ZeroBased

Zerobased, or zero-based indexing, is a convention in which the first element of an indexed sequence is assigned the index 0. In many programming languages and data structures, positions within arrays, lists, strings, and other sequences are referred to by nonnegative integers starting at 0.

The rationale for zerobased indexing traces back to memory addressing and pointer arithmetic. The offset from the base address of a sequence often maps directly to the element’s index, which simplifies calculations and implementation. In addition, many language designs apply end-exclusive ranges in loops and slices, aligning naturally with zero-based indices.

Languages that use zerobased indexing include C, C++, Java, Python, JavaScript, Go, and Rust, among many others. Some languages or domains employ different bases or provide alternative views: Lua and MATLAB, for example, use one-based indexing in most contexts, while others offer mixed or optional indexing schemes. Even within a language, certain APIs may present 1-based counts for user-facing data while internally using zerobased indices.

Advantages of zerobased indexing include straightforward address computation, consistency with pointer arithmetic, and support for end-exclusive ranges, which simplifies loop and slice construction. Disadvantages include potential off-by-one errors when interfacing with human users or external systems that use one-based counting, a steeper initial learning curve for beginners, and occasional confusion when converting between counts and indices.

Related concepts include end-exclusive ranges and one-based indexing. Zerobased is a widely used default in many contemporary languages, shaping common patterns for iterating and accessing sequence elements.

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