According to structured partitioning in software engineering a program ______.

Structured (modular) design uses structural partitioning as a heuristic for achieving effective modularity: a program's module hierarchy (structure chart) is split along two independent axes. Horizontal partitioning divides the structure breadth-wise into separate branches for each major function — typically input, transformation/processing, and output — placed at the same level. Vertical partitioning distributes control top-down: higher-level modules make decisions while lower-level modules perform detailed processing and utility work.

Applying this definition to the stem: structured partitioning names exactly two orthogonal directions along which a program's structure is split — horizontal and vertical. No recognised structured-design technique defines a "diagonal" partitioning axis, so any option built around that word cannot represent the governing rule.

• The pairing "horizontally and diagonally" keeps one genuine axis (horizontal) but substitutes an axis that structured design does not define (diagonal) for the other.

• The pairing "vertically and diagonally" keeps the other genuine axis (vertical) but again substitutes the same non-existent "diagonal" axis.

• "Diagonally" on its own drops both genuine axes and keeps only the term that structured partitioning never defines.

Structural partitioning therefore requires splitting the structure along both real axes together — horizontal and vertical. Splitting breadth-wise across major functions limits how far a change's side effects propagate across unrelated branches, and splitting depth-wise confines the impact of a control-logic change near the top of the hierarchy — together giving modules that are easier to test, maintain, and extend.