Last Updated: April 18, 2026

Introducing

C3 — successor to CADD/200-300

From the team that built the 2D CAD validated at Hughes Aircraft Space & Communications Group for satellite microwave design.

Now native on Apple Silicon. Perpetual license. No subscription. Ever.

Native macOS No Cloud Required One-Time Purchase 43 Years of Heritage
Request Private Access & Schedule a Demo

One-time purchase — no subscription, no recurring fees, ever

• Native macOS • Apple Silicon • No Cloud • No Subscription • Your Files, Your Drive
See C3 in 60 Seconds
Draw · Dimension · Export · Print — video coming soon
CADD300 Modern application screenshot showing a complex drawing with tool menus and layer panel
CADD300 Modern PCB design with Gerber RS-274X export dialog, layer mapping, and multi-layer transparency view of a printed circuit board

PCB design with Gerber RS-274X export — multi-layer transparency view, layer mapping, and one-click fabrication output

CADD300 Modern Layout/Paperspace showing six viewports of the MPC-1 schematic at different scales on a single 11x8.5 inch sheet

Layout / Paperspace — six viewports at different scales on a single sheet, with per-viewport layer groups

CADD300 Modern supports images inside drawings — photos of electronics, motorcycles, architecture, and construction embedded directly in a CAD drawing with Files Options menu showing import and export capabilities

Embed photos and images directly inside drawings — full import, scaling, rotation, and cropping support

Designed for Speed

Sidebar Menus + Voice Guidance + Hotkeys

Every feature is reachable from the always-visible sidebar — click a tool category and the panel shows all options, fields, and sub-tools. No hunting through nested dropdown menus. For experienced users, single-key shortcuts accelerate everything: L for lines, C for circles, B for boxes, T for text. Press ? for the complete hotkey reference.

Voice Guidance talks you through multi-step operations — “Click first point,” “Click second point,” “Click the side to offset.” Invaluable for learning complex tools and for hands-on-the-keyboard flow where your eyes stay on the drawing. One toggle switch in the main menu turns voice on or off.

CADD300 Modern HotKeys popup showing the 5-column layout of all keyboard shortcuts

Release Highlights

What’s New in Version 2.0

Five major capability upgrades shipped in v2.0: multiple independent drawing windows with cross-window drag-and-drop, spreadsheet-like tables on the canvas, multi-leader annotations, engineering dimension tolerances with ordinate dimensioning, and a full seven-mode snap system.

Multi Windows

C3 supports multiple independent windows — you can have two, three, or more drawings open at the same time, each in its own window, and drag primitives directly from one window to another.

Why Multi Windows Matters

Working with a single window means constantly saving, closing, opening, and copying between files. With multi windows, you can:

Tables & Spreadsheet

Embed fully interactive spreadsheet-like tables directly on the drawing canvas. Create any number of tables with as many rows and columns as your project requires. Click any cell to type data directly — Tab moves right, Enter moves down, just like a spreadsheet.

Multi-Leader Annotations

Place a text annotation with unlimited arrow leader lines pointing to features across the drawing. The text box goes down first, then click to add as many arrows as you need — each one exits from the nearest edge of the text box automatically. Drag the text box to reposition while all arrows maintain their target locations. Add or remove individual leaders at any time.

Dimension Tolerances & Ordinate Dimensions

Three tolerance modes for engineering dimensions: Symmetric (±0.005), Deviation (+0.010 / −0.003), and None. Tolerance values render as stacked fractions in smaller font after the dimension value.

Ordinate / Datum dimensions (Datum Horizontal and Datum Vertical) measure cumulative distance from a single reference point. Click the datum origin once, position the dimension line, then click as many target features as you need — each one creates a dimension showing the absolute distance from the datum. This is the equivalent of AutoCAD’s ordinate dimensioning system.

7-Mode Snap System

C3 provides a complete seven-mode snap system — the most comprehensive of any independent 2D CAD application. Each mode is activated by a single key press:

Complete Documentation

Built-In User Guide — 60+ Topics

Every feature is documented with step-by-step workflows, keyboard shortcuts, and practical tips. Press ? anywhere in the program to open the guide instantly.

🌐

Export as HTML

Save the entire guide as a standalone HTML page and open it in your favorite browser. Keep it on a second monitor or a tablet while you work — completely independent of the CAD program.

