Computer Eng. Calculator

A calculator that supports some basics computer engineers operations, which are:
Add: +
Subtract: -
2 to pow: 2^
x to pow: x^
Logarithm base 2: log
Modulus: %
Logical and: AND "&"
Logical or: OR "|"
Logical xor: XOR "⊕"

And also it supports 3 of a the very known bases (instantaneous transformation), which are:
Binary: BIN
Decimal: DEC
Hexadecimal: HEX

A keypad with 1,2,3,4,5,6,7,8,9,0,A,B,C,D,E, and F is provided to enter data.

To evaluate an expression, an equal "=" button is there to done the task.
To delete (backspace) a typo use "DEL" button.
To clear the screen from the whole input use "CLS" button.
To use the last answer found use "ANS" button.

NOTE:
1- All logarithm operations are rounded up.
(i.e. loglog .. logloglogn = ceil(log(log( .. log(log(log(n))) .. )))
2- Logarithm function only takes 1 input.
(e.g. in decimal: log64/3 = log(64)/3 = 2)
3- Arithmetical and Mathematical operations has higher priority than Logical operations.
(e.g. in binary: 1111 - 0011&0001 = 1100&0001 = 1101)
4- The maximum positive number for the result is 2,147,483,646, and if it is exceeded you will get an IntegerOverFlow error, and the minimum negative number of the result is -2,147,483,647, and if it is exceeded you will get an IntegerUnderFlow error.
5- If an input expression is written wrong, a Syntax Error will occurs.
(e.g. log+2, &/15).


For developer:
If you are using Java and you need to evaluate some mathematical expressions use "exp4j" library, it is a very simple tool.
Special thanks for "exp4j" creator(s).