A typical programming task can be divided into two phases: Problem-solving phase: produce an ordered sequence of steps that describe the solution of the problem this sequence of steps is called an algorithm. Implementation phase: implement the program in some programming language. Every algorithm must satisfy the following criteria: Input. Zero or more quantities are externally supplied. Output. At least one quantity is produced. Definiteness. Each instruction must be clear and unambiguous(Unique meaning). Finiteness. An algorithm terminates in a finite number of steps. Effectiveness. Every instruction must be basic enough to be carried out than, means not so complex. An algorithm is a finite set of steps defining the solution of a particular problem. What is the difference between an algorithm and a program?  a program is an implementation of an algorithm to be run on a specific computer and operating system. an algorithm is more abstract – it does not deal with machine-specific details – think of it as a method to solve a problem. What is a good algorithm? Efficient algorithms are good, we generally measure the efficiency of an algorithm based on: Time: the algorithm should take minimum time to execute. Space: the algorithm should use less memory. DIFFERENCE BETWEEN ALGORITHM AND PSEUDOCODE? An algorithm is a well-defined sequence of steps that provides a solution for a given problem, while pseudocode is one of the methods that can be used to represent an algorithm. While algorithms can be written in natural language, pseudocode is written in a format that is closely related to high-level programming language structures. But pseudocode does not use specific programming language syntax and therefore could be understood by programmers who are familiar with different programming languages. Additionally, transforming an algorithm presented in pseudocode to programming code could be much easier than converting an algorithm written in natural language. But pseudocode does not use specific programming language syntax and therefore could be understood by programmers who are familiar with different programming languages. Additionally, transforming an algorithm presented in pseudocode to programming code could be much easier than converting an algorithm written in natural language.

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Farzana Shah
(BS-IT, MBA-HRM)
Lecturer : (Computer Science)
Al
orithm
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Contents
LECT # 2
Algorithm
 Definition of algorithm
 Need of algorithm
 Designing of algorithm
 Pseudocode
 Examples
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ALGORITHMS AND Program
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A typical programming task can be divided into
two phases:
Problem solving phase
produce an ordered sequence of steps that describe
solution of problem
this sequence of steps is called an algorithm
Implementation phase
implement the program in some programming
language
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Algorithm(noun):
A set of steps to accomplisha task
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Analgorithmdescribesthestepby
stepaction to solve a problem.
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Analgorithmhasa welldefined
sequenceof steps, it givesyouan
output,andit willeventually
terminate.
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Analgorithmis a precisestep-by-
stepplanfora computational
procedure that possiblybeginswith
aninput valueandyieldsanoutput
valuein a finite numberofsteps in
orderto solve a particular problem
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Analgorithm is a self-containedstep-by-stepset of
operationsto be performedto solve a specific
problemor a class ofproblems.
A computerprogramis a sequence ofinstructions
that complytherulesofa specificprogramming
language , written to performa specifiedtaskwith
a computer.
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Algorithms
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An algorithm is a finite set of steps defining the
solution of a particular problem.
Need not to belong one particular language
Sequence of English statements can also be algorithm
It is not a computer program
An algorithm can be expressed in English like
language, called pseudocode, in a programming
language or in the form of flowchart.
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WhyAlgorithm is needed?
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Computer Program ?
Set of instructions to perform some specific task
Is Program itself a Software ?
NO, Program is small part of software.
Software merely comprises of Group of Programs
(Source code),
Code: refers to statements that are written in any
programming language as machine code or C code.
•Code is some time interchangeably used with
program.
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11. z WhyAlgorithm is needed?FARZANASHAHICS
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• Programming is both tedious and exciting.
Tedious because like spoken languages
programming languages also have so many
demanding rules.
Exciting because writing program provides the
programmer with the chance to create
something new also gives challenges of solving
a problem.

