C Practice

Master manual memory management, pointer arithmetic, and undefined behavior avoidance.

Language Essentials

Concept	Details
Memory Model	Manual allocation (malloc/free), stack vs heap, no GC
Type System	Weak static typing, implicit conversions, void* generics
Error Handling	Return codes, errno, setjmp/longjmp (avoid)
Concurrency	pthreads, atomics (stdatomic.h), no language-level async
Build	gcc/clang, make, cmake, header/source separation
Standard	C11 (prefer) or C17

Key Idioms

• Opaque pointers for encapsulation (struct Foo; in header, definition in .c)
• Goto cleanup pattern for resource management
• Flexible array members for variable-length structs
• Static inline functions in headers for zero-cost abstractions
• Compound literals for temporary struct values
• Designated initializers for readable struct initialization

Reference Documentation

• C11 Standard Draft (N1570) — free
• cppreference.com/w/c — best online reference
• The C Programming Language (K&R, 2nd ed.) — the classic
• Modern C by Jens Gustedt — free PDF
• Expert C Programming by Peter van der Linden — deep dives

Practising these

practice/bin/ol list  build c          # which of these have references yet
practice/bin/ol start build c 01       # clone it stubbed into .scratchpad/
practice/bin/ol check build c 01       # run it; exit code is the verdict
practice/bin/ol diff  build c 01       # your attempt against the reference

Exercises are ordered by concept, not by difficulty, so pick by the stars rather than by the number. An exercise listed below with no reference yet is a row in this table and nothing more; see the practice path for how the harness works.

Exercises

Implement each using only the C standard library. No external dependencies.

#	Exercise	Concepts	Difficulty
01	Dynamic array (vec.h)	realloc, growth factor, generics via macros; course version: ds.01, lang.03	⭐⭐
02	Hash map (open addressing)	Hash functions, probing, load factor; course version: ds.02 (this drill is its worked baseline)	⭐⭐⭐
03	Linked list (intrusive)	Container-of macro, pointer manipulation; course version: ds.03	⭐⭐
04	Binary heap	Array-based, sift_up/sift_down; course version: ds.04	⭐⭐
05	Merge sort (in-place)	Pointer arithmetic, recursion	⭐⭐
06	Graph (adjacency list)	Flexible arrays, BFS/DFS	⭐⭐⭐
07	Thread pool	pthreads, condition variables, work queue; course version: rt.03	⭐⭐⭐⭐
08	Arena allocator	Memory management, alignment, bump allocation; course version: rt.02	⭐⭐⭐
09	String interning	Hash table, strdup, lifetime management	⭐⭐⭐
10	Simple HTTP parser	State machine, buffer management, recv	⭐⭐⭐⭐