🖨

Print or Save as PDF

Print the complete manual with page numbers and a wide left margin for binder clips. Or save it as a PDF to browse, annotate, or share with your team.

🔍

Smart Search

Type any word or phrase and every match is highlighted in yellow with a match counter. Use Return/Shift+Return to jump between results. Proximity search finds related terms even when you don’t know the exact wording.

⌨

Quick Keys Reference

One click opens the complete keyboard shortcut reference — every hotkey, snap mode, and modifier laid out in a clean 5-column grid. Also accessible with Shift+? from anywhere.

🗪

Clickable Table of Contents

60+ topics organized alphabetically with clickable links. Jump to any section instantly — from Arc Options to Zoom Controls. Back-to-top links throughout for easy navigation.

🎧

Voice-Guided Workflows

Every tool has optional spoken step-by-step prompts. “Click first point… Click second point… Line created.” Learn new features without reading — just listen and draw.

Industry First

Custom Feature Development

Need a specialized function for your workflow? C3 is the only CAD program in the world that offers custom feature development as a service.

⚡

Days, Not Months

Traditional CAD vendors take 6–18 months to respond to feature requests — if they respond at all. C3 features are designed, built, tested, and deployed in days.

🎯

Built for Your Workflow

Describe the function you need. We build it specifically for your use case — not a generic feature that tries to satisfy everyone and satisfies no one.

💡

Real-World Proven

A professional electronics designer requested a PCB workflow feature. It was designed, implemented, tested, and deployed the same day. That’s how C3 development works.

No other CAD company on Earth offers this service. Not Autodesk. Not Dassault. Not Siemens.
Just C3.

John Hardy with the Jensen Twin-Servo microphone preamplifier
MPC-1 microphone preamplifier schematic drawn in CADD300 Modern, showing full circuit with BIAS and SERVO sections, switch LEDs, power supply, and John Hardy Company title block

MPC-1 Preamplifier Schematic — drawn in C3

C3 Layout/Paperspace showing six viewports of the MPC-1 schematic at different scales on a single 11x8.5 inch sheet, with the Files menu showing Auto-Save enabled and Layout 1 tab active

Layout / Paperspace — Six Viewports, One Sheet

The same MPC-1 schematic shown through six independent viewports, each at a different scale and showing a different section of the circuit. Create as many layouts as your project requires, each with unlimited viewports. Assign per-viewport layer groups to show only the layers you need. Title blocks, borders, and annotations live on the paper — not in your model. Everything is stored in a single .cadd file alongside your drawing.

The 43-Year User

“I have been using his program ever since, and I won’t leave home without it.”

I began making mechanical drawings in the later 1960s, with paper and pencil, a ruler and a triangle, and an eraser. I made circuit board designs, drawing them on poster board. In 1977 I made the major upgrade to a light table and drafting arm, with a “precision grid” and lots of Mylar film for circuit board drawings.

Around 1981, my old friend John Christy began writing a CADD program, first on the Hewlett Packard HP85 computer, then upgrading to the HP “200 Series” and then the “300 Series” engineering computers. I bought an HP “216” computer, then an HP “340” computer, and began using Christy’s CADD program. I have been using his program ever since, and I won’t leave home without it.

I have relied on it for drawings of sheet metal parts, injection molded plastic parts, machined parts, schematics, circuit board designs and any odd drawing that I need to make. It has always been very easy to use, with lots of common sense features that were missing in the most expensive CAD programs of the 1990s and 2000s, and probably today.

Christy has always been very responsive to suggestions from his customers, including me. I was fortunate that he gave me a copy of the source code, so I added several simple convenience features. There were two features in particular that seem crazy by modern standards, but in the 1980s they were non-existent or very specialized. The first feature was “Wide Lines”. In the 1980s, if you wanted a wider line in your hard-copy, you put a plotter-pen with a wider tip in your plotter. But for circuit boards, I needed more flexibility and precision, so I added the “Wide Line” feature so that I could do pen plots with much greater precision. In 2012 I needed to add “Gerber File” capability to the program because of a complex circuit board design that I was working on. It was a bare-bones software addition, using the RS232 output of the HP computer to transfer the files to a modern PC.

