Reducing the use of global variables in C can be achieved by: 1. Using encapsulation and singleton patterns to hide data and limit instances; 2. Using dependency injection to pass dependencies; 3. Using local static variables to replace global shared data; 4. Reduce the dependence of global variables through namespace and modular organization of code.

Classes in Java inherit from Object class by default unless they are explicitly inherited. 1. The Java class is directly or indirectly inherited from the Object class. 2. Class inheritance is implemented through the extends keyword, and the interface is implemented through the implements keyword. 3. The subclass constructor calls the parent class constructor first, and pay attention to the call order. 4. Java does not support multiple inheritance, but similar effects can be achieved through interfaces. 5. Combination should be used as much as possible instead of inheritance, keep the inheritance level simple and reduce the degree of class coupling.

In C, the bit field is a structure member that specifies the number of bits, used to save memory and directly manipulate hardware. Example: structMyStruct{inta:2;intb:5;intc:1;}. The advantage of bit domains is memory savings, but there are cross-platform issues, access restrictions and assignments that require caution. Example of usage: structStateMachine{unsignedintpower:1;unsignedintmode:2;unsignedinterror:1;}. Performance recommendations include arranging bit fields by size, avoiding overuse and adequate testing.

The syntax of the trigonometric operator in C is condition?expression1:expression2, which is used to select and execute different expressions according to the condition. 1) Basic usage example: intmax=(x>y)?x:y, used to select the larger value in x and y. 2) Example of nested usage: intresult=(a>0&&b>0)?a b:(a==0||b==0)?a*b:a-b, used to perform different operations according to different conditions. 3) Error handling example: std::stringerrorMessage=(errorCode==0)?"Successful&quo

The usage of logical non-operator! in C includes: 1) Basic usage: inverse the Boolean value; 2) Conditional judgment: simplify the code, such as checking whether the container is empty; 3) Loop control: processing elements that do not meet the conditions; 4) Function return value processing: determine whether the operation has failed. Pay attention to potential pitfalls such as pointer processing and operator priority when using!, but it can help write more concise and efficient code.

Exceptions in Java are divided into three types: detected exceptions, unchecked exceptions and errors. 1. The detected exception needs to be processed or declared in the code, such as IOException. 2. Unchecked exceptions are caused by logical errors, such as NullPointerException, and do not require forced processing. 3. Errors such as OutOfMemoryError are usually unrecoverable.

Python is widely used in data science, web development, automation, finance, scientific computing and other fields. 1) Data Science: Use NumPy, Pandas, TensorFlow and other libraries to process data and build models. 2) Web development: Django and Flask frameworks quickly build websites. 3) Automation: Write scripts to automate tasks. 4) Finance: Quantopian and Zipline are used for quantitative transactions. 5) Scientific Computing: SciPy and Matplotlib are used for data analysis and visualization. Python's simplicity and readability make it ideal for multiple fields.

Implementing an efficient and flexible logging system in C can use the following steps: 1. Define log classes and process log information at different levels; 2. Use policy mode to achieve multi-objective output; 3. Ensure thread safety through mutex locks; 4. Use lock-free queues for performance optimization. This can build a log system that meets the needs of actual application.