Know A system board contains a CPU, RAM, expansion bus, CMOS, ROM BIOS, clock, and keyboard controller, and may have additional interfaces built into it. Know where these components are located on the system board and be able to identify them by sight. A CPU, or central processing unit, provides the brain functions for the entire computer. The expansion bus is the physical wire that the data travels on. The data bus is the specific route that the data takes to any given device.
RAM is random access memory.
RAM is erased every time the system is turned off. ROM is read-only memory. This memory is used for the long term storage of programs and data as firmware on a chip. It runs the POST and interfaces with CMOS and the operating system. A CRT uses electrons fired at a phosphor-coated screen to display a pixel.