1.2.3—System diagrams
- Syllabus
- First assessment 2026
- Objective
- 1.2.3
- Level
- HL
Make Every Arrow Point the Right Way
A systems diagram uses boxes for storages and arrows for directional flows; an input crosses into the boundary and an output crosses out.
Ask ‘what moves, from where to where?’ before drawing the arrowhead. Direction is part of the meaning, not decoration.
A tank is the storage; the supply arrow points into it and the drain arrow points out.
A directional transfer of water; reverse the arrow only if the flow actually reverses.
An arrow is not merely a connection; its head must match the movement.