In the programming language C++, why is it that we write x=x+y instead of y=x+y?

 In the programming language C++, the statement "x = x + y" assigns the value of the expression "x + y" to the variable "x". This statement updates the value of "x" by adding the value of "y" to it.

On the other hand, if we were to write "y = x + y", it would assign the value of "x + y" to the variable "y". This statement updates the value of "y" by adding the value of "x" to it.

The order in which we write the variables in the assignment statement matters because it determines which variable is updated with the new value. In the statement "x = x + y", the variable "x" is updated with the new value, while in "y = x + y", the variable "y" is updated with the new value.

The choice of which variable to update depends on the context and requirements of the program. In many cases, it is more appropriate to update the value of one variable rather than another, depending on the specific task or computation being performed. Therefore, it is important to understand the order in which variables are written in assignment statements, and to choose the appropriate variable depending on the requirements of the program.