Appending

Appending is the operation of adding data to the end of an existing sequence, stream, or structure. It is used to extend content while preserving the original portion. Appending differs from inserting at arbitrary positions or simply concatenating two sequences; in many contexts it implies growth at the tail, with performance and semantics that depend on the underlying data structure and implementation.

In programming languages, append adds an element to the end of a collection or characters to a string. For strings, many languages treat them as immutable, making repeated appends costly unless a specialized builder or join pattern is used. Mutable collections typically provide an append method that runs in amortized constant time for dynamic arrays or in constant time for linked lists with a tail reference. Append operations are fundamental for building sequences incrementally during iteration or data processing.

In file systems and I/O, appending to a file means writing data at the end of the existing file. Opening in append mode ensures new bytes are added after the current end, and operating systems may buffer writes; concurrent writers may require synchronization to avoid interleaving. Atomic append guarantees can vary by platform and file system, influencing durability and consistency guarantees.

In databases and logs, append-only designs store new records at the end of a log or table, supporting fast sequential writes and straightforward recovery, auditing, and replication. Deletions or random access typically require auxiliary structures, indexing, or compaction to maintain performance and data integrity.

Common considerations include atomicity, durability, concurrency, and platform differences. Choosing the right data structure or storage mode for appending depends on performance requirements, failure semantics, and how quickly existing content must remain accessible.