What is the function of the following code?

Scanner scan $=$ new Scanner$($System$.$in$)$;$$

System.out.print$("$Enter an integer: $")$;$$

number $=$ scan.nextInt$()$;$$

while $($number $<=0)$

$\{$

$$System$.$out.print$("$That number was not correct."$)$;$$

$$System$.$out.print$("$Enter another integer: $")$;

$$number $=$ scan.nextInt$()$;

$\}$

a$.$

Makes sure the input is negative

b$.$

Makes sure the input is positive

c$.$

Makes sure the users inputs a number

d$.$

Makes sure the user inputs a number without error