Basic Number Theory for Problems on numbers in Aptitude

         Hi everyone, you may not get direct questions on this in any aptitude type test. But, by knowing this number system basics you can be able to solve some silly questions on numbers in some simple tests. So, Get your basics brushed up with this.
0,1,2,3,4,5,6,7,8,9 –    Digits

group of digits        –    Numbers

basic number theory for number problems

Natural numbers : 1,2,3,4,5,6,7,8,9,10,11………………….
Whole numbers : 0,1,2,3,4,5,6,7,8,9,10,11,12…………….
Integers: ………-4,-3,-2,-1,0,1,2,3,4………………….
        Positive integers : 1,2,3,4,5,6,7………….
        Negative integers : ………….-7,-6,-5,-4,-3,-2,-1
        Non positive integers : 0,-1,-2,-3,-4…….
        Non negative integers : 0,1,2,3,4,5,6…………………

0 is neither positive nor negative.