Types of OS:
Operating System can also be classified as,
Single User Systems
Multi User Systems
Single User Systems:
Provides a platform for only one user at a
They are popularly associated with Desk Top
operating system which run on standalone
systems where no user accounts are
Provides regulated access for a number of users by
maintaining a database of known users.
Refers to computer systems that support two or more
Another term for multi-user is time sharing.
Ex: All mainframes and are multi-user systems.
Today's Topic: Problem Solving Techniques
We will learn
Problem Statement help diagnose the situation so that
your focus is on the problem, helpful tools at this stage
include Algorithms and flowcharts for identifying the
expected steps of a process. Therefore to solve any
Collect and analyze information and data
Talk with people familiar with the problem
If at all possible, view the problem first hand
Confirm all findings
The algorithm is part of the blueprint or plan for the
computer program, an algorithm is:
“An effective procedure for solving a class of problems
in a finite number of steps.”
Every algorithm should have the following 5
To find largest of three numbers
Read 3 numbers: num1, num2, num3
if num1 > num2 then go to step 5
if num2 > num3 then
print num2 is largest
print num3 is largest
goto step 6
if num1 > num3 then
print num1 is largest
print num3 is largest
Example: One of the simplest algorithms is to find the
largest number in an (unsorted) list of numbers.
Assume the first item is largest.
Look at each of the remaining items in the list and if
it is larger than the largest item so far, make a note
The last noted item is the largest in the list when
the process is complete.
Formal description: Written in prose but much closer to
the high-level language of a computer program, the
following is the more formal coding of the algorithm in
pseudo code (find the largest number in an
(unsorted) list of numbers)
Input: A non-empty list of numbers L.
Output: The largest number in the list L.
largest ← L0 for each item in the list L, do
if the item > largest, then
largest ← the item
What is a Flowchart?
The flowchart is a means of visually presenting the flow
of control through an information processing systems,
the operations performed within the system and the
sequence in which they are performed.
It is a graphic representation of how a process works,
showing, at a minimum, the sequence of steps.
Flowcharts are generally drawn in the early stages of
formulating computer solutions.
Guideline for drawing a flowchart:
Flowcharts are usually drawn using some standard
symbols; Some standard symbols, which are frequently
required for flowcharting many computer programs are
A set of useful standard Flowchart
use it to represent an event which occurs automatically.
Rectangle or box
use it to represent an event which is controlled within
the process. Typically this will be a step or action which
use it to represent a decision point in the process.
use it to represent a point at which the flowchart
connects with another process.
ADVANTAGES OF USING
Communication: Flowcharts are better way of
communicating the logic of a system
Effective analysis: Problem can be analyzed in more
Proper documentation: Flowcharts serve as a good
Efficient Coding: Flowcharts act as a guide or blueprint
during the systems analysis and program development
ADVANTAGES OF USING
Proper Debugging: Flowchart helps in debugging
Efficient Program Maintenance: The maintenance of
operating program becomes easy with the help of
Flowchart for finding the sum of first five natural numbers
( i.e. 1,2,3,4,5):
Flowchart to find the sum of first 50 natural numbers.
Flow Chart to find largest of two numbers:
Read A, B
Is A > B
Flowchart to find the largest of
three numbers A,B, and C:
LIMITATIONS OF USING
Complex logic: Sometimes, the program logic is quite
complicated. In that case, flowchart becomes complex
Alterations and Modifications: If alterations are
required the flowchart may require re-drawing
Reproduction: As the flowchart symbols cannot be
typed, reproduction of flowchart becomes a problem.
Draw a flowchart to depict all steps that you do
reach your college.
Draw Flowchart for Linear search.