Call by address意思

"Call by address" is a term used in programming languages to describe a method of calling functions or procedures that involves passing the address of a variable or expression to the function rather than the value of the variable or expression itself. This technique is also known as "call by pointer" or "call by reference" because it allows the function to modify the variable directly, rather than creating a local copy of the variable.

Here's how it works:

1. When a function is called by address, the address of the variable is passed as an argument to the function.
2. Inside the function, the argument is used as a pointer to the variable in the calling function's scope.
3. The function can then modify the value of the variable by dereferencing the pointer and assigning a new value to it.
4. When the function returns, the modified value of the variable is visible to the calling function.

Call by address is a powerful technique that can save memory and time by avoiding the need to copy large data structures, but it also requires caution because it allows functions to modify variables that were not intended to be changed.

In many programming languages, such as C and C++, call by address is achieved using pointers. In other languages, such as Python and Java, pass-by-reference is achieved using references or object semantics, which are similar in concept but may have different syntax and semantics.