The HP Computer Museum documents HP computers, including the company's early 2116 model.
ModalLogic
This modal logic playground lets users edit a model and evaluate formulas using selected truth values.
About ModalLogic
ModalLogic is a browser-based playground for modal propositional logic. Users build a model by adding states and transitions, set truth values for up to five propositional variables (p, q, r, s, t), and evaluate formulas against that model. Formulas use text notation: ~ for not, & for and, | for or, -> for implication, for equivalence, [] for necessity, and for possibility.
The page also includes a short explanation of modal logic, covering possible worlds, accessibility relations, and how necessity and possibility are interpreted. It notes that the app covers modal propositional logic only and does not include quantifiers (∀ and ∃).
Key features
- Add states to a model by clicking in an open space
- Add transitions between states by dragging from one state to another
- Choose between one and five propositional variables, labeled p through t
- Set each variable to true or false in a selected state
- Toggle reflexivity of a selected state
- Change a selected transition's direction to left, right, or both
Best for: Students and instructors in logic, philosophy, or computer science who want to explore modal propositional logic with a visual model.
Good for
- Lets users evaluate formulas on a graphical model of states and transitions
- Includes a brief explanation of modal logic concepts such as necessity, possibility, and accessibility
Watch out for
- Covers modal propositional logic only, without quantifiers
- Supports up to five propositional variables
ModalLogic at a glance
- Category
- Education & Learning › History & Humanities
- Type
- Website
- Pricing
- Not confirmed. Check the site
- Platforms
- Web
- Open source
- Not stated
- Last checked
- Oct 6, 2026 · Online when checked
- Listed
- Oct 5, 2026
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ModalLogic FAQ
How do I write necessity and possibility in a formula?
Use []A for necessity (box) and A for possibility (diamond).
Does the app support quantifiers?
No. The app covers modal propositional logic, which lacks quantifiers (∀ and ∃).
How do I connect two states in a model?
Drag from one state to another to add a transition. Select a transition and use L, R, or B to set its direction.
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