Now it is 2026, and Christy has accomplished the huge task of bringing this 45-year-old program into the modern world to run on Mac computers. There are tons of new features that rival and surpass the “top” CAD programs of today. I am thrilled to be using it.

— John Hardy, The John Hardy Company, Evanston, Illinois

Eagle CAD ends June 7, 2026. C3 imports your Eagle .BRD files and exports production-ready Gerber. — Migrate before the deadline →

For PCB Designers

Eagle Dies June 7, 2026.
Your Boards Don't Have To.

Autodesk is ending Eagle CAD support on June 7, 2026. C3 imports Eagle .BRD board files and exports industry-standard Gerber RS-274X — giving you a complete fabrication pipeline that doesn't depend on Autodesk's subscription timeline.

Eagle .BRD → C3 Review & Edit → Gerber RS-274X → Fab House
  • ✓  Import Eagle v6+ XML board files — components, traces, pads, vias, silkscreen
  • ✓  Full layer mapping: 16 standard Gerber layers + 4 user-defined
  • ✓  Excellon drill file auto-generated
  • ✓  Board setup: 1–8 copper layers, inches or millimeters
  • ✓  Export in under 10 seconds, even for complex boards
Production-Validated Gerber Output
UCAMCO-verified RS-274X format. Tested against 43 years of production PCB files from The John Hardy Company. Independent verification with GerbV. Zero-error tolerance for fabrication.
Eagle End-of-Life: June 7, 2026. Export your boards now. C3 preserves access to your Eagle designs and gives you a direct path to fabrication.
SparkFun RedBoard PCB imported from Eagle into CADD300 Modern, showing copper traces, component pads, silkscreen text, and multi-layer transparency view
CADD300 Modern Gerber RS-274X Export dialog showing Board Setup with copper layers, units, and default trace width, plus Layer Mapping table with 10 Gerber layer types, C3 layer numbers, and file extensions

How We Compare

C3 vs. The Subscription CAD Industry

Professional capability without the annual tax. Two comparisons follow — first against the volume drafting tier, then against the professional engineering tier.

Volume Drafting Tier

Common 2D drafting products. Subscription-only on PC platforms.

C3 AutoCAD AutoCAD LT DraftSight
Annual Cost One-time purchase $2,030/yr $515/yr $299–$599/yr
3-Year Cost $0 after purchase $6,085 $1,545 $897–$1,797
Native macOS ✓ SwiftUI + CoreGraphics Port Port Port
Offline-First ✓ Zero cloud dependency Optional cloud Optional cloud ✓
DXF Import/Export ✓ R12–R2018+ ✓ ✓ ✓
Eagle .BRD Import ✓ × × ×
Gerber Export ✓ RS-274X + Excellon × × ×
SVG/HTML Export ✓ × × ×
Embedded Images ✓ In-file External refs External refs External refs
Voice Guidance ✓ On/off toggle × × ×
Cross-Window Drag ✓ Option+click Copy/Paste Copy/Paste Copy/Paste
3D from 2D Views ✓ × × ×
Auto Hatch ✓ One-click Boundary pick Boundary pick Boundary pick
Layout / Paperspace ✓ Multi-viewport, layer groups ✓ ✓ ✓
Snap Modes ✓ 7 modes (incl. Tangent, Perp, Nearest) ✓ ✓ ✓
Auto-Save ✓ With crash recovery ✓ ✓ ✓
Custom Features on Request ✓ Days, not months × × ×
Load Drawings as Groups ✓ .cadd files as reusable groups × × ×
Training Required Minimal (sidebar menus + voice guidance) Extensive (steep curve) Extensive Moderate
Support Direct from the developer Enterprise ticket system Enterprise ticket system Ticket system

Professional Engineering Tier

Tools that compete on capability, not price. Annual costs reflect typical commercial seats.

