Assume the availability of an existing class, icalculator, that models an integer arithmetic calculator and contains:
an instance variable currentvalue that stores the current int value of the calculator
and can be accessed and modified by any subclass.
methods add, sub, mul, and div

each method in icalculator receives an int argument and applies its operation to currentvalue and returns the new value of currentvalue. so, if currentvalue has the value 8 and sub(6) is invoked then currentvalue ends up with the value 2, and 2 is returned.

so, you are to write the definition of a subclass, icalculator2, based on icalculator. the class icalculator2 has one additional method, negate, that receives no arguments. the effect of negate is to reverse the sign of currentvalue. for example, if currentvalue is zero, there is no change, if it is -22 then it becomes 22, if it is 100 it becomes -100. furthermore negate returns the new value of currentvalue.

Data is processed, stored, and transmitted as a series of 1s and 0s. each 1 or 0 is called a(n) . a series of eight 0s and 1s, called a(n) , represents one character—a letter, number, or punctuation mark. data becomes when it is presented in a format that people can understand and use. digital signals are represented by two different , such as +5 volts and +.2 volts. digital data can also take the form of light and dark spots etched onto the surface of a cd or the positive and negative orientation of particles on the surface of a hard disk. data consists of numbers that might be used in arithmetic operations. it can be represented digitally using the number system. data is composed of letters, symbols, and numerals that are not used in arithmetic operations. computers represent this type of data using , ebcdic, unicode, or utf-8. data is quantified using terms such as or kibibyte (1024 bytes), and prefixes such as or mebi (1,048,576), and giga or (1,073,741,824). to reduce file size and transmission times, digital data can be compressed. compression provides the means to compress data and reconstitute it into its original state. compression throws away some of the original data during the compression process. compressed files usually have at the end of the file name and are represented with special icons. these files have to be or unzipped before you can view the data they contain.