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1. What does portability mean for programming?

In programming, portability refers to writing programs that can run on different computer systems or operating systems without much modification or tweaking of the code. This means that programs can be ported to different hardware and software environments without much customization or modification.

To achieve portability, programmers usually need to use portable programming languages ​​(such as C, C++, and Java) and standard libraries, and follow specific programming specifications and best practices. They also need to avoid platform-specific code and functionality, and use cross-platform APIs such as POSIX for platform-specific functionality.

By achieving portability, programmers can reduce the effort of rewriting and debugging code on different platforms, improve development efficiency, and at the same time provide a wider range of users and audiences.

2. Explain what is the difference between a source code file, an object code file, and an executable file?

In programming, source code files, object code files, and executable files are different file types with the following differences:

1. Source Code Files: Source code files are raw code files written by programmers, usually in a high-level programming language. Source code files are usually saved with a specific file extension (such as .c, .cpp, .java, etc.) and contain information such as the logic and algorithms of the program, variable and function definitions, and so on. Source code files cannot be executed directly, and need to be compiled and linked to generate executable files.

2. Object code file: An object code file is an intermediate file generated after the source code file is processed by a compiler and an assembler. Object code files contain machine language instructions and data, but have not yet been linked into an executable file. Object code files are usually saved with a specific file extension such as .o, .obj, etc., and can be cross-compiled on different platforms.

3. Executable file: An executable file is the final file generated after the object code file is processed by the linker, which contains instructions and data that the computer can directly execute. Executable files are usually saved with a specific file extension (such as .exe, .app, etc.) and can run on a specific operating system and hardware platform.

Generally speaking, the source code file is the high-level language code file written by the programmer, the object code file is the intermediate file generated by the compiler and assembler, and the executable file is the final file processed by the linker. Executable files are files that can be directly executed by a computer, and source code files and object code files need to be compiled and linked to generate executable files.

3. What are the 7 main steps of programming?

The main steps of programming can be summarized in the following seven steps:

1. Requirements analysis: First of all, programmers need to clarify the requirements of the program, understand the needs of users and the functions to be realized by the program. This stage needs to communicate with users or customers to ensure that the design of the program is consistent with the requirements.

2. Design: On the basis of requirements analysis, programmers need to design the structure and algorithm of the program, and determine the modules, functions, and data structures of the program. The design can adopt numerous design patterns and methodologies, aiming at improving the maintainability and extensibility of the program.

3. Coding: After the design is completed, the programmer needs to convert the design into executable source code. During the coding process, programmers need to choose the appropriate programming language and tools, and follow programming specifications and best practices to ensure the quality and readability of the code.

4. Testing: After coding is complete, the programmer needs to test the program to ensure that the program works properly and meets the requirements and design requirements. Testing can use various methods such as unit testing, integration testing, and system testing, aiming at discovering and fixing bugs and defects in the program.

5. Debugging: If testing finds bugs and defects, programmers need to debug to find the root cause of the problem and make fixes and optimizations to the code.

6. Deployment: After testing and debugging is complete, the programmer needs to deploy the program to the production environment. During this process, programmers need to configure and install to ensure that the program can run stably in the production environment.

7. Maintenance: After the program is deployed to the production environment, programmers need to perform maintenance to ensure that the program can run stably for a long time and meet the needs of users. Maintenance can include tasks such as code optimizations, bug fixes, security updates, and more.

4. What is the task of the compiler?

A compiler is a program that converts high-level language source code into object code or executable code. The main tasks of the compiler include the following aspects:

1. Lexical analysis: The compiler first needs to perform lexical analysis on the source code, decomposing the source code into individual lexical units or tokens. This process usually includes steps such as tokenization, parsing, and word segmentation.

2. Parsing: The compiler next needs to parse the tokens to determine the structure and syntax of the source code. This process usually includes steps such as building an abstract syntax tree, parsing grammar rules, and checking for grammar errors.

3. Semantic analysis: After the compiler completes the syntax analysis, it needs to perform semantic analysis on the source code to determine the meaning and behavior of the program. This process usually involves steps such as type checking, scope analysis, and symbol table processing.

4. Code Generation: After completing the semantic analysis, the compiler needs to convert the source code into object code or executable code. This process usually includes steps such as code optimization, instruction selection, register allocation, and code generation.

5. Object code generation: After code generation is done, the compiler needs to convert the object code into executable code or library files. This process usually includes steps such as linking, relocation, and library file generation.

In general, the task of the compiler is to convert high-level language source code into object code or executable code, and complete related tasks such as error checking, code optimization, and object code generation. Compiler is one of the important tools and infrastructure of programming, it is a key component of converting high-level language into machine code.

5. What is the task of the linker?

A linker is a program that combines object code files and library files into an executable or shared library. The main tasks of the linker include the following aspects:

1. Symbol analysis: The linker first needs to analyze the symbols in the object code file and library file to determine the address and size corresponding to each symbol. Symbols can be variables, functions, constants, etc.

2. Symbol relocation: After the symbol resolution is completed, the linker needs to relocate the symbols in the object code file and library file to modify the address of the symbol to the correct value. This process usually includes steps such as modifying absolute addresses, relative addresses, and relocation tables.

3. Symbol merging: After completing symbol relocation, the linker needs to merge the symbols in the object code file and library file to ensure that each symbol has only one definition. Symbol merging can avoid problems such as symbol conflicts and duplicate definitions.

4. Library file link: After symbol merging is completed, the linker needs to link the library file into the object code file to add the library functions and symbols required by the program to the program. This process usually includes two ways of static linking and dynamic linking.

5. Executable file generation: After linking the library file, the linker needs to combine the object code file and the library file into an executable file or a shared library. The generated executable file can be run directly in the operating system, and the shared library can be shared and used in other programs.

In general, the task of the linker is to combine object code files and library files into executable files or shared libraries, and complete multiple tasks such as symbol resolution, symbol relocation, symbol merging, and library file linking. The linker is one of the important tools and infrastructure of programming. It ensures that the program can run normally and can use the required library functions and symbols.