From QB64 Wiki
The memory segment is the hexadecimal byte address in relation to a segment register.
The value in a Segment register is multiplied by 16 or shifted one hexadecimal byte to the left(this adds an extra 0 to the end of the hex number). The value in the Offset register is added to it. So, the Absolute address for any combination of Segment and Offset is found using the formula:
- AbsoluteMemoryAddress = (Segment value * 16) + Offset value
Segment Address = F0000 ← shifted left Offset Address = + FACE ------ FFACE or 1,047,246
The Offset value is the position of a value after the segment address. Many pairs can be used to refer to the same memory position.