrupts. Among them, hard interrupts are triggered by external devices, such as mouse and keyboard, while soft interrupts are internal operations of the computer, such as system calls.
7. What is a file system? What is its main function?
A file system is a program that manages files and directories in an operating system, including the creation, modification, and deletion of files. Its main function is to provide users with organization and access to files.
Topic 3: Database
1. What is a database? What is its main function?
A database is a way of organizing data. It is a collection of data that is structured and stored together and can be shared. The main function of the database is to facilitate data query and management, and to provide data support for informatization construction.
2. What is SQL? What are its main functions?
SQL (Structured Query Language) is a language used to manage and operate relational databases. Its main functions include: querying, inserting, updating and deleting data, creating and modifying table structures, and permission control.
3. What is the role of indexes in the database?
An index is a data structure in a database that is used to speed up data searches and queries. Indexes can reduce the number of data accesses and improve query efficiency, but they also increase the time and space overhead of update operations. Indexes are divided into clustered indexes and non-clustered indexes, and their application scenarios are different. You need to choose the appropriate index method according to the specific situation.
4. What is a transaction? What is the ACID of a transaction?
A transaction refers to a set of database operations that either all execute successfully or all fail. It is the basic unit of database operations. ACID refers to the four characteristics of transactions, namely atomicity, consistency, isolation and durability.
5. What is the locking mechanism of the database?
The locking mechanism of the database ensures data consistency when multiple users access it concurrently. Databases usually use row-level locks and table-level locks to protect the independence and security of data. In the case of high concurrency, the lock mechanism can effectively control read and write operations and avoid data errors and conflicts.
6.What is the role of views in the database?
A view is a logical table in the database, which is a result set composed of rows and columns of one or more tables. Its main function is to logically group and filter data, hide specific table structure information from users, and improve Ensure data security and readability.
7.What is a trigger in a database?
A trigger is a special object in the database that can automatically trigger user-defined logical behaviors when operations are defined on a database table, such as insert, update, or delete operations. Triggers can replace certain data processing in applications, increase data consistency and integrity, and are suitable for many business scenarios, such as auditing and logging.