Languages
C
Close-to-the-metal systems and firmware, built by engineers who run what they ship.
Overview
C is the foundational systems programming language, and almost everything you use runs on top of it. Operating system kernels, device drivers, embedded firmware, network stacks, database engines, the runtimes behind higher-level languages, and the performance-critical libraries those languages call into — a large share of them are written in C. It is a small, deliberately simple language that maps closely onto how a machine actually works: you get direct control over memory and hardware, a minimal runtime that adds almost nothing between your code and the processor, and a portability that has carried C onto everything from an eight-bit microcontroller to a supercomputer. When people say a language is “close to the metal”, C is the language they are measuring against.
That closeness is the whole point and the whole danger. C hands you raw pointers and manual memory management — you call malloc to allocate and free to release, and the compiler does nothing to stop you getting it wrong. There is no garbage collector, no bounds checking, no built-in strings or collections or generics, and no safety net. The upside is control and predictability: no hidden allocations, no runtime pauses, a tiny footprint, and behaviour you can reason about instruction by instruction. The downside is that the same freedom is why buffer overflows, use-after-free and the majority of historical security vulnerabilities trace back to C and its close relative C++. The language will let you do exactly what you said, including corrupt your own memory.
We work in C where it genuinely earns its place: embedded and firmware work on constrained hardware, performance-critical native components that a higher-level system calls into, and maintaining or modernising the large bodies of legacy C that quietly run real businesses. We are also blunt about the alternative. For new systems work where memory safety matters, Rust now gives you C-class performance with an entire category of those vulnerabilities ruled out at compile time, and it is frequently the better choice. We will tell you when that is the case rather than write you new C you did not need.
Best for — Embedded firmware, performance-critical native components, and the maintenance and modernisation of legacy C — work on constrained hardware or inside existing C ecosystems where direct control and a minimal runtime are the deciding factors.
Why teams choose C
Direct control over memory and hardware
C lets you read and write memory-mapped registers, place data at specific addresses, and manage allocation by hand, with no runtime deciding things behind your back. On embedded and driver work this is not a nicety but a requirement — you are talking to hardware directly, and C is the language built to do it.
A minimal runtime and tiny footprint
A C program carries almost no runtime with it — no garbage collector, no virtual machine, no heavy standard library you must ship. That is what lets the same language run on a microcontroller with a few kilobytes of RAM and inside a high-performance server, and why C binaries start instantly and behave predictably.
Portability and the universal ABI
C compiles to almost every architecture that exists, and the C ABI is the lingua franca that other languages interoperate through. When Python, Rust, Go or anything else needs to call native code, it speaks C at the boundary — so a well-built C library has a reach far beyond C programs alone.
Why businesses choose C
- You are building for constrained or embedded hardware, or working inside an existing C ecosystem, where the toolchain, footprint and direct hardware access leave C as the natural — often the only — choice.
- You need a small, fast native component with a minimal runtime and predictable behaviour, and you value control over the convenience a higher-level language would give you.
- You have legacy C that runs something important and needs maintaining, hardening or modernising by people who understand both the language and the risks it carries.
- You want senior judgement on whether C is even the right call — including being told plainly when Rust would give you the same performance without the memory-safety risk, and cost you less over the life of the system.
What we build with C
The capabilities this technology is genuinely strong at — and what we most often build with it.
Pointers and manual memory management
Pointers and the malloc/free model are the core of C and the source of both its power and its danger. We treat ownership deliberately — who allocates, who frees, and when — because unclear ownership is where leaks, double-frees and use-after-free bugs breed. Disciplined allocation patterns and clear lifetime rules are the difference between C that is safe to run for years and C that fails in the field.
Direct hardware and register access
On embedded and driver work, C reads and writes memory-mapped hardware registers, handles interrupts, and places data at fixed addresses. We use volatile correctly, respect the memory model, and treat the hardware datasheet as the specification — the details other languages abstract away are exactly the details that matter here.
The preprocessor and portable builds
C’s preprocessor handles conditional compilation, feature flags and platform differences, and the build — make, CMake, or a vendor toolchain — ties it to a target. We keep macro use disciplined rather than clever, because an over-used preprocessor is where portable C turns into unreadable C, and we structure builds so the same source cross-compiles cleanly to different hardware.
The C ABI and foreign-function boundaries
The C ABI is how nearly every other language calls native code, so a well-designed C interface is a component many systems can share. We design these boundaries carefully — clear ownership across the boundary, stable struct layouts, explicit error contracts — because a leaky or ambiguous C interface becomes a liability for every language that depends on it.
