### lecture3

```LING 408/508: Programming for
Linguists
Lecture 3
September 2nd
• Today’s Topics:
– Homework 1 Review
– VirtualBox
– Ubuntu install (also your Homework 2)
Homework 1 Review
• Recall the speed of light:
• c = 2.99792458 x 108 (m/s)
1. Can a 4 byte integer be used to represent c exactly?
2. How much memory would you need to encode c
using BCD notation?
3. Can the 64 bit floating point representation (double)
encode c without loss of precision? Explain.
4. The 32 bit floating point representation (float) is
composed of 1 bit sign, 8 bits exponent, and 23 bits
coefficient (24 bits effective). Can it represent c
without loss of precision?
Homework 1 Review
• Recall the speed of light:
• c = 2.99792458 x 108 (m/s)
1. Can a 4 byte integer be used to represent c
exactly?
– 4 bytes = 32 bits
– 32 bits in 2’s complement format
– 231-1 = 2,147,483,647
–
c = 299,792,458
Homework 1 Review
• Recall the speed of light:
• c = 2.99792458 x 108 (m/s)
2. How much memory would you need to
encode c using BCD notation?
– 9 digits
– each digit requires 4 bits (a nibble)
– BCD notation includes a sign nibble
– total is 5 bytes
Homework 1 Review
• Recall the speed of light:
• c = 2.99792458 x 108 (m/s)
3. Can the 64 bit floating point representation
(double) encode c without loss of precision?
Explain.
– Recall significand precision: 53 bits (52 explicitly
stored)
– 253-1 = 9,007,199,254,740,991
– almost 16 digits
Homework 1 Review
• Recall the speed of light:
• c = 2.99792458 x 108 (m/s)
4. The 32 bit floating point representation (float)
is composed of 1 bit sign, 8 bits exponent,
and 23 bits coefficient (24 bits effective). Can
it represent c without loss of precision?
– 224-1 = 16,777,215
– Nope
VirtualBox
• Virtual x86 machine(s)
– install other operating systems (OSs) running inside a
window, we’ll install Ubuntu (Linux) as a Guest OS
• Free application at https://www.virtualbox.org
Ubuntu 14.04 LTS*
under
VirtualBox
under
OS X 10.9.4
*LTS = Long Term Support
Homework 2
• Your homework is to successfully install Ubuntu under
VirtualBox on your computer this week (preferably:
– this is different from partitioning your hard drive, installing
Ubuntu in one of the partitions, and making your machine
dual booting (although you could do that) …
• I’ll walk through the live install Ubuntu here …
• Assume VirtualBox + Extension Pack is installed
– (I’m using version 4.3.14 now)
VirtualBox
• Enable it from VirtualBox Preferences…
VirtualBox
•
•
•
•
ISO image: this is an image of a CD.
Choose 64 bits (recent machine). 32 bits for older machines.
64 bits Mac (for recent Macs) – for booting with a Mac (in BIOS emulation mode)
Skip the
donation
page …
VirtualBox
• The file ubuntu-14.04-desktop-amd64+mac.iso takes considerable time to
• We don’t boot off real cds anymore; the .iso file is a special file that
can be interpreted as a virtual cd
• ISO images:
– Macs can mount ISO images.
– Macs can’t boot off a multitrack ISO image; hence the special
– some versions of Windows can’t mount an ISO image (without extra
software). Install Microsoft’s Virtual CD-ROM Control Panel.
• Next, we need to create the virtual machine on which we’re going
to install Ubuntu on
VirtualBox
• Step 2: in VirtualBox, select New and give new virtual
machine of type Linux a name
dynamically allocated
VirtualBox Disk Image
VirtualBox
Select your
.iso file
VirtualBox
• Confirmation:
VirtualBox
• Boot order, see Settings > System:
– we need to boot off the virtual cd first in order to
install Ubuntu onto the virtual hard disk you created.
(After we’re done installing, we want to go back and
change the boot order so we boot off the hard disk.)
VirtualBox
• Step 3: start your virtual machine, install Ubuntu:
Ubuntu
• Install extension pack:
• No connection:
Ubuntu
• Press on: ask you for name, location, language etc.
Ubuntu
• Restart didn’t work. I shutdown the virtual machine.
And started it again. Logged in and tried Firefox.
Ubuntu
• Since the network wasn’t active on install, Software
Updater has plenty of stuff to do …
do installation.
• May ask you to restart
Ubuntu
– Devices > Insert Guest Additions CD image …
Ubuntu
• Display resolution:
– 640 x 480 until Video Memory is increased in Settings > Display
Ubuntu
• Ubuntu Software Center
– App store
– (full screen to see Search box)
• Software packages
– Terminal: sudo apt-get install <pkg-name>
– sudo prefix: means execute the apt-get command with superuser privileges
(typically needed for packages)
• How to find Terminal: use search
Lock to Launcher
Ubuntu
• Terminal:
The shell has a programming language
– runs a shell: bash
– enter commands: some are built-in to the shell, others are executable
files in specified directories (\$PATH), still others will require apt-get
– simple commands:
•
•
•
•
•
•
•
pwd
ls (ls -a)
cd
mkdir
which name
man name
echo \$SHELL
print working directory
list current directory (-a option: show . (dot) files too)
change directory
create a new directory
the directory where command name is located
display manual page for command name
prints the shell (\$ prefixes a variable)
dpkg –get-selections
– pre-defined environment variables: env
– lots of packages are pre-loaded: wish, python, perl, etc.
```