http://www.gaw.ru/pdf/Maxim/dc-dc/MAX756-MAX757.pdf
What do the notation lines pin 1 SHDN mean. Also there in a line on pin 2 on 5 for 3/5. How do i set 5 and how do I set 3? I heard somewhere that these lines over the numbers regard float or pullup resistors, but I have no clue what these are.
SHDN = shutdown input signal.
Lines over the pins mean "active low", so you pull pin 1 low for shutdown,
and pin 2 low for 5V output.
Sometimes you need to use an external pullup R on input pins, and
sometimes they have internal pullups inside the chip to pull them high
if the inputs are floating. The chip spec sheet will indicate which.
Doe low mean ground? and high mean Vin?
In general, yes, but the spec sheet always puts ranges in the input
voltages.