What does `dword ptr` mean?

assembly x86 dword pointers
小太郎 picture 小太郎 · Jun 7, 2010 · Viewed 145.4k times · Source

Could someone explain what this means? (Intel Syntax, x86, Windows)

and     dword ptr [ebp-4], 0

Answer

unwind picture unwind · Jun 7, 2010

The dword ptr part is called a size directive. This page explains them, but it wasn't possible to direct-link to the correct section.

Basically, it means "the size of the target operand is 32 bits", so this will bitwise-AND the 32-bit value at the address computed by taking the contents of the ebp register and subtracting four with 0.

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