The while is an entry controlled loop statement. The test condition is evaluated and if the condition is true, then the body of the loop is executed. After execution of the body, the test condition is once again evaluated and if it is true, the body is executed once again. The process of repeated execution of the body continues until the test condition finally becomes false and the control is transferred out of the loop. On exit, the program continues with the statement immediately after the body of the loop.
With the help of do-while statement we can execute the body of the loop before the test is performed.
On reaching the do statement, the program proceeds to evaluate the body of the loop first. At the end of the loop, the test-condition in the while statement is evaluated. If the condition is true the program continues to evaluate the body of the loop once again. This process continues as long as the condition is true. When the condition becomes false, the loop will be terminated and the control goes to the statement that appears immediately after the while statement.