Machine Language

1
Application Programming Languages

• Machine Language First generation write all
  program instructions in terms of binary code (0s
  and 1s)
• Assembly Second generation
• Close to m/c language,
• Designed for a specific m/c and microprocessors
• Has advantage, but difficult and costly to write
  and learn
• Still used today for writing system software

2

• High-level Languages e.g., C, COBOL, C,
  Basic, FORTRAN, Pascal etc.
• Procedural, textual interface
• Used for different kinds of application programs
• C PC based, efficient programs, portability,
  systems software too
• C - OO version of C used for application
  software as well as system software
• COBOL Business administration to process large
  data files with alphanumeric characters
• Basic Used mainly in education and training, to
  introduce programming concepts to students

3

• Pascal primarily used in computer science
  courses to teach sound programming practices
• FORTRAN processes mainly numeric data,
  scientific and engineering applications
• Visual Basic visual programming tool for
  creating applications running on windows

• Fourth Generation Languages
• Consists of a variety of software tools that
  enable end users to develop software applications
• Minimal technical assistance, graphical interface
• Also increases professional programmers
  productivity
• Tend to be non procedural than conventional
  programming languages

Contd..
4

• No need to specify a strict sequence of steps
• Need only to specify what has to be accomplished
• Some nonprocedural languages use natural
  language processors e.g., speech recognition
• Tightly integrated with GUI screens
• Used to generate complex reports
• Find wide application in development of business
  and commercial application packages
• However for scientific and technical work, the
  third generation languages are still preferred
• Seven categories of fourth generation languages

Contd..
5

• PC software tools general purpose application
  software packages
• for PCs e.g., MS Word, Internet Explorer, MS
  Access
• Query language for retrieving data stored in
  databases, supports a variety of query services
  not defined earlier e.g., SQL
• Report generator
• Extracts data form files/databases,
• Creates customized reports,
• Wide range of formats
• More control and flexibility over formatting than
  query languages

Contd..
6

• RPG III
• Graphics language retrieves data from
  files/databases, displays them in graphical
  format, can perform arithmetic and logical
  operations on data as well e.g., Systat, SAS
  graph
• Application generator
• Contain preprogrammed modules that can generate
  applications, including web sites
• Speeds development greatly
• Creates appropriate program code
• PowerBuilder, MS FrontPage

Contd.
7

• Application software package
• Packages sold/distributed by commercial vendors
  to eliminate/replace in-house custom built
  software
• PeopleSoft, SAP R/3
• Very high-level programming language
• Generate program code with fewer instructions
  than conventional languages
• Productivity enhancement tools for professional
  programmers

8

• Visual Programming
• Construction of software programs by selecting
  and arranging programming objects rather that by
  writing program code
• One of the offshoots of the Object-Oriented
  paradigm
• WebSphere, SunOne Studio 5
• JAVA
• Platform independent, object-oriented programming
  language developed by Sun Microsystems
• Designed to run on any computer or computing
  device
• Not tied to any microprocessor or any OS

Contd.
9

• Even a smart cell phone or PDA can share the same
  Java program
• Can create applications, applets, or
  servelets
• Applets reside on centralized network servers
• Server delivers the requisite applets for
  specific functions
• Provide interactive capabilities for web pages
• Java is a very robust platform
• Can handle text, data, graphics, sound, and video
  all in a single program

10
Hypertext Markup Language (HTML)

• Page description language for creating hypertext
  or hypermedia documents such as web pages
• Uses instructions called tags to specify how the
  text, graphics, sound and video are displayed on
  a web document/page
• Tags are also used to create dynamic links to
  other web pages and objects stored in the same or
  remote computers
• HTML programs are not written manually
• Created using HTML editors such as MS FrontPage

11
eXtensible Markup Language (XML)

• New language for improving the usefulness of the
  web documents
• HTML limits itself to how the text and images
  should be displayed on a web page
• XML describes what the data in those documents
  mean
• This ensures that data elements can be used in
  computer programs for effective manipulation or
  further processing
• In XML, the XML tag specifies whether a number
  represents a price, a date, or a ZIP code
• The XML tags enrich the elements with their exact
  meanings

