ByteCount — number of bytes used to store an expression

LeafCount — number of "leaves" in an expression

Length  ▪  Depth  ▪  BitLength  ▪  Hash

Clear — clear main values of a symbol

ClearAll — clear all values and attributes

$HistoryLength — number of previous outputs to store

$RecursionLimit  ▪  $IterationLimit  ▪  $MaxNumber  ▪  $MaxPrecision

MemoryConstrained — abort a computation if it uses too much memory

MemoryInUse — amount of memory currently in use

MaxMemoryUsed — maximum memory used in this Wolfram Language kernel

MemoryAvailable — estimated amount of additional memory available to this kernel

Share — internally share common subexpressions

FileSize — size of an external file

Compress — generate a compressed string representation of any expression

Uncompress — recover an expression from its compressed string representation

BinarySerialize  ▪  BinaryDeserialize

Short — display a shortened version of an expression

Low-Level Optimizations

Remove  ▪  ClearSystemCache  ▪  SystemOptions  ▪  SetSystemOptions