A coworker asks for your help troubleshooting an issue. They have installed a new copy of Windows 10 Professional and noticed the operating system only shows 4GB of memory when there is 16GB installed in the computer. What is most likely the issue?
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 CPU and ALU architectures are those that are based on registers, address buses, or data buses of that size 32-bit microcomputers are computers in which 32-bit microprocessors are the norm