What is the size of the reserved memory area?

ANS:B - 384 kb

In DOS memory management, the upper memory area (UMA) refers to memory between the addresses of 640 KB and 1024 KB (0xA0000-0xFFFFF) in an IBM PC or compatible. IBM reserved the uppermost 384 KB of the 8088 CPU's 1024 KB address space for ROM, RAM on peripherals, and memory-mapped input/output.

The first memory segment (64 KB) of the conventional memory area is named lower memory or low memory area.

In the design of the PC, the memory below 640 KB was for random-access memory on the motherboard or on expansion boards. The remaining 384 KB beyond it, called the upper memory area (UMA), was reserved for system use and optional devices. UMA was used for the ROM BIOS, additional read-only memory, BIOS extensions for fixed disk drives and video adapters, video adapter memory, and other memory-mapped input and output devices.