Solidity stores its allocation pointer at memory address 0x40.
LET’S PICTURE IT
A bookmark identifies where the next managed workspace allocation should begin.
SEE IT FOR YOURSELF
Use temporary memory in one execution frameStep 1 / 4
This frame uses temporary byte-addressed memory. Solidity normally keeps a free memory pointer at address 0x40, initially pointing to 0x80.
This frame uses temporary byte-addressed memory. Solidity normally keeps a free memory pointer at address 0x40, initially pointing to 0x80.In this simplified example, MSTORE writes integer forty-two into thirty-two bytes beginning at memory byte 0x80. Accessing this range may expand active memory.MLOAD at byte 0x80 reads that complete thirty-two-byte word back as a stack value. It does not fetch persistent storage or network data.RETURN can expose a chosen memory range as output. Frame memory is temporary; returning data does not turn it into persistent contract state.
Animated local teaching model. No wallet, RPC or live blockchain data. Some labels and hashes are abbreviated for readability.
Distinguish pointer location and value
The memory word at address 0x40 holds the free memory pointer. The address 0x40 and the pointer value stored there are different numbers.
Recognize the conventional initial value
Solidity normally initializes the pointer to 0x80 after reserved scratch, pointer and zero-slot regions. This is a compiler memory convention, not a universal EVM opcode rule.
Do not assume pointed bytes are zero
Temporary compiler operations can use memory around the pointer without permanently advancing it. The pointer alone is not a promise that the referenced region contains zeros.
Coordinate manual allocation
Assembly that retains newly allocated memory must follow the applicable memory conventions and advance the pointer appropriately. Incorrect bookkeeping can corrupt later compiler-managed values.
Inspect the layout
mload(0x40) // read the pointer value
// Usually 0x80 at initial Solidity setup.
// 0x60–0x7f is the reserved zero slot.
A convention sketch; it is not a complete memory allocator.