0x40000000

0x40000000 is a hexadecimal constant that represents the decimal value 1,073,741,824, which is 2^30. In hexadecimal notation it appears as 0x40000000, with a single nonzero nibble followed by zeros. This makes it a convenient reference point for both large numeric values and memory addresses in 32-bit systems.

In programming and computing, 0x40000000 is often used as a memory address or as a base constant. In many ARM Cortex-M microcontroller architectures, the region starting at 0x40000000 is reserved for memory-mapped peripheral registers. Peripheral blocks and their control registers are commonly defined with offsets from this base address, making 0x40000000 a conventional starting point for the peripheral address space in various families.

As a bitmask, 0x40000000 corresponds to the 30th bit (counting from zero). It can be used in bitwise operations to set, test, or clear a feature flag associated with that bit, or as part of a larger mask when combined with other values.

In a signed 32-bit integer context, 0x40000000 is a positive number; in unsigned form, it is unchanged. Its binary representation is a 1 followed by 30 zeros. The value is also of note in discussions of 32-bit addressing and memory layout, illustrating the boundary near 1 GiB.

Related topics include hexadecimal notation, memory-mapped I/O, bit masking, and 32-bit addressing.