In C and C++, variables are used to store data values in a program. A variable must be declared before it can be used in a program, and it can also be initialized with a value at the time of declaration. Here are some examples of variable declarations and initializations in C and C++:

int x; // Declares a variable x of type int

int x = 10; // Declares a variable x of type int and initializes it with the value 10

int x, y, z; // Declares three variables x, y, and z of type int

int x = 10, y = 20, z = 30; // Declares three variables x, y, and z of type int and initializes them with the values 10, 20, and 30, respectively

In C and C++, variables can be declared and initialized in a single statement, or they can be declared and initialized separately. It is also possible to initialize a variable with an expression or a function call. For example:

int x = 5 + 10; // Initializes x with the value 15

int y = max(10, 20); // Initializes y with the value returned by the max function
Overall, variable declarations and initializations are an important concept in C and C++ programming, and they are used to store and manipulate data values in a program.