Answer
Get a value for $x$
While ($x$ $\ne$ 999) do
$\ \ \ \ \ \ $ Set the value of a to $x^{2}$
$\ \ \ \ \ \ $ Print the value of $a$
$\ \ \ \ \ \ $ Set the value of b to $sin(x)$
$\ \ \ \ \ \ $ Print the value of b
$\ \ \ \ \ \ $ If x = 0 then
$\ \ \ \ \ \ $ $\ \ \ \ \ \ $ Print the error message $'$Cannot compute $1/x$$'$
Else
$\ \ \ \ \ \ $ $\ \ \ \ \ \ $ Set the value of c to $1/x$
$\ \ \ \ \ \ $ $\ \ \ \ \ \ $ Print the value of $c$
$\ \ \ \ \ \ $ Get a value for $x$
End of the loop
Stop
Work Step by Step
Get a value for $x$
While ($x$ $\ne$ 999) do
$\ \ \ \ \ \ $ Set the value of a to $x^{2}$
$\ \ \ \ \ \ $ Print the value of $a$
$\ \ \ \ \ \ $ Set the value of b to $sin(x)$
$\ \ \ \ \ \ $ Print the value of b
$\ \ \ \ \ \ $ If x = 0 then
$\ \ \ \ \ \ $ $\ \ \ \ \ \ $ Print the error message $'$Cannot compute $1/x$$'$
Else
$\ \ \ \ \ \ $ $\ \ \ \ \ \ $ Set the value of c to $1/x$
$\ \ \ \ \ \ $ $\ \ \ \ \ \ $ Print the value of $c$
$\ \ \ \ \ \ $ Get a value for $x$
End of the loop
Stop