Your new laptop features 4 GB of system RAM and a built-in video card. The default video memory set is 512 MB. How much RAM is available for use by the processor?

Many laptops have shared video memory, which means that system RAM is split between the processor and the video card. The amount of RAM available for video on these systems is controlled in the BIOS/UEFI. The processor cannot access anything reserved for the video card. In this scenario, reducing half a gigabyte from 4 GB yields 3.5 GB for the CPU.