Sanitisers and static analysis in the loop
Because the compiler gives you no memory safety, tooling has to. We build with AddressSanitizer and UndefinedBehaviorSanitizer, run static analysers such as clang-tidy and Coverity-class tools, and treat their findings as build failures rather than suggestions. In C, this discipline is not optional polish — it is how you catch the class of bug the language refuses to catch for you.
Deterministic, allocation-aware performance
C’s value is predictable behaviour, so we write hot paths that avoid needless allocation, respect cache behaviour, and do not surprise you at runtime. On real-time and embedded targets we favour static or pool allocation over ad-hoc malloc, because a predictable memory pattern is often more important than raw speed.
Use cases
Embedded firmware and microcontrollers
Firmware for microcontrollers and constrained devices, where a few kilobytes of RAM, direct register access and real-time constraints make C the default. This is the work C was built for and where it still has no serious general-purpose rival on the smallest targets.
Device drivers and OS-level code
Drivers, kernel modules and low-level system components that must speak to hardware directly and match an operating system written in C. Here the surrounding ecosystem, the ABI and the toolchain are all C, and matching them is the pragmatic choice.
Performance-critical native components
Small, fast libraries and hot paths — codecs, parsers, numerical kernels — that higher-level systems call into through the C ABI, where a minimal runtime and predictable, allocation-free behaviour are the whole point of dropping down to C.
Maintaining and modernising legacy C
Large, long-lived C codebases that quietly run real businesses and need maintaining, hardening or carefully modernising — adding tests and sanitisers, closing memory-safety holes, and deciding what is worth rewriting in a safer language and what is best left stable.
When C is the right choice
- You are targeting constrained or embedded hardware — microcontrollers, firmware, real-time systems — where the toolchain, the footprint, and the direct hardware access make C the default and often the only practical option. This is C’s home ground and nothing displaces it easily.
- You are working inside an existing C ecosystem: an OS kernel, a driver, a database engine, or a mature codebase where the surrounding code, ABI and build system are all C. Matching the ecosystem you must live in usually beats introducing a second language at the boundary.
- You need a tiny, fast native component — a hot path, a codec, a library other languages will call through the C ABI — where a minimal runtime and predictable, allocation-free behaviour are the point.
- Wrong for: a new system where memory safety matters and you are free to choose. Rust gives you the same performance and rules out use-after-free and buffer overflows at compile time. Choosing C here is taking on a well-documented class of security risk for no benefit you cannot get elsewhere — we will say so plainly.
- Wrong for: ordinary application, web or business logic. C has no strings, no collections, no generics and no memory safety, so development is slow and error-prone compared with almost any higher-level language. Reaching for C to build a normal application is a category error that will cost you months and ship you bugs.
C: pros and cons
Strengths
- Unmatched control and predictability — direct memory and hardware access, no hidden allocations, and behaviour you can reason about down to the instruction, which is exactly what embedded and systems work demands.
- A minimal runtime and tiny footprint let the same language run on the smallest microcontrollers and the largest servers, starting instantly with no garbage collector or virtual machine overhead.
- Extreme portability and a mature, stable toolchain — C compiles to virtually every architecture in existence, and decades of compilers, debuggers and analysis tools are battle-tested.
- The C ABI is the universal interoperability layer, so C code is callable from nearly every other language, giving a well-built C library reach far beyond C itself.
Trade-offs
- Manual memory management makes C dangerous. You allocate and free by hand with no safety net, and the buffer overflows, use-after-free and double-free bugs this produces are behind the majority of historical security vulnerabilities. This is the defining trade-off, not a footnote.
- There is no memory safety and no bounds checking. The compiler will happily let you read past an array, dereference a freed or null pointer, or corrupt the stack — and the failure often shows up far from its cause, making these bugs expensive to find.
- No modern conveniences. C has no built-in strings, collections, generics, exceptions or namespaces, so a great deal of routine work is manual and repetitive, and much of what other languages give you free you must build or import and maintain yourself.
- Development is slow and error-prone compared with higher-level languages. The same low-level control that makes C powerful for systems work makes it a poor fit for ordinary application logic, where you would spend your time managing memory instead of solving the problem.
Architecture
The load-bearing architectural decision in a C project is memory ownership: for every allocation, who owns it, who is responsible for freeing it, and how long it lives. C gives you no help enforcing this, so we make it explicit in the design rather than leaving it to convention — clear allocation and free pairings, ownership documented at every interface boundary, and a bias towards static or pool allocation on constrained targets where ad-hoc malloc is a liability. Ownership discipline is what separates C that runs cleanly for years from C that leaks and corrupts in the field.
