Can a percent markup be 100% or 200%? what about a percent markdown?

Markup . . .

-- I buy a cabbage for $1.00 and put it on the shelf in my store. 
-- I mark it up 100% . . . I offer it for sale for $2.00
-- I mark it up 200% . . . I offer it for sale for $3.00 .

Markdown . . .

-- I buy a cabbage for $1.00 and put it on the shelf in my store. 
-- I mark it down 100% . . . I sell it for zero.  (I give it away.)
-- I mark it down 200% . . . I give you $1.00 to take it home with you.