Problem
I log into my mail account but do not know how to make underscore on the touch pad on my Samsung Galaxy Tab.
Solution
The touch pad, press the button to switch between letters and numbers "123" to the left of the spacebar
In numeric mode, press the "1 / 3". Underscore key appears in the first line of touch pad
There is also a trick to avoid having to do all the above:
Keep pressing the button to the right of the spacebar for two seconds and then the script in addition to the at sign, question mark and other symbols