C3 MicroStation SolidWorks Drawings BricsCAD Pro
License Model Perpetual, one-time Subscription Subscription + maintenance Perpetual or subscription
Annual Cost (typical seat) $0 after purchase $3,000–$5,000/yr $4,195 + $1,500/yr maint. $1,020/yr (sub) or $1,890 perpetual
5-Year Cost $12,995 (one-time) $15,000–$25,000 $11,695+ $5,100–$9,390
Native macOS ✓ SwiftUI + CoreGraphics × Windows-only × Windows-only ✓
Apple Silicon Native ✓ arm64 × × Rosetta or x86
Offline-First ✓ Zero cloud dependency Bentley CONNECT cloud 3DEXPERIENCE cloud ✓
License Activation No phone-home, no servers Bentley SELECT server License server / cloud Online activation
File Format .cadd (open JSON) .dgn (proprietary) .slddrw (proprietary) .dwg (industry std.)
DXF Import/Export ✓ R12–R2018+ ✓ ✓ ✓
DWG Import/Export ✓ via ODA File Converter ✓ ✓ ✓ (native)
Eagle .BRD Import ✓ × × ×
Gerber RS-274X Export ✓ UCAMCO-validated × × ×
Voice Guidance ✓ On/off toggle × × ×
Cross-Window Drag ✓ Option+click Copy/Paste Copy/Paste Copy/Paste
Embedded Spreadsheets ✓ 34-function formula engine Linked Excel Linked Excel Linked Excel
Custom Features on Request ✓ Days, not months Bentley consulting VAR / partner channel LISP / API ecosystem
Direct Developer Support ✓ Email the developer Tiered enterprise support VAR / Dassault portal Reseller channel
Heritage / Lineage CADD/200-300 (1982–present) Bentley (1984–) Dassault (1995–) Bricsys (2002–)

Pricing reflects typical commercial seat costs from publicly available sources as of 2026 and varies by region, contract, and reseller. C3 is sold direct.

The Origin Story

Inspired by R. Buckminster Fuller

In 1971, John M. Christy arrived at Carbondale, Illinois, home of Southern Illinois University. There he encountered R. Buckminster Fuller — the legendary architect, inventor, and systems thinker who spent his final academic years at SIU.

"You can do anything you want to do. All you have to do is learn how to learn."
— R. Buckminster Fuller
Fuller described successive approximation as the fundamental process by which nature — and human ingenuity — arrives at optimal solutions. You don't leap to perfection. You iterate toward it. The geodesic dome wasn't born fully formed. It was converged upon — methodically, relentlessly, over time.

Working with geodesic structures, tensegrity models, and synergetic geometry, Christy developed an intuitive feel for spatial relationships that no textbook could provide.

In 1975, CAD systems cost $500,000 and filled entire rooms. Christy was a musician and electronics hobbyist who could barely afford the HP equipment he wanted to use. Fuller's advice was direct: learn how to learn.

So Christy taught himself HP BASIC, then Pascal. By 1982, he had built a CAD system on a $3,000 HP desktop that rivaled systems developed by teams of PhDs. Four years later, Hughes Aircraft was using it to design microwave components for satellites. The result was CADD/200-300, published by Tensegrity, Inc. in Chicago.

The same principle drove the 2025 rebuild: learn the tools (AI-assisted development), apply four decades of domain knowledge, ship in four months.

R. Buckminster Fuller in the classroom at Southern Illinois University
1971–1980 Christy studies with Buckminster Fuller at SIU Carbondale. Geodesic domes, tensegrity, synergetics.
1982 First CADD software written for Hewlett-Packard workstations. Published by Tensegrity, Inc., Chicago.
1983 John Hardy adopts CADD for audio engineering at The John Hardy Company, Evanston, IL. Hardy runs it continuously for the next three decades.
1986 Hughes Aircraft validates CADD for satellite microwave design at their Space & Communications Group.
Oct 2025 C3 development begins: native macOS rebuild using SwiftUI, CoreGraphics, and AI-assisted engineering with Claude.
Feb 2026 Feature-complete with DXF interop, Gerber export, Eagle import, SVG export, multi-window, 3D wireframe, and 20-level undo.

Proven in the Field

Trusted by Engineers Who Build Satellites

"Thank you for the update software. The software is great."
Bart R. Cruz Technical Supervisor, Microwave Laboratory
Hughes Aircraft Company — Space & Communications Group
August 27, 1986
Original 1986 letter from Hughes Aircraft Space & Communications Group endorsing CADD software
43
Years of continuous development
1
User who never stopped (John Hardy, since 1983)
4
Months to rebuild with AI (Oct 2025 – Feb 2026)

From the Original Users

Here’s What CADD/200-300 Users Had to Say

Customer survey responses collected by Tensegrity, Inc., Chicago, IL.

