Marco Simamora

COMPUTER SOFTWARE

Posted: October 1st 2012


LEARNING OBJECTIVES

•          Differentiate between the two major types of software

•          Describe the general functions of the operating system

•          Differentiate among types of operating systems and describe each type

•          Identify three methods for developing applications software

The Software Crisis

•          New software applications cannot be developed fast enough to:

Ø  Keep up with dynamic business environment

Ø  Keep pace with rapid hardware advances

•          Lag in software development limits IS capabilities

Ø  The Software Crisis (continued)

•          In addition to new application development, existing software must also be maintained (80% IT personnel effort towards maintenance).

•          Increasing complexity leads to the increased potential for “bugs.”

•          Testing and “debugging” software is expensive and time-consuming.

Software Fundamentals

•          Some basic terms…

Ø  Computer programs – sequences of instructions for the computer

Ø  Stored program concept – instructions written in programs are stored and executed by CPU when needed

Ø  Programming – process of writing (or coding) programs

Ø  Programmers – individuals who perform programming

Systems Software

Ø  Instructions that manage the hardware resources

Application Software

Ø  Instructions that perform specific user tasks

System Software

•          System software is software that:

Ø  Controls and supports the computer system’s activities

Ø  Supports application software by directing the computer’s basic functions

Ø  Facilitates program development, testing, and debugging

Ø  Is independent of any specific type of application

•          System Control Programs

Ø  Control use of all system resources (hardware, software, data); operating system

•          System Support Programs

Ø  Specialized support capabilities

 

System Control Programs

•          Operating System – main system control program

Ø  supervises the overall operation of the computer

Ø  allocates CPU time and main memory to programs running on the computer

Ø  provides an interface between the user and the hardware

 

Operating System Services

•          Process management – manage program(s) running on processor

Ø  Multitasking or Multiprogramming – managing two or more tasks, or programs, running on the computer system at the same time

Ø  Multithreading – type of multitasking; run two or more tasks from the same application simultaneously

Ø  Timesharing – many users share same CPU, each using a different input/output terminal

Ø  Multiprocessing – simultaneous processing with multiple CPUs

Ø  Operating System Services (continued)

•          Virtual memory – simulates more main memory than actually exists in the computer system

•          File management and security – managing the arrangement of, and access to, files held in secondary storage

•          Fault tolerance – system can produce correct results and continue to operate even in the presence of faults or errors

•          User interface – allows users to have direct control of visible objects (icons) and actions that replace complex command syntax

 

Types of Operating Systems

•          Departmental Server Operating Systems

Ø  Support hundreds of concurrent users

Ø  UNIX, Linux, Windows 2000, Windows XP, Novell NetWare

•          Enterprise Operating Systems

Ø  Support thousands of concurrent users; millions of transactions per day

Ø  IBM’s OS/390, IBM’s VM (Virtual Machine), IBM’s VSE (Virtual Storage Extended), and IBM’s OS/400

 


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