allzero

Allzero is a term used in computing to describe a data pattern in which every bit is zero. It is commonly used to denote a block of memory or a field that contains only zeros, and is sometimes written as all-zero or allzero.

In software and hardware, all-zero data serves as a baseline state for initialization, testing, and secure memory handling. Allocators may fill newly allocated memory with zeros, a practice known as zero-initialization, to prevent leakage of previous data. In cryptography and security contexts, all-zero values are usually avoided for keys, nonces, or initialization vectors because they can create predictable, exploitable patterns.

In data formats and communications, an all-zero block may appear as padding, a delimiter, or a reserved placeholder in certain protocols. Some file systems use zero-filled sectors to indicate unused space, while some network protocols employ zero blocks to mark the end of a message stream.

In programming, routines exist to check whether a buffer is all zeros or to transform a buffer into an all-zero state. Efficient implementations may use vectorized instructions or specialized memory operations to test or clear large memory areas quickly.

Related concepts include zero, zeroization, memory initialization, and padding.