12. z WhyAlgorithm is needed?
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It is very difficult to write direct programs in
any language, just like you can not start
constructing building without the design of
building.
For constructing a building you need design of
building, similarly for writing a large or good
program you need algorithm.
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13. z Program design
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Program Design Process has 2 phases:
Problem Solving Phase
Creates an algorithm that solves the problem
Implementation (Coding) Phase
Translates the algorithm into a programming
language
Algorithm
Problem Program
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14. z Algorithm Vs Program
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What is the difference between an algorithm and a program?
a program is an implementation of an algorithm to be run on a
specific computer and operating system.
an algorithm is more abstract – it does not deal with machine
specific details – think of it as a method to solve a problem.
•What is good algorithm?
Efficient algorithms are good, we generally measure efficiency of
an algorithm on the basis of:
1.Time: algorithm should take minimum time to execute.
2.Space: algorithm should use less memory.
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Algorithm Specification
Every algorithm must satisfy the following
criteria:
Input. Zero or more quantities are externally supplied.
Output. At least one quantity is produced.
Definiteness. Each instruction must be clear and
unambiguous(Unique meaning).
Finiteness. An algorithm terminates in a finite number of steps.
Effectiveness. Every instruction must be basic enough to be carried
out than, means not so complex.
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16. z Pseudocode
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 First produce a general algorithm (one can
use pseudo code)
 Refine the algorithm successively to get
step by step detailed algorithm that is very
close to a computer language.
 Pseudo code is an artificial and informal
language that helps programmers develop
algorithms. Pseudo code is very similar to
everyday English.
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DIFFERENCE BETWEEN ALGORITHM
AND PSEUDOCODE?
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An algorithm is a well defined sequence of steps that
provides a solution for a given problem, while a
pseudocode is one of the methods that can be used to
represent an algorithm.
While algorithms can be written in natural language,
pseudocode is written in a format that is closely related
to high level programming language structures.
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DIFFERENCE BETWEEN ALGORITHM
AND PSEUDOCODE?
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But pseudocode does not use specific programming
language syntax and therefore could be understood by
programmers who are familiar with different
programming languages.
Additionally, transforming an algorithm presented in
pseudocode to programming code could be much
easier than converting an algorithm written in natural
language.
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Informal definition of an algorithm
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ALGORITHM
REPRESENTATION
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Example 1
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Average Of Two numbers
Input: Two numbers
1.Add the two numbers
2.Divide the result by 2
3.Return the result by step 2 2 End
Write an algorithm that reads two numbers and prints
their average.
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Example 2
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Pass/FailGrade
Input: One number
1.if (the number is greater than or
equal to 40) then
1.Set the grade to “pass” else
2.Set the grade to “fail” End if
2.Return the grade End
Write an algorithm that reads marks number
and prints whether student is pass or fail.
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Example 3
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Marks range Grade
>=80 A
>=70 &<80 B
>=60 &<70 C
>=50 &<60 D
<50 F
Write an algorithm that read a numbers and prints
the grade of student.
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Algorithm for Grading
AlgoForGrade
Input: One number
1.if (the number is between 80 and 100, inclusive)
then
1. Set the grade to “A” End if
2.if (the number is between 70 and 79, inclusive)
then
1. Set the grade to “B” End if
Continues on the next slide
Solution
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3. if (the number is between 60 and 69,
inclusive) then
3.1 Set the grade to “C” End if
4. if (the number is between 50 and 59, inclusive)
then
1. Set the grade to “D” End if
5. If (the number is less than 50) then
1. Set the grade to “F” End if
6. Return the grade End
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PSEUDOCODE & ALGORITHM
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 Example : Write an algorithm to determine a student’s final
grade and indicate whether it is passing or failing. The final
grade is calculated as the average of four marks.
EXAMPLE 4
Pseudo code:
Input a set of 4 marks
Calculate their average by summing and
dividing by 4
if average is below 50 Print “FAIL”
else
Print “PASS”

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 DetailedAlgorithm
Step 1:
Step 2:
Step 3:
Input M1,M2,M3,M4
GRADE (M1+M2+M3+M4)/4
if (GRADE < 50) then Print
“FAIL” else
Print “PASS”
endif
PSEUDOCODE & ALGORITHM
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28. z
Question &
Answer
Farzana Shah
Lect: Computer Science
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