1One asterisk: * 2 3One underscore: _ 4 5Two asterisks: ** 6 7With spaces: * * 8 9Two underscores __ 10 11with spaces: _ _ 12 13three asterisks: *** 14 15with spaces: * * * 16 17three underscores: ___ 18 19with spaces: _ _ _ 20 21