What should be considered when using global variables in the C language?

When using global variables in C programming, it is important to keep in mind the following points:

1. The scope of global variables: Global variables have a scope of the entire program and can be accessed in any function. However, when using global variables in different files, the keyword “extern” needs to be used for declaration.
2. Avoid naming conflicts: Global variables should be named in a way that does not overlap with other variables or functions to prevent confusion.
3. Initialization: global variables can be initialized at the time of declaration, otherwise they are automatically set to 0 or an empty value.
4. Storage location: Global variables are stored in the static storage area and their lifespan is consistent with the program’s runtime.
5. Modifiability: the value of global variables can be modified in any function, but attention should be paid to the visibility and thread safety of the variables.
6. Impact: Modifying global variables can affect the execution of the entire program and may lead to unexpected results. Therefore, it is important to use global variables cautiously and prefer using local variables whenever possible.
7. Memory usage of global variables: Global variables occupy memory, so it is important to monitor memory usage to prevent memory leaks or excessive memory consumption.

In conclusion, when using global variables, one must consider issues such as naming conflicts, visibility, thread safety, scope, and memory usage. Proper use of global variables can facilitate data sharing, but it is important to pay attention to these factors.