Around that, we keep modules small with narrow, well-documented interfaces, isolate platform-specific and hardware-specific code behind clean boundaries so the bulk of the codebase stays portable, and keep preprocessor use disciplined so the source remains readable. On mixed-language systems we treat the C ABI boundary as a first-class part of the architecture, defining ownership and error contracts explicitly, because an ambiguous native interface becomes every caller’s problem.
Performance
C sets the performance benchmark other languages are measured against. It compiles straight to native machine code with no interpreter, no virtual machine and no garbage collector, so there is nothing between your logic and the processor and no runtime pauses to tune away. On the hot paths and constrained hardware where C is the right tool, this is precisely why it was chosen — predictable, allocation-aware behaviour that you can reason about instruction by instruction.
Reaching that ceiling is still engineering, not a given. We profile before optimising rather than guessing, pay attention to cache behaviour and memory layout, avoid needless allocation in hot paths, and lean on compiler optimisation and the sanitisers together so that fast code stays correct. The honest caveat is that C’s performance comes hand in hand with its danger: the same manual control that makes it fast is what makes a memory bug possible, so performance work and safety discipline are never separate activities in C.
Security
C is where a large share of the serious security vulnerabilities in software history come from, and the reason is structural: manual memory management with no bounds checking means buffer overflows, use-after-free, double-free and integer overflows are all a slip away, and each is exploitable. The language will not catch these for you, so in C, security is a discipline you impose rather than a property you inherit. We treat it that way from the first line.
In practice that means memory-safety discipline built into the process, not bolted on. We compile and test with AddressSanitizer and UndefinedBehaviorSanitizer, run static analysis and treat its findings as failures, bounds-check every buffer and validate every input, use safer standard-library functions and our own checked wrappers rather than the notorious unsafe ones, and fuzz the parsers and boundaries that untrusted data reaches. Where memory safety is genuinely critical and the work is new, we will also make the honest case for Rust, which removes this entire class of vulnerability at compile time rather than asking you to catch it by hand for the life of the system.
Scalability
C scales downwards and outwards in ways higher-level languages cannot. Downwards, its tiny footprint and minimal runtime let the same well-written component run on hardware measured in kilobytes, so scaling to more, smaller or cheaper devices is a matter the language never gets in the way of. Per machine, C uses memory and CPU efficiently enough that a C component often does far more work per core and per byte than a managed-language equivalent, which is frequently the reason it sits on the hot path in the first place.
The harder scaling problem in C is the codebase and the team, not the load. Without memory safety or modern module conveniences, a large C project stays maintainable only through discipline — narrow interfaces, clear ownership, thorough tests, and sanitisers and static analysis in continuous integration so that regressions surface at build time rather than in production. We build that scaffolding in from the start, because it is what lets more people work safely in a C codebase, and it is exactly what tends to be missing from the legacy C we are asked to rescue.
C integrations & ecosystem
The technologies we most often pair with it — each links to how we work with it.
How we work
We start by pressure-testing whether C is the right choice at all. For embedded, driver, OS-level or existing-ecosystem work it often is, and we will say so; for new systems where memory safety matters, we will make the honest case for Rust instead, because writing you new C that carries an avoidable class of security risk is a mistake we would rather you did not pay for. When C does fit, we settle memory ownership, module boundaries and the build and toolchain early, since these are the decisions the language will hold you to for the life of the codebase.
From there we build in thin, testable slices with the safety tooling switched on from day one — sanitisers, static analysis and tests as part of the build rather than an afterthought — because in C, correctness that is not checked is correctness you do not have. The engineers who design the system are the ones who write it and keep it running; that is what operating what we build means. It shows up as disciplined ownership, minimal clever preprocessor tricks, and a codebase your own team can pick up and maintain long after we have gone.
The service behind it
Delivered throughCustom Software DevelopmentWhat we build with C
The disciplines this technology most often shows up in — from a first build to taking over and stabilising an existing one.
How we deliver
- 01
Discover
We map the system, the constraints and the business it serves — including the parts nobody documented.
Architecture brief
- 02
Architect
Decisions get made, written down and defended before a line of production code exists.
Decision records
- 03
Build
Short cycles against working software. You see progress in the product, not in a status deck.
Shipping increments
- 04
Operate
Monitoring, incident response and iteration. The system is alive, so the engagement is too.
Runbooks & SLOs
Industries we use C in
Domain knowledge changes what gets built. A few of the sectors we know before the first meeting.