Company Application User Comment
Arizona Public Ser Mechanical & Electrical “Very user friendly; Good package & value; Better than others.”
Bell Comm Research Mechanical & Electrical “Easy to learn; Fast; Easy to go to files and make changes.”
Design Sys/Service Boat & Yacht Designer “Impressed by splines & other useful features; Easy to use.”
Ft Collins Water Plant Blueprints, Electrical “Great support; Faster than PC systems; Great improvements last year.”
Hughes Aircraft Mechanical & Electrical “Very fast; Likes a lot; Bargain; Support excellent; Has 4 copies.”
Ill Switchboard Switching Schematics “Greatest thing since canned beer; Blew other systems tested away.”
Ly-Line Products Lab Furniture/Cabinets “Great! Continually adding upgrades; Liked better than other systems.”
The John Hardy Co PC Board Layout & Mech “Like very much; Very fast; User friendly; Always new features.”
ZYW Corporation Mechanical “Very happy with it; Very fast; Best one tried thus far.”

What This Means for You

Report a Bug Monday.
Ship the Fix Tuesday.

When John Hardy reports a bug or requests a feature, the fix often ships the same day. That isn’t a marketing claim — it’s how the application has been developed for the past six months, and it’s exactly what every C3 user gets. No ticket queue. No roadmap voting. No six-month product manager cycle.

The speed is only possible because the work is grounded in 43 years of CAD engineering judgment. Four decades of knowing exactly what a correct arc tangent looks like, what a Gerber file needs to pass UCAMCO validation, how a professional drafter actually wants a snap system to behave. Combined with Claude as an AI pair-programmer, that judgment compiles into working Swift code at a pace no traditional CAD vendor can match.

Autodesk has thousands of engineers and still takes 6–18 months to act on feature requests. C3 has one engineer, one AI, and forty-three years of context. For anything you need, that turns out to be more than enough.

Under the hood: SwiftUI for the interface, CoreGraphics for pixel-perfect rendering, a QuadTree spatial index for O(log n) performance, analytical geometry throughout. Over 120,000 lines of Swift — the application itself has zero external runtime dependencies and zero licensing servers. (DWG import is the one optional integration: a free, separately installed ODA File Converter handles the DWG↔DXF bridge. C3 runs without it.) Built in four months. Improved every week since.

Days
Typical turnaround on a user bug report or feature request
43
Years of accumulated CAD engineering judgment behind every decision
120,000+
Lines of Swift — zero runtime dependencies, zero cloud services (optional ODA bridge for DWG only)
0
Subscription fees. Ever.

The Philosophy

43 Years of Successive Approximation

Fuller described successive approximation as the fundamental process by which nature — and human ingenuity — arrives at optimal solutions. You don't leap to perfection. You iterate toward it. Each cycle of design, testing, and refinement eliminates error and reveals a closer approximation of the ideal.

That principle became the guiding logic behind everything that is now C3.

Early 1980s
CADD/85
First approximation. Established the core problem space and intellectual foundation on HP workstations.
→
1986–87
CADD/86–87
Refined the model. Tightened methodology, expanded capability. The errors of the first pass became the lessons of the second.
→
1983–1995
CADD/200–300
Generational leap. Proven at Hughes Aircraft, adopted by Hardy. A mature system that understood its own history well enough to transcend it.
→
2025–Present
C3
The current approximation. Four decades of wisdom, rebuilt with AI at the speed the methodology always deserved.

The approximation continues.

From the Archives

The Original CADD/200-300 Data Pack (1986)

The original software ran on Hewlett-Packard workstations (HP 216, 217, 310, 320) and cost $4,000 for the first workstation license. It supported HP plotters up to E-size (34"×44"), digitizing tablets for input, and featured the same grid zero + snap increment precision system that C3 uses today.

The 1986 data pack includes sample drawings from Hughes Aircraft (satellite microwave assemblies), The John Hardy Company (audio electronics), Ly-Line Products (furniture specifications), and Pfauter (industrial machinery) — showing the range of industries that trusted this software from the beginning.

Published by Tensegrity, Inc. at 2424 Addison Street, Chicago, IL 60618.

CADD/200 Computer-Aided Design & Drafting brochure — HP workstation with plotter and digitizing tablet, Tensegrity Inc.