Contd.
12

• So, computer programs can retrieve specific type
  of data from the web page, manipulate them and
  analyze and interpret the data items on the fly
• Example analyzing on line sales data over a
  period and displaying the same dynamically
• XML has already become a widely used technology
  for web applications
• XML provides a standard format for data exchange
• XML Document Type Definition (DTD) directory of
  standards i.e., RosettaNet an XML dictionary
  developed by 34 leading companies
• Enables the sending and receiving parties to
  describe data the same way

13
Client/Server Computing

• In client/server computing, desktops called
  clients are networked to server computers
• Servers provide the clients with a variety of
  services and capabilities
• Computer processing work is split between these
  two types of machines
• The client is the point of entry

Contd
14

• The server
• provides communication among the clients and
  processes
• stores shared data
• serves up web pages, or
• manages network activities
• The term server refers to both the software
  application and the physical computer on which
  the network software runs
• Servers could be mainframes or midrange computers
  or powerful PCs

15
Client/Server Architecture

• Two-tier client/server architecture the
  simplest client/server network with a client
  networked to a server computer, with processing
  split between the two
• Presentation (UI)/application logic
• Storage
• The application logic is placed within the user
  interface, which also reads and writes directly
  to the database
• Example small business applications

16

• Classic Three-tier architecture
• Presentation UI
• Application Logic (model)
• Storage (persistent storage mechanism)
• The presentation layer is separated
• In two-tier architecture, the integration of UI
  and application logic inhibits software reuse,
  and makes maintenance more complicated
• This is obviated in three-tier architecture
• Also we have the flexibility to change/modify the
  presentation without having to recompile the
  model

Contd..
17

• Multi-tiered (N-tier) client/server architectures
• The work of the entire network is balanced over
  several different levels of servers, depending on
  the kind of service requested
• A client request may be served by a web server,
  which stores and manages web pages
• A particular clients request to have corporate
  info may be passed along to the application
  server

Contd..
18

• The application server handles all application
  operations between a user and an organizations
  back-end business systems
• The application server may reside on the same
  computer as the web server, or may reside on
  another dedicated computer
• Client/server computing enables computing work to
  be distributed across a number of smaller
  machines cost advantage

19
Basic Operating Systems Concepts

• An operating system is software that acts as an
  intermediary between the user (application
  programs) and the hardware
• Two main goals
• - to help the user to run programs in a
  convenient way
• - to run programs in an efficient manner
  resource allocation (memory, CPU, devices,
  storage space,...)
• Shell part of the operating system that accepts
  user commands.
• - text based (e.g. MS DOS)
• - graphical user interface GUI (MS WINDOWS)

Contd.
20

• Kernel to allocate, to use and to free resources
  in an efficient way
• memory management
• processor management
• device management
• storage management
• Memory management
• to allocate memory (look up for free memory
  addresses)
• mono-programming one single program in main
  memory

Contd
21

• multitasking several programs from one user in
  main memory
• multi-programming several programs from several
  users in main memory
• virtual memory additional disk storage is used
  to store (parts) of running programs (backing
  store for main memory)
• - to free used memory
• Processor management
• - to allocate processing time to active programs
  (processes)
• time sharing CPU time is shared by several
  programs (scheduling)

Contd.
22

• multithreading CPU time is shared by several
  threads (program pieces)
• multiprocessing programs can share several CPUs
  either in a symmetric way (SMP) (processors are
  peers) or in an asymmetric way (master-slave
  relationship between processors)
• Device management
• - regulates the traffic between the CPU and the
  I/O devices
• device drivers low-level software to initiate
  and to control the I/O to and from an I/O device
• spool (Simultaneous Peripheral Operations
  On-line) printer output is sent to disk storage
  in order to solve the problem of concurrent
  printing

Contd.
23

• concurrent printing on one printing device
• cancel unwanted print jobs
• change print job priorities
• memory can be freed during printing process

24

• Storage management (information management)
• to organise and retrieve the information stored
  on storage media (tapes, disks, )
• allocation of storage capacity
• remove of files, directories
• file system structure
• Directories
• files, Inodes
• security