Also in Languages
Why teams choose us for C
Senior engineers only
C punishes inexperience directly and dangerously — the gap between disciplined ownership and a use-after-free is judgement earned on previous systems. The people making your memory and hardware decisions have made them before and lived with the consequences. There are no juniors learning pointers on your firmware.
We operate what we build
We run the systems we ship, so we optimise for years of safe operation on real hardware, not a demo. That means sanitisers and static analysis in the build, disciplined memory ownership, and a codebase your own team can maintain — the things that keep a C system from failing quietly in the field.
Honest about C and Rust
If your work is new and memory safety matters, we will make the case for Rust before you commit to new C, because it removes an entire class of vulnerability the C compiler will never catch. We would rather turn down C work than write you something that carries an avoidable risk.
Typical timeline
- 01
Discovery and ownership design
One to two weeks confirming C is the right call, then settling memory ownership, module boundaries, the target hardware and the build and toolchain before code volume grows.
- 02
First working slice
Two to three weeks delivering one real capability end to end on the actual target, with sanitisers, static analysis and tests already in the loop, to prove the design against real hardware rather than a plan.
- 03
Iterative build
Feature-by-feature delivery in short cycles, each tested and analysed, with memory-safety checks and profiling handled as we go rather than deferred to the end.
- 04
Hardening and handover
A full memory-safety and static-analysis pass, fuzzing of the boundaries untrusted data reaches, profiling on the hot paths, and documentation so your team can own and extend the code safely.
How pricing works
- Fixed-scope builds for well-defined C work — a firmware module, a driver, a native library, a specific performance-critical component — quoted once we understand the hardware and the constraints.
- Monthly senior engagement for ongoing embedded or systems work where scope evolves and you want continuity from the people who know the hardware and the codebase.
- Focused audits and rescues for existing C — a memory-safety review, a hardening pass with sanitisers and static analysis, or a considered plan for modernising or partially rewriting a legacy codebase — priced by assessment.
Hire C engineers
Need C capacity on your own team? We embed named senior engineers into your existing team — reporting to your leads, working in your rituals — so you add capacity without a hiring cycle.
Hire C engineersCommon questions
Should we still use C for a new project, or Rust?
It depends on the target. For embedded and firmware on very constrained hardware, for driver and OS-level work, or inside an existing C ecosystem, C is often still the natural or only practical choice. For new systems work where you are free to choose and memory safety matters, Rust now gives you the same C-class performance while ruling out buffer overflows and use-after-free at compile time, so it is frequently the better call. We will tell you honestly which side of that line your project sits on rather than default to writing new C.
Why is C considered dangerous, and can that be managed?
Because it has no memory safety. You manage memory by hand with malloc and free, there is no bounds checking, and the compiler will let you overflow a buffer, dereference a freed pointer or corrupt the stack — bugs that are behind the majority of historical security vulnerabilities. It can be managed, but only through discipline: sanitisers and static analysis in the build, rigorous bounds checking, clear memory ownership, and fuzzing at untrusted boundaries. That discipline is exactly how we work in C, but it is a cost you carry for the life of the codebase, which is why we raise Rust for new safety-critical work.
Can C code work with our Python, Go or Rust systems?
Yes — that is one of C’s enduring strengths. The C ABI is the universal interoperability layer, so nearly every language, including Python, Go and Rust, can call C code through it. A well-built C library becomes a fast native component that many higher-level systems can share. The work that matters is designing that boundary carefully: explicit ownership across the interface, stable struct layouts, and clear error contracts, because an ambiguous C interface becomes a problem for every caller that depends on it.
Can you maintain or modernise our existing C codebase?
Yes, and it is a large part of what we do in C. We start with an honest audit — a memory-safety review, sanitisers and static analysis run over the code, and tests added around the parts that matter — so you can see where the real risks are before deciding anything. From there we harden what needs hardening, and give you a considered plan for what is worth rewriting in a safer language and what is best left stable. Not all legacy C should be rewritten; a lot of it should be understood, tested and left to keep running.
Is C fast, and how do you get the most out of it?
C is the benchmark other languages are measured against — it compiles to native machine code with no interpreter, virtual machine or garbage collector between your logic and the processor. But raw speed still takes engineering: we profile before optimising rather than guessing, pay attention to cache behaviour and memory layout, and avoid needless allocation on hot paths, often preferring static or pool allocation on constrained targets. The important caveat is that C’s speed and its danger share the same root, so we never treat performance work and memory-safety discipline as separate jobs.
Building on C?
A technical conversation with the engineers who would do the work. If we are not the right fit, we will say so on the call.