the do while is a special case of a while function in a programming language, where the predicate is evaluated at the end of the code block it executes.
so you usually have
Always do the first iteration, and then if the predicate is true reiterate.
So to simulate something like
set i to 0
do {
append i to text
i = i + 1
} while (i < 10)
+ system: every tick
-> system: set i to 0
-> text: append i to text
-> system: add 1 to i
+ system: while
+ system: i < 10
-> text: append i to text
-> system: add 1 to i
as you see a do while is merely a syntaxic sugar to avoid repeating some of the code you write.