Model control logic with blocks, simulate, verify and generate clean C99, with no dynamic allocation and reproducible byte for byte. Built for embedded teams that write everything by hand today.
typedef struct { bool armed; bool alarm; } FlightControl_Controller_Outputs; void FlightControl_Controller_step(FlightControl_Controller_State *self, const FlightControl_Controller_Inputs *in, FlightControl_Controller_Outputs *out); /* no malloc, no globals */
Everything BOLD does today, in a local desktop application. The model is checked on every edit and the generated code is always the same for the same model.
A canvas with block diagram symbols (ANSI/IEEE 91 logic gates, summing circle, gain), editable wire routes and reusable subsystems.
A graphical editor for states and transitions with synchronous automata semantics: strong and weak transitions, actions, forks, restart and resume.
A built-in reference simulator: run step by step or live, and write test scenarios with oracles, row by row.
There is no "verify" button: types, causality, combinational cycles and recursion are checked as you edit, with marks right on the diagram.
Sound interval analysis for integers: points out operations that may overflow, divisors that may be zero and shifts out of range, even through Unit Delay feedback loops.
One .c/.h pair per subsystem, only <stdint.h> and <stdbool.h>, no compiler extensions and no timestamps.
Activate If and Activate When blocks, instances with restart and every, and the map, fold, mapfold and forward iterators.
A .boldproj project plus one .bold file per library. UTF-8 JSON with canonical key order: the same model always saves the same text, and diffs stay readable.
bool, char, int8–int64, uint8–uint64, float32, float64, arrays, structures, enumerations and global constants. Operations never mix types: only Numeric Cast converts.
The core of BOLD is pure TypeScript, separate from the interface. Each stage has a clear responsibility, and the generated C is tested against the simulator.
Project, libraries and subsystem definitions.
.boldproj · .boldStructure, types, causality and numeric ranges.
analysisInstances, execution order and cycles between subsystems.
graphA validated intermediate representation with the step schedule.
irIntermediate C structure and init/step modules.
cast · codegenThe integrating program calls step once per logical step, at the configured period. Nothing more.
<stdint.h> and <stdbool.h>, no compiler extensions./* FlightControl_Filter.h — generated by BOLD */ #include <stdint.h> #include <stdbool.h> /* Confirms a discrete input (true on 3 consecutive steps) and reports its rising edge. */ typedef struct { bool raw; } FlightControl_Filter_Inputs; typedef struct { bool clean; bool rising; } FlightControl_Filter_Outputs; typedef struct { /* one object per instance */ /* memory of the pre blocks ... */ } FlightControl_Filter_State; void FlightControl_Filter_init(FlightControl_Filter_State *self); void FlightControl_Filter_step(FlightControl_Filter_State *self, const FlightControl_Filter_Inputs *in, FlightControl_Filter_Outputs *out);
Each block has its output as a function of inputs and state, types, memory, domain, the generated C and examples run by the tests.
BOLD-E011Combinational cycle: the signal depends on itself in the same stepBOLD-E006Recursive use of a subsystem (A → B → A)BOLD-W012The sum may leave the range of int16BOLD-W013The divisor may be zeroBOLD-W010State never reached from the initial stateBOLD-W008Subsystem is unused and not marked as rootQuick fixRemove redundant cast · mark as rootBOLD's competitor is not just another modeling tool. It is the way most small teams work today.
No block limit, no students-only restriction. Companies that need more pay for infrastructure, support and assurance.
Personal, academic and commercial use, for companies of any size.
For organizations that need control, collaboration and support.
For programs that need verification evidence and qualification.
BOLD Desktop stays free and local. Around it, HARPRON is building:
Shared projects and requirements, model reviews, semantic diff, verification history, traceability and CI/CD.
A modeling assistant, with the option to use your own API key or a local model.
A marketplace of block libraries: communication interfaces, BMS, avionics and community components.
Validation and code generation in your continuous integration pipeline.
AppImage, deb and dmg packages, declared after verification on each system.
A path to use in critical systems, with evidence per standard.
Open the FlightControl example project from File › Open Example Project and generate your first C code in minutes.