[The following operations are in command mode]
(up/down) full page flip ctrl-f ctrl-b
f is forward b is backword
(up/down) turn half page
ctrl-d : d=down
ctrl-u : u=up
(up/down) turn a line
ctrl-e ctrl-y
zz makes the row where the cursor is located in the center of the screen
zt Make the row where the cursor is located on the top row of the screen t=top
zb makes the line where the cursor is located at the bottom line of the screen b=bottom