startIndex

startIndex is a numeric position indicating where to begin an operation within a sequence such as a string or an array. It is commonly used to extract, modify, or locate a subset of data.

In many languages indices are zero-based. When used with a second boundary (endIndex), it defines a range typically written as [startIndex, endIndex), where the end is exclusive.

Examples: In JavaScript, 'abcdef'.slice(2) yields 'cdef', and 'abcdef'.slice(1,4) yields 'bcd'. For arrays, arr.slice(1,3) returns elements at indices 1 and 2. Some environments support negative startIndex values, counting from the end.

StartIndex behavior varies by API. Some functions clamp out-of-range values to the nearest valid index; others may throw errors or produce empty results. Always consult the documentation to confirm whether startIndex is inclusive or exclusive, and how negatives are treated.

In data processing, startIndex marks where a scan or operation begins, interacting with length, endIndex, and offsets within data structures. It is a conceptual rather than a universal construct, so naming and semantics depend on the library.

See also endIndex, length, slice, substring, offset, range.