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The usage methods of symbols in C language cover arithmetic, assignment, conditions, logic, bit operators, etc. Arithmetic operators are used for basic mathematical operations, assignment operators are used for assignment and addition, subtraction, multiplication and division assignment, condition operators are used for different operations according to conditions, logical operators are used for logical operations, bit operators are used for bit-level operations, and special constants are used to represent null pointers, end-of-file markers, and non-numeric values.

In C, the char type is used in strings: 1. Store a single character; 2. Use an array to represent a string and end with a null terminator; 3. Operate through a string operation function; 4. Read or output a string from the keyboard.

In C language, special characters are processed through escape sequences, such as: \n represents line breaks. \t means tab character. Use escape sequences or character constants to represent special characters, such as char c = '\n'. Note that the backslash needs to be escaped twice. Different platforms and compilers may have different escape sequences, please consult the documentation.

The difference between multithreading and asynchronous is that multithreading executes multiple threads at the same time, while asynchronously performs operations without blocking the current thread. Multithreading is used for compute-intensive tasks, while asynchronously is used for user interaction. The advantage of multi-threading is to improve computing performance, while the advantage of asynchronous is to not block UI threads. Choosing multithreading or asynchronous depends on the nature of the task: Computation-intensive tasks use multithreading, tasks that interact with external resources and need to keep UI responsiveness use asynchronous.

In C language, the main difference between char and wchar_t is character encoding: char uses ASCII or extends ASCII, wchar_t uses Unicode; char takes up 1-2 bytes, wchar_t takes up 2-4 bytes; char is suitable for English text, wchar_t is suitable for multilingual text; char is widely supported, wchar_t depends on whether the compiler and operating system support Unicode; char is limited in character range, wchar_t has a larger character range, and special functions are used for arithmetic operations.

In C language, char type conversion can be directly converted to another type by: casting: using casting characters. Automatic type conversion: When one type of data can accommodate another type of value, the compiler automatically converts it.

char and unsigned char are two data types that store character data. The main difference is the way to deal with negative and positive numbers: value range: char signed (-128 to 127), and unsigned char unsigned (0 to 255). Negative number processing: char can store negative numbers, unsigned char cannot. Bit mode: char The highest bit represents the symbol, unsigned char Unsigned bit. Arithmetic operations: char and unsigned char are signed and unsigned types, and their arithmetic operations are different. Compatibility: char and unsigned char

The char array stores character sequences in C language and is declared as char array_name[size]. The access element is passed through the subscript operator, and the element ends with the null terminator '\0', which represents the end point of the string. The C language provides a variety of string manipulation functions, such as strlen(), strcpy(), strcat() and strcmp().