what, lower, upper and
answer.in. If the input does not satisfy all the conditions,
an appropriate error message is produced and the user is prompted
to provide input. This process is repeated until a valid input value
is entered.read.and.check(message = "", what = numeric(), lower, upper, answer.in,
default)what gives the type of data to be read.answer.in, if supplied.default argument is
specified, a blank line is accepted as valid input and in this case
read.and.check returns the value of default.