3. By wikipedia definition:
▪ an algorithm is a sequence of finite instructions,
often used for calculation and data processing.
▪ It is formally a type of effective method in which a
list of well-defined instructions for completing a
task will, when given an initial state, proceed
through a well-defined series of successive states,
eventually terminating in an end-state.
5. First documented algorithm by Euclid (300 B.C.)
to compute greatest common divisor (gcd).
1. Let A and B be integers with A > B 0.
2. If B = 0, then the gcd is A and the algorithm ends.
3. Otherwise, find q and r such that
A = qB + r where 0 r < B
Note that we have 0 r < B < A and gcd(A,B) = gcd(B,r).
Replace A by B, B by r. Go to step 2.
6. Example No. 2:
Find the greatest common divisor of A=40, B=15;
using Euclidean algorithm;
A = 2B + 10 A = 15 ; B = 10
A = 1B + 5 A = 10 ; B = 5
A = 2B + 0 A=5;B=0
gcd is 5
7. There are three properties of algorithm that
must have to consider in solving a certain
problem in programming:
Absence of Ambiguity
Input and Output Definition
Scope of Definition
The execution of a programmed algorithm must
be complete after a finite number of operations
have been performed. Otherwise, we cannot
claim that the execution produces a solution.
9. Absence of Ambiguity
The representation of every step of an algorithm
should have a unique interpretation which also
understand by the human.
It is convenient to deal with algorithms presented
in notational with sparse detail:
▪ Pseudo code
10. Sequence of Definition
The sequence in which the steps of the algorithm
are to carried out should be clearly specified.
In algorithmic specifications, the instructions are
performed from top to button, unless the
instruction themselves otherwise specified.
11. Input and Output Definition
Inputs – are the data items that is presented in the
Outputs – are the data items presented to the
outside world as the result of the execution of a
program based on the algorithm.
An algorithm ought to produce at least one
output (otherwise, what use is it?...)
it consists of basic instructions that are realizable.
This means that the instructions can be
performed by using the given inputs in a finite
amount of time.
The instructions of an algorithm may order the
computer only to perform tasks that is capable of
13. Scope Definition
An algorithm applies to the following:
▪ Specific problem or class of problem
▪ The range of inputs has to be predefined
▪ The range determines the generality of the algorithm.
14. Algorithms can be expressed in many kinds of
16. “Pseudo” means imitation or false and “code”
refers to the instructions written in a
Pseudocode is another programming analysis
tool that is used for planning a program.
Pseudocode is also called Program Design
17. By wikipedia definition:
Pseudocode is a compact and informal
high-level description of a computer
programming algorithm that uses the
structural conventions of some
programming language, but is intended for
human reading rather than machine
18. Pseudocode is made up of the following logic
structures that have been proved to be
sufficient for writing any computer program:
19. It is used to perform instructions in a
sequence, that is one after another.
Thus, for sequence logic, pseudocode
instructions are written in an order in which
they are to be performed.
The logic flow of pseudocode is from top to
21. It is used for making decisions and for
selecting the proper path out of two or more
alternative paths in program logic.
It is also known as decision logic.
Selection logic is depicted as either an
IF...THEN or an IF...THEN...ELSE structure.
24. It is used to produce loops when one or more
instructions may be executed several times
depending on some of the conditions.
It uses structures called the DO_WHILE, FOR
and the REPEAT_UNTIL.
28. 1. Write only one statement per line.
Each statement in your pseudocode should
express just one action for the computer.
If the task list is properly drawn, then in
most cases each task will correspond to one
line of pseudocode.
30. 2. Capitalized initial keyword.
In the example above, READ and WRITE
are in caps.
There are just a few keywords we will use:
▪ READ, WRITE, IF, ELSE, ENDIF, WHILE,
ENDWHILE, REPEAT, UNTIL
31. 3. Indent to show hierarchy.
We will use a particular indentation pattern in
each of the design structures:
▪ SEQUENCE: keep statements that are “stacked” in
sequence all starting in the same column.
▪ SELECTION: indent the statements that fall inside the
selection structure, but not the keywords that form the
▪ LOOPING: indent the statements that fall inside the
loop, but not the keywords that form the loop
33. 4. End multi-line structures.
▫ All the initial keyword must always in line with the
last or end of the structure.
5. Keep statement language independent.
▫ Resist the urge to write in whatever language you
are most comfortable with. There may be special
features available in the language you plan to
eventually write the program in; if you are SURE it
will be written in that language, then you can use
the features. If not, then avoid using the special
34. In summary:
Write only one statement per line.
Capitalized initial keyword.
Indent to show hierarchy.
End multi-line structures.
Keep statement language independent.
35. • These are follows:
▫ Number each instruction.
This is to enforce the notion, “well-ordered collection of
▫ Each instruction should be unambiguous.
It means the computing agent, in this case the reader,
should be capable of carrying out the instructions. And
also, each instruction should be effectively computable
Nothing should be left out.
36. Following are some of the advantages of
Converting a pseudocode to a programming
language is much more easier than converting a
As compared to flowchart, it is easier to modify a
pseudocode of a program logic when program
modifications are necessary.
37. It also suffers from some of the limitations.
These limitations are as follows:
In the cases of pseudocode, a graphic
representation of program logic is not available.
There are no standard rules to follow for using a
pseudocode. Different programmers use their
own style of writing pseudocode and hence,
communication problem occurs due to lack of
38. To symbolize the arithmetic operators we use
Note: There is a precedence or hierarchy implied
in this symbols.
39. When we have to make a choice between
actions, we almost always base that choice
on a test.
There is a universally accepted set of symbols
used to represent these phrases:
43. It is more difficult to follow the
logic of or write pseudocode as
compared to flowcharting.