Short answers, pulled from the story.
0, or zero, is a number representing an empty quantity. It is the additive identity of the integers, rational numbers, real numbers, and complex numbers, meaning adding or subtracting 0 leaves any number unchanged. Multiplying any number by 0 gives 0, and dividing by 0 is generally considered undefined in arithmetic.
A decimal place-value symbol for zero was developed in India. The Jain text Lokavibhaga, internally dated to AD 458, uses a decimal place-value system including a zero, and the earliest written symbol for the digit zero, a small circle, appears on a stone inscription at the Chaturbhuj Temple in Gwalior dated AD 876.
The Italian mathematician Fibonacci, also known as Leonardo of Pisa, was instrumental in bringing the system into European mathematics in 1202. He grew up in North Africa, where his father served at the customs house of Bugia, and credited the Modus Indorum, the method of the Hindus, transmitted earlier through Islamic scholars such as al-Khwarizmi.
The Greeks held a philosophical opposition to zero because their worldview rested on the idea that there is no void. Some asked how not-being could be, and the paradoxes of Zeno of Elea depend on this uncertain interpretation. Greek astronomers like Ptolemy nonetheless used a zero symbol in the Almagest by AD 150 for eclipse calculations.
The word zero reached English via French zero from Italian zero, a contraction of the Venetian zevero, traceable to the Arabic sifr, which meant empty in pre-Islamic times. Sifr came to mean zero when used to translate the Indian shunya, and the earliest known use of zero in English literature dates to 1598.
Computers store information in binary using only the symbols 0 and 1, where they can represent the absence or presence of electrical current. Zero often represents the Boolean value false, marks the end of a string in C, and serves as the null pointer. Languages like LISP introduced zero-based array indexing in the late 1950s, and the Unix epoch begins the midnight before the first of January 1970.