Simplify the given expression.

$1000\times 100-1000+4000÷200$

To simplify the given expression, we must follow the standard order of operations (often remembered as BODMAS/PEMDAS). This order dictates that we perform operations in the following sequence:
1. Division and Multiplication (from left to right)
2. Addition and Subtraction (from left to right)

The given expression is:

$1000\times 100-1000+4000÷200$

Step 1: Perform the multiplication and division first.

First, calculate the multiplication part:
$1000\times 100=100000$

Next, calculate the division part:
$4000÷200=20$

Step 2: Substitute these values back into the expression.

Now, replace the multiplication and division parts with their simplified results:

$100000-1000+20$

Step 3: Perform addition and subtraction from left to right.

First, subtract 1000 from 100000:
$100000-1000=99000$

Now, add 20 to the result:
$99000+20=99020$

Therefore, the simplified value of the expression is 99020.