Chapter 16 - The Future
Quiz
1. Which versions of UNIX are free?
- The best known free version of UNIX is Linux. FreeBSD and NetBSD
are also free. SCO UNIX is free to individuals (i.e. non-commercial
use).
2. How can a company make money selling Open Source software when itís available
for free?
- A company might sell the service of having tested, documented, or
created installation media for software and thus charge for these extras
even though you could download the software from an Internet site for
no charge.
3. How is data associated with an object different from traditional data
in a computer program?
- Traditional data is accessible directly in the data structures in
which they are stored. Data associated with objects can only be accessed
or modified via the objectís methods.
4. How many bits represent an IP address in IPv6?
- An IPv6 address is 128 bits long.
Exercise
Download one of the free versions of UNIX from the Internet and install
it. [level: medium]
- Again, the activity is the lesson.
Project
Determine the last date and time in the year 2038 that UNIX will be able
to represent. [level: medium]
- Integers are represented in 31 bits (1 bit is the sign bit). 2^31-1
is the largest integer value that can be represented (all 1s in the
lower 31 bits) and this value is 2147483647. The UNIX date corresponding
to this value is Tue Jan 19 03:14:07 2038 GMT.
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