Sample Pages from the 24-Page Data Pack

Scroll to browse →

Dimensioning examples — bolt circle with radius, diameter, and angular dimensions

Dimensioning Examples

MT-101A Fin Detail — John Hardy Co injection mold part, drawing scale 10:1

Hardy Co — Mold Detail

PCB component layout — dense board with ICs, capacitors, resistors, connectors

PCB Component Layout

MPC-3000 PCB artwork — copper trace routing for John Hardy preamp board

MPC-3000 PCB Traces

MPC-3000 schematic — BIAS and SERVO circuit sections, John Hardy Co

MPC-3000 Schematic

Ly-Line Products counter height storage catalog page, 1985

Ly-Line — Catalog Page

Pfauter lubrication schematic — recirculating and progressive centralized systems

Pfauter — Lubrication

Ly-Line Flex II System full assembly drawing with bill of materials and title block

Ly-Line — Assembly Drawing

CADD/200-300 business card design — the software drew its own marketing material

Magazine Ad Insert

CADD/200-300 Direct Execute Keys reference — same keyboard-driven workflow used in C3 today

Direct Execute Keys (1986)

Pricing

Own It Forever. No Subscriptions.

One purchase. Perpetual license. Free updates. Your software, on your machine, working offline — forever.

Perpetual license. No subscription. No cloud lock-in.
You own the software. You own your files. You decide when to upgrade.
Professional License
$12,995
One-time purchase — own it forever
  • Full application, every feature included
  • Perpetual license — no expiration, no renewal
  • Free updates for the first year
  • Direct support from the developer
  • Runs offline — no cloud, no internet required
  • Your software, your machine, your data
Request Private Access & Schedule a Demo

Volume & Site Licenses

Multi-seat departments, engineering groups, and site-wide deployments are accommodated with volume pricing, purchase orders, and NET-30 terms. Contact us for a tailored quote.

The Math Speaks for Itself

AutoCAD costs $2,030/year. In 5 years, that’s $10,150 — and you own nothing. Cancel the subscription, lose the software.

C3: One payment of $12,995. You own a perpetual license. It works forever. No renewals, no recurring charges, no cloud dependency. After 6.5 years, every day you use it is free.

Year 7 and beyond: AutoCAD = $14,210+ and counting. C3 = $12,995. Done.

Common Questions

FAQ

What if Tetra720 goes out of business?
C3 is a self-contained application with no runtime dependencies. No licensing servers, no dongles, no cloud validation. Your software keeps working forever, even if we shut down tomorrow. (DWG import optionally uses the free ODA File Converter as an external bridge; C3 itself runs without it, and every other format — DXF, Eagle, Gerber, SVG, PDF, .cadd — is handled natively.)
What happens to my drawings if I stop using C3?
Your drawings are yours. C3’s native .cadd format is plain JSON — human-readable, inspectable with any text editor, and trivially parsed by any programming language. You can also export every drawing to DXF (R12, round-trip tested with AutoCAD, DraftSight, and LibreCAD), SVG, PDF, or Gerber RS-274X. No DRM. No encrypted container. No proprietary blob. If you ever move to another CAD program, your work moves with you.
Can I try before buying?
Contact us for a personalized demo. We'll walk through your specific workflow and show you exactly how C3 handles your use case.
What file formats does C3 support?
Import: DXF (R12–R2018+), Eagle .BRD (v6+), CADD95 (.C95), PNG/JPEG images. Export: DXF R12, Gerber RS-274X, Excellon drill, SVG/HTML, PDF. Native format: .cadd (JSON).
Does C3 run on Windows?
No. C3 is native macOS only (Apple Silicon and Intel). This isn't a port — it's designed specifically for Mac using SwiftUI and CoreGraphics.
Will there be a subscription option?
No. Ever. We believe professional tools should be owned, not rented.
Can I trust C3's Gerber output for production boards?
Every Gerber file passes UCAMCO validation. We've verified against Hardy's production boards that have been successfully manufactured for decades. Zero tolerance for errors.

Runs on Any Mac — macOS 15 or Later — No Dependencies.

Self-contained application. No external services required.

macOS Native

Apple Silicon & Intel

⚠️

No Internet

Works completely offline

🔒

No Telemetry

Your data stays yours

⚡

Fast Startup

Lightweight, focused app