What is the most basic logical element of data?

Answer 1

The most basic logical element of data is the binary digit, or bit, which can represent the numeric value 0 (the bit is unset) or 1 (the bit is set), which can subsequently represent any opposing concept, such as true or false, yes or no, black or white, positive or negative, etc.

However, computer systems do not permit the storage of a single bit because a single bit cannot be addressed in memory. Every memory address represents a group of bits known as a byte (8 bits), thus a boolean value (a value that has only two possible states, such as true or false) is typically composed of 8 bits where the binary value 00000000 (no set bits) is regarded as being false while any other combination of bits (a non-zero value) is regarded as being true. Typically the binary value 11111111 (which is decimal -1 in signed notation) is regarded as being true but any non-zero value is also regarded as being true.

In order to conserve memory, programmers will often combine several boolean values into a single value, such that each individual bit represents something different. Thus a single byte can effectively store up to 8 individual boolean values. In order to determine the state of any one bit, the programmer simply tests the combined bits against the bit-value he's actually interested in. For instance, to test if bit 3 is set (the fourth least-significant digit, from the right), the programmer will logically AND the combined bits with the value 23, which is 00001000 in binary (8 decimal). If the result is non-zero then bit 1 is definitely set, otherwise it is not.