Question

An external computer flash drive can hold 1 gigabytes of data how many byes is this

Answer 1

There are 1000000000 bytes in a gigabyte.

Answer 2

The prefix "giga..." means "billion".

When you're talking about data, though, the actual number
is always a power of 2 . 

               1 gigabyte = actually  2³⁰  =  1,073,741,824 bytes

               but we talk about it as if it's  1,000,000,000 bytes.