Transcript chapter 7: computer software

CHAPTER 7:
COMPUTER SOFTWARE
Major Types of Software
System software:
– generalized programs
that manage the
computer’s resources
Application software:
– Programs written for a
specific application to
perform functions
specified by end users
Operating System Functions
• Allocation and Assignment
– Allocates resources to applications
– Controls primary memory allocation
• Scheduling
– Scheduling processing, inputs and
outputs
• Monitoring
– Keeps tracks of users and jobs
Managing Multiple Users (1)
• Multiprogramming/Multitasking
– Allows two or more programs to share resources
of same computer
– CPU executes one program while managing input
and output of other program
• Multithreading
– The capability of an operating system to execute
different parts of the same program (threads) at the
same time
Managing Multiple Users (2)
• Virtual Memory
– Creates efficiency by dividing the programs into small
sections (pages) and reading them into memory only when
needed
• Timesharing
– Allows computer resources to be shared by many users
simultaneously by having the CPU spend a fixed amount of
time on each user’s program
• Multiprocessing
– Allows computer to execute two or more instructions
simultaneously in a single computer system by using
multiple CPUs
Language Translation
• Compiler
– Translates source code into object code all at one time
• Interpreters
– Translates source code one line at a time
Operating Systems
Windows XP
Versions for home & corporate; supports Internet and
multimedia; improved networking, security, and
corporate management capabilities
Windows ME, 98 &
95
32-bit operating system; GUI; Multitasking;
Networking capabilities
Windows 2000
32-bit operating system; Multitasking; Multiprocessing;
Networking; Internet services
Windows CE
Paired-down for handheld computers, wireless
communication devices
Palm OS
Palm compatible handheld computers/devices
Operating Systems (continued)
UNIX
For powerful PCs, workstations, midrange computers.
Multitasking; Multiuser Processing; Networking.
Portable to various computer hardware platforms
Linux
Free, reliable alternative to Unix & Windows. Runs on
many platforms; open source code
Mac OS
For Macintosh computers; Multitasking; Networking;
Powerful multimedia capabilities
Programming Languages
• First Generation: Machine Language
– All instructions written in binary (0s and 1s)
• Second Generation: Assembly languages (1950s)
– Substitutes mnemonics for numeric codes
• Third Generation: since mid 1950s
– Instructions more English-like
• Fourth Generation: since late 1970s
– Application Specific Language
Third-Generation Languages
• FORTRAN (FORmula TRANslator)
– Scientific & Mathematical applications
• COBOL (COmmon Business Oriented Language):
– Business applications; Process large data files; alphanumerics
• BASIC (Beginners All-purpose Symbolic Instruction Code) &
Pascal:
– Used to teach programming; quite easy to use
• C and C++
– Efficient and portable
– C++ is object oriented version of C
Fourth-Generation Languages (1)
• Query Languages
– Structured Query Language (SQL)
• Report Generators
– Create customized reports
• Graphics Languages
– Retrieve data and display them graphically
• Application Generators
– Generator creates logic and code for application
• Very high-level programming languages
– Professional programmer productivity tool
Fourth-Generation Languages (2)
• Application software packages
– Word processing, spreadsheets, data
management, presentation graphics, web
browsers, email, groupware
– Integrated software packages and suites
– Software for specific tasks (tax programs,
accounting packages)
Software for Enterprise
Integration
• Enterprise Software
– Enterprise Resource Planning (ERP)
– Integrated modules (sales, accounting, production, etc.)
that allow data to be used by multiple functions and
business processes
• Middleware
– Software to connect applications and allow them to
share data
• Enterprise Application Integration Software
– Software that ties together multiple applications
Tools for Software Development
• Object-Oriented Programming
• New Languages
– JAVA, HTML, XML
Object-Oriented Programming
• Combines data & procedures into a single
object
• Program sends message to object to perform
embedded procedure
• Object’s data encapsulated from rest of
system
• Creates reusable code
JAVA
• Sun Microsystems object-oriented programming
language
• Platform independent
• Use Java to create applets
– tiny program to execute small function
– Applets downloaded from centralized server
HTML and XML
• HTML
• XML
– eXtensibe Markup Language
– Describes structure of document & its data
• XBRL
– eXtensible Business Reporting Language
– Designed to make financial statements & reports easier
to prepare and consistent
• XHTML
– eXtensible Hypertext Markup Language
– Hybrid of HTML and XML
Managing Software Assets
• Rent Versus Buy Versus Build
– ASP (application service provider)
• Company that provides software (and sometimes
hardware) that is rented over the network
• Maintenance
• Selecting Software
– Appropriateness, Efficiency, Compatibility and
Support