Computers

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Computers

• Hardware and Software

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Acknowledgments
Thanks to the following web site for the images
used in this presentation

• Wikipedia
• http//microsoft.toddverbeek.com
• http//www.webopedia.com
• http//www.engin.umd.umich.edu/
• http//www.dell.com
• http//www.intel.com
• http//www.apple.com
• http//www.ibm.com
• http//homepages.feis.herts.ac.uk/msc_ice/unit2/
• http//www.howstuffworks.com

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Computer Layers
Hardware BIOS Operating System Software Pr
ogramming languages
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Computer Layers
Hardware BIOS Operating System Software Pr
ogramming languages
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Looking inside a computer
Computers come in different shapes and sizes,
from small laptops (notebooks), desktops to
mainframe computers. They all share however the
same internal architecture!
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Computer basic scheme
Input devices
Output devices
CPU
Storage
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The motherboard backbone of the computer
Power supply connector
Slot for memory RAM
Hard drive connectors
Slot for CPU
Input/Output Keyboard, Mouse,
Extension cards Video, sound, internet
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The Central Process Unit (CPU) The brain of
the computer
CPUs are getting smaller, and can include more
than one core (or processors).
CPUs get hot, as their internal components
dissipate heatit is important to add a heat sink
and fans to kep them cool.
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Memory Working Space
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Storage
Hard drive
Floppy disk
CD or DVD
USB key
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Communicating with a computer
Screen
Mouse
Keyboard
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Some Input/Output Interfaces
Video cards
Sound card
Ethernet card
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Hardware communication buses
Cache
CPU
(33 to 1333 MHz)
Backside bus
(speed of processor)
(33 to 1333 MHz)
(66 MHz)
ISA devices
ISA bus
(33 or 66 MHz)
(8.3 MHz)
(up to 300 MHz)
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Hardware communication buses
The memory bus
a 16 bit bus
CPU
RAM

• Communication between the CPU and the RAM is
  defined by
• the CPU speed
• The RAM speed
• The number of bits transferred per cycle

Other buses USB, Firewire, PCI Express,
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Computer Layers
Hardware BIOS Operating System Software Pr
ogramming languages
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BIOS Basic Input/Output Layer

• BIOS refers to the firmware code usually stored
  on the PROM, EPROM or flash drive that is run by
  a computer when first powered on.
• BIOS performs three major tasks
• First, the Power On Self Tests (POST) are
  conducted. These tests verify that the hardware
  system is operating correctly.
• - Second, the BIOS initiates the different
  hardware component of the system, scanning their
  own ROM or PROM.
• - Third, the BIOS initiate the boot process. The
  BIOS looks for boot information that is contained
  in file called the master boot record (MBR) at
  the first sector on the disk. Once an acceptable
  boot record is found the operating system is
  loaded which takes over control of the computer.

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Computer Layers
Hardware BIOS Operating System Software Pr
ogramming languages
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The operating system
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The operating system
Definition found on Wikipedia An operating
system (OS) is the software that manages the
sharing of the resources of a computer and
provides programmers with an interface used to
access those resources
Most common operating systems - DOS (desktops,
laptops) - Unix and variants, including Linux
(servers) - MacOS
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The operating system

• Operating systems can be classified as follows
• multi-user Allows two or more users to run
  programs at the same time.
• -multiprocessing Supports running a program on
  more than one CPU.
• -multitasking Allows more than one program to
  run concurrently.
• multithreading Allows different parts of a
  single program to run concurrently.

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The operating system
Memory management Current computers organize
memory resources hierarchically, from registers,
CPU cache, RAM and disks.
The virtual memory manager coordinates the use of
these resources by tracking which one is
available, which is to be allocated or
deallocated and how to move data between
them. If running processes require significantly
more RAM than is available, the system may start
thrashing.
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The operating system
Most operating systems come with an application
that provides a user interface for managing the
operating system, such as a command line
interpreter or graphical user interface (GUI).
Operating systems provide a software platform on
top of which other programs, called application
programs, can run. Your choice of operating
system determines the applications you can run.
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Computer Layers
Hardware BIOS Operating System Software Pr
ogramming languages
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Application Software
Application software is a class of computer
software that uses the capabilities of a computer
to a task that the user wishes to perform. The
term application refers to both the application
software and its implementation. Typical
examples of software applications are word
processors, spreadsheets, and media players.
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Computer Layers
Hardware BIOS Operating System Software Pr
ogramming languages
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Programming languages
A programming language is an artificial language
that can be used to control the behavior of a
machine, particularly a computer.
Programming languages are used to facilitate
communication about the task of organizing and
manipulating information, and to express
algorithms precisely.
(An algorithm is a list of well-defined
instructions for completing a task that is,
given an initial state, it will proceed through a
well-defined series of successive states,
eventually terminating in an end-state. The
transition from one state to the next is not
necessarily deterministic some algorithms, known
as probabilistic algorithms, incorporate
randomness)
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Programming languages
There are many, many programming languages, and
new ones appear every year.
(http//www.engin.umd.umich.edu/CIS/course.des/cis
400/)
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Programming languages

• Three main levels of programming languages
• Machine languages refers to the "ones and
  zeroes" that processors use as instructions. Give
  it one pattern of bits (such as 11001001) and it
  will add two numbers, give it a different pattern
  (11001010) and it will instead subtract one from
  the other.
• Assembly languages is as close as you can come
  to writing in machine language, but has the
  advantage that it's also human-readable... using
  a small vocabulary of words with one syllable,
  such as
• MOV A, B

-High level languages A vocabulary and set of
grammatical rules for instructing a computer to
perform specific tasks. Each language has its own
set of keywords and its own syntax.
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Programming languages Interpret or Compile?

• Regardless of what language you use, you
  eventually need to convert your program into
  machine language so that the computer can
  understand it. There are two ways to do this
• interpret the program through an interpreter
• compile the program through a compiler

The main disadvantage of interpreters is that
when a program is interpreted, it runs slower
than if it had been compiled.
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Programming languages Interpreters

• An interpreter is a program that either
• - executes the source code directly (type I)
• translates source code into some efficient
  intermediate representation and immediately
  executes this (type II)
• - is invoked to explicitly execute stored
  precompiled code made by a compiler which is part
  of the interpreter system (type III)

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Programming languages Compilers
Source Code
Source Code
Source Code
Source Code
Compile
Object File
Object File
Object File
Object File
Runtime Library
Executable Program
Link
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Programming languages Compilers
A compiler is a program that translates source
codes into object codes. The compiler derives its
name from the way it works, looking at the entire
source code and collecting and reorganizing the
instructions.
Thus, a compiler differs from an interpreter,
which analyzes and executes each line of source
code successively, without analyzing the entire
program.
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Programming languages Examples
Interpreted languages - Perl, Python, Matlab
(type II) - Java (type III) Compiled
languages - Fortran - C, C - Pascal -
Basic - Cobol - ADA