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What is the difference between local variables and global variables of a C++ function?
What is the difference between local variables and global variables of a C++ function?
Apr 19, 2024 pm 03:42 PM
C The difference between local variables and global variables: Visibility: Local variables are limited to the defining function, while global variables are visible throughout the program. Memory allocation: local variables are allocated on the stack, while global variables are allocated in the global data area. Scope: Local variables are within a function, while global variables are throughout the program. Initialization: Local variables are initialized when a function is called, while global variables are initialized when the program starts. Recreation: Local variables are recreated on every function call, while global variables are created only when the program starts.
Local variables and global variables of C functions: big difference
In C, there are important differences between local variables and global variables. Understand these The distinction is critical to writing efficient, maintainable code.
Local variables
- are defined within a function and are only visible within the function scope.
- Created when the function is called and destroyed when the function returns.
- Local variables will be recreated every time the function is called.
Sample code:
void myFunction() {
int localVariable = 5; // 局部變量
// ... 使用 localVariable
}
int main() {
myFunction();
// localVariable 無法訪問，因為它不在 main() 函數(shù)的范圍內(nèi)
}Global variables
- are defined outside the function and are visible throughout the entire program.
- Created when the program starts and destroyed when the program terminates.
- Global variables are visible to all functions in the program.
Sample code:
int globalVariable = 10; // 全局變量
void myFunction() {
// ... 使用 globalVariable
}
int main() {
// ... 使用 globalVariable
}Difference
| Features | Local variables | Global variables |
|---|---|---|
| Visibility | Limited to the function in which they are defined | Entire program |
| Life cycle | During function call | During program running |
| Memory allocation | On the stack | In the global data area |
| Scope | In the function | In the entire program |
| Initialization | When the function is called | When the program starts |
| Recreate | Every time the function When called | Only when the program starts |
Actual case
Examples of local variables
In the following example , the local variable name is only used within the greet() function, and is recreated each time the function is called:
void greet(std::string name) {
std::cout << "Hello, " << name << "!" << std::endl;
}
int main() {
greet("John");
greet("Mary"); // 局部變量 name 將重新創(chuàng)建
}Example of global variables
In the following example, the global variable g_count is visible program-wide and is updated every time the function is called:
int g_count = 0; // 全局變量
void incrementCount() {
g_count++;
}
int main() {
incrementCount();
std::cout << "Count: " << g_count << std::endl; // 輸出 1
incrementCount();
std::cout << "Count: " << g_count << std::endl; // 輸出 2
}The above is the detailed content of What is the difference between local variables and global variables of a C++ function?. For more information, please follow other related articles on the PHP Chinese website!
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