How do I find the place value of a number?

Question

How do I find the place value(hundreds,decimals,ones) of a number using modulus?
For instance;
var a = parseFloat(prompt("insert a number")),
b = a%100,
c = c%10;
document.write()...

Answer 1

For 1's place:
b=a%10

For 10's place:
a/=10
b=a%10

For 100's place
a/=100
b=a%10

And so forth

Answer 2

what is the slash for ?