Ahh great thanks!

Draw function is a kind of " for loop " which runs at the speed of 1000 times per sec ( 1000 frames per sec) for infinite times so when you write a "for loop" inside a draw loop then this "for loop" runs completely in each frame so basically for loop runs completely 1000 in a sec. 

so for every n ----> i will print 1 to 100 means

when 

n =1 --> i will print completely 1,2,3,4,5,6.......100 ; 

n =2 --> i will print completely 1,2,3,4,5,6.......100 ; 

n =3 --> i will print completely 1,2,3,4,5,6.......100 ; 

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. n = forever --> i will print completely 1,2,3,4,5,6.......100 ;