In computer sciences, we use number systems when working with arrays, without a number system we would not be able to keep track of what is going on. Number systems are highly vital to security codes. Number theory is tightly linked to cryptography, which uses (in internet security mainly) modulus arithmetic and prime number factorization, important parts of number theory. This a free Mathematical calculator to convert or perform arithmetic operation of different types of number system such as DECIMAL, BINARY, OCTAL, HEXADECIMAL. This calculator can ADD, SUBTRACT, MULTIPLY, DIVIDE and Convert any DECIMAL, BINARY, OCTAL, HEXADECIMAL number. Features: =>Decimal to --> Binary, Octal, Hexadecimal =>Binary to --> Decimal, Octal, Hexadecimal =>Octal to --> Decimal, Binary, Hexadecimal =>Hexadecimal to --> Decimal, Binary, Octal Decimal => Addition, Subtraction, Multiplication, Division. Binary => Addition, Subtraction, Multiplication, Division Octal => Addition, Subtraction, Multiplication, Division Hexadecimal => Addition, Subtraction, Multiplication, Division