Download OPERATING SYSTEMS

OPERATING SYSTEMS
The various hardware pieces that are assembled by an organization to enhance its
computerized accounting information systems need an operating system, which is “…an
integrated system of programs that manages the operations of the CPU, controls the
input/output and storage resources and activities of the computer system, and provides
various support services as the computer executes the application programs of
users.”(O’Brien, 2004:508). Hove,Mutungwazi and Totev(1996:59) adds that OS is “…a
piece of computer software which intermediates between the user and
machine(hardware). It is part of the control software.” And “…a master control program
which controls the functions of a computer system as a whole and the running of
application programs.” (Anderson, 1994:399)
The operating system is part of the software a computer uses in conjunction with /
interfacing the user and the two are the most important part of the computer system, “No
matter how state-of-the-art the computer is, it is of little value without the right software.”
(Bodnar and Hopwood, 1998:120) In fact it is best to select the software before selecting
the hardware. The software is made up of three categories: operating systems and their
extensions; user application programs and computer languages (translator).
The purpose of an OS is :
 to maximize productivity of a computer system by operating it in the most
efficient manner.
 To minimize the amount of human intervention during processing,
 To assist in accessing a network, data capture, saving and retrieving files,
printing/displaying output
 To boot and activate the computer system before operations.
Exhibit 1.1 shows OS:
End-users
Application Software/ Program
Operating System/ System Software
Hardware
Operating System/ System Software
Application Software/ Program
End-users
Adapted from (O’Brien, 2004:510 and Bodnar and Hopewood, 1998: 120)
The OS embraces the hardware with the application program in between the hardware
and end-users. Users are directly involved in the design of systems so they need to
understand which programs are easy or difficult to use, (Lucas, 1997: 202) As an enduser, the application program you use e.g Pastel, is controlled by the OS whose functions
are three according to (Bodnar and Hopewood, 1998) or five according to (O’Brien,
2004:510). These are: accounting and security, management and allocation of computer
system resources; and software services to user application programs. O’Brien’s five
functions are: providing a user interface, resource management, task management, file
management, utilities and support services.
User interface: Allows user to communicate with OS enabling user to load programs,
access files, do other tasks eg. Command-driven, menu-driven, graphical user interface
(GUI) i.e. the trend is , “… moving away from the entry of brief end-user commands
…or selection of choices from menus of options.” The trend is on use of “icons, bars,
buttons, boxes and similar images.” GUis rely on pointing devices eg. Electronic mouse,
touch pad.
Resource management: OS uses resource management programs to manage the hardware
and networking resources of a computer system i.e its CPU, memory, secondary storage
devices, tele-communication processors and input/output peripherals. It incorporates
accounting and security of the whole system. For most multi-users, OS, have securityto
limit “access to the system and its resources, protects files, and …memory.” (Bodnar and
Hopewood, 1998:120).
Each user is assigned a user account allowing user to log on /log out, by use of a user
account number or user I.D. and log-on password. When logged on, the system monitors,
records and limits the activities of the user. Its like an Audit trail.
Systems personnel create these user accounts and pre-define user limits e.g what
resources are available to users such as:
i)
Maximum amount of disk storage user can use
ii)
Maximum number of files user can create
iii)
Maximum number of lines or pages user can print
iv)
Maximum amount of CPU time user can use
v)
Maximum amount of primary memory available to user.
It further limits user on:
a) Access to magnetic tape drives
b) Access to particular files or programs.
File management: In terms of security levels, users are assigned levels, eg 1-10 with 1
being the highest level, 10 the lowest level. Security level number 4 enjoys what security
level number 5 can do but security level number 4 may not have privileges due to 5.
File creation and protection are included in the security system eg. “…a user can create,
modify and erase files.” (Bodnar and Hopewood,1998:121).eg:
Public files allows any user access to file, while private files allow no one else access to
file; and semi-private files allows some users with the correct password access to files.
User also specifies if others can or cannot modify, erase these accessible files. Hence the
OS keeps “directories of information about the location and characteristics of files stored
on a computer’s secondary storage devices.” (O’Brien, 2004: 511)
Task management: The OS manages “ the accomplishment of computing tasks of endusers.” Each task is given a slice of a CPU’s time and swapping of other tasks with those
that are allocated time to allow for “concurrent processing” in a multi-programming and
or time sharing set up. (Bodnar and Hopewood, 1998:121) Time sharing allows”more
than one user to concurrently interact with or execute programs on the computer.” Task
management involves a “multi-tasking capability where several computing tasks can
occur at the same time.”
Efficiency of multi-tasking depends on “the processing power of a CPU and the virtual
memory and multi-tasking capabilities of the OS it uses.” Hence we find that microcomputers, mid-range, mainframe OS have multi-tasking capabilities.
Response time of the system is affected by the number of users demanding use of the
CPU hence there is a slow down of the CPU felt by users. You have complained of a
slow response time of the Internet at one time. Its because there are too many users using
the sever at once.
Another example of multi-tasking is “ concurrent execution” of more than one program.
When you open an Excel file, are researching on Google and typing a report on
WordPerfect, it is concurrent execution. These are windows (Bodnar and
Hopewood,1998: 122) that appear on the VDU. In the foreground task is the active
program while those programs not being executed are in the background task.
Popular Operating Systems:
Windows 2000 Microsoft, Solaris 8 UNIX, Netware 5.1 Novel and Linux 6.1 Red Hat
Software.
Computer languages.
According to Lucas (1997: 203) software generations are as follows:
Software
generation
First
Period
Software
1950-58
Second
1958-64
Third
1964-70
Fourth
1970-80
Machine language, assembly language where
binary codes unique to each computer were
used
Assembly language which reduced
difficulties in writing machine language,
used translator language called assemblers
which allowed computers to convert the
instructions of such language into machine
instruction a.k.a symbolic languages as
symbols are used or mnemonics ( memory
aids) to represent codes, storage locations,
data elements. High level languages, batch
OS, dedicated on-line systems and
experimental time-sharing were developed.
Preponderance of higher-level languages,
expansion of packaged systems, OS
mandatory, mixed on-line and batch
applications, virtual memory, time-sharing
systems. Has less rigid rules, forms and
syntaxes, instructions are called statements.
Each macro-instruction generates several
machine instructions through use of
computers/ interpreters.
Non-procedural and conversational than prior
languages. Users and programmers specify
what outcome they want; natural languages
are 4GLs that are close to English/ human
languages; linked to Artificial Intelligence,
virtual memory OS program for PCs, Object
oriented languages, Open systems.