how i could make calculator inc++ that do calculation in regular interval
like it do calculation as same as the calculator

You can make a menu where the user picks a an operation. Depending on the choice a function will be called to implement that specific operation.
Functions can include add, subtract, multiply, divide, powers of exponents, square root, etc.
You can ask the user how many numbers they want to manipulate (i.e. add, subtract.........). Then perhaps, store the numbers in an array and perform the specific operation.
I'm sure someone else can weigh in with a better abd more efficient method.