# SAC The Statically Allocated Collections. These collections have a fixed size. Its size is one of the parameters during macro expansion, producing a C array. ## CMC vs. SAC The `cmc` collections hold their data either with nodes or a buffer that can be reallocated. The `sac` collections only have an array with fixed size and don't perform any allocation on the heap. ```c // A CMC List struct List { T *buffer; /* Other fields */ }; // A SAC List struct List { T buffer[SIZE]; /* Other fields */ }; ```