The diagrammatic representation of an algorithm is

An algorithm is a step-by-step set of instructions for solving a problem, and it can be represented in more than one way: written out in structured, code-like sentences, or represented visually. The visual, diagrammatic method uses standard shapes, such as an oval for start and end points, a rectangle for a process step, and a diamond for a decision point, all connected by arrows that show the order in which steps are carried out. This diagrammatic representation of an algorithm is called a flowchart, and it lets someone follow the logic of an algorithm visually without reading detailed written instructions.

Pseudocode also represents an algorithm's logic, but it does so through structured, plain-language statements written in lines of text resembling programming code, not through shapes and diagrams. Code refers to the actual instructions written in a specific programming language that a computer can execute, which is a textual, executable representation rather than a diagrammatic one. Graphics is simply a general term for visual images and does not refer to any structured method of representing an algorithm's logical steps.

When a question specifically asks for the "diagrammatic" representation of an algorithm, that phrasing should immediately point to flowcharts, since pseudocode and code are both text-based rather than diagram-based.