c-programming-language

The C Programming Language (K&R, 2nd Edition)

Apply this skill when writing, reviewing, or debugging C code, or explaining C semantics — grounded in K&R's philosophy that C trusts the programmer completely: no hidden costs, no runtime safety net, and correctness is the programmer's explicit responsibility at every step.

Core concepts

"Trust the programmer" — C deliberately omits bounds checking, garbage collection, and most runtime safety nets, on the premise the programmer knows what they're doing and wants no hidden cost. This means C code that "looks fine" can still be wrong in ways the compiler won't catch — when reviewing C, actively look for what the language won't stop, not just syntax errors.

Pointer/array duality & pointer arithmetic — a[i] is defined as *(a + i); arrays decay to pointers in most expressions, and pointer arithmetic is scaled by the pointee's size automatically. Understanding this equivalence is the key to reading and writing idiomatic C (pointer-walking a buffer instead of indexing, passing arrays as pointer+length). When debugging array/pointer code, mentally rewrite between the two forms to spot off-by-one or scaling errors.

Declarations mirror use (the right-left / "spiral" rule) — A declaration like int *a[10] or int (*a)[10] should be read by working outward from the identifier following C's precedence rules ([] and () bind tighter than *), not left-to-right. When a declaration is confusing (arrays of pointers, pointers to functions, pointers to arrays), decompose it this way rather than guessing — this is the single most common source of "wait, what does this even declare" confusion in C.

Manual memory management & ownership — Every malloc/calloc needs an unambiguous owner responsible for exactly one matching free; there's no garbage collector to fall back on. When reviewing allocation code, explicitly trace: who allocates, who's responsible for freeing, and what happens on every exit path (including error returns) — leaks and double-frees are almost always a broken answer to "who owns this."