Glossary

Quick definitions, A to Z. Terms point to the guide that explains them in context.

Address — a variable's location in memory. &x gives it.

Buffer overflow — writing past the end of an array, corrupting whatever sat next to it. A classic C bug.

Compiler — translates C source into machine code. GCC and Clang are the common ones.

Declaration — announcing a function's shape (name, parameters, return type) before use. See Functions.

Dereference — following a pointer to its value: *p.

Double free — freeing the same heap memory twice. Corrupts the allocator.

Garbage collector — automatic memory cleanup, which C does not have. You do it yourself.

Header file — shared declarations in a .h file, pulled in with #include.

Heap — memory you request with malloc and return with free. See Memory Basics.

Linker — combines compiled pieces (and libraries) into the final program. "Undefined reference" is its complaint.

malloc / free — request and return heap memory. Every malloc needs a free.

NULL — a pointer to nothing. Dereferencing it crashes.

Pointer — a variable holding a memory address. See Pointers.

Preprocessor — the pass before compiling that handles #include and #define.

Prototype — another word for a function declaration.

Segfault — crash from touching memory you shouldn't. Short for segmentation fault.

sizeof — operator reporting a type's size in bytes. Never assume sizes.

Stack — automatic memory for local variables. Dies with the function.

Static typing — variable types are fixed when declared, unlike Python.

Undefined behavior — the standard's way of saying "anything can happen, including seeming to work." Avoid, don't exploit.

Warning — the compiler noticing something suspicious. With -Wall, read every one.