Answer Description

Many operating systems come in 32-bit and 64-bit versions. 32-bit versions are becoming less common but can still be found. 32-bit operating systems can only address up to 4GB of memory.

Wikipedia

In computer architecture, 32-bit integers, memory addresses, or other data units are those that are 32 bits (4 octets) wide. Also, 32-bit central processing unit (CPU) and arithmetic logic unit (ALU) architectures are those that are based on registers, address buses, or data buses of that size. 32-bit microcomputers are computers that use 32-bit microprocessors.