Lossy compressors don't have the same constraints as a lossless compressor. If you data your input, compress it, and then decompress it, the output is not identical to the input. This allows the compressor to potentially compress the data far more than even the ideal lossless compressor hypothesized above.
The question mark (?), also known as the interrogation point, query, and eroteme, is a punctuation mark that indicates an interrogative clause, or phrase in many languages. The question mark is not used for indirect questions.
The use of the phrase pound sign to refer to this symbol is found from 1932 in U.S. usage. Before this time, and still outside the U.S., the term pound sign was used to refer to the pound currency symbol (Â£) or the pound weight symbol (lb). An alternative theory is that this name arose from the fact that character encodings used the same code for both the number sign and the British pound sign Â£.