Eng:Mona Ahmed Ali Abdullah 1
FLOWCHART
LAB(1)
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Introduction
• This section establishes the foundation for starting the
solution of simple problems by using a computer.
An algorithm could be defining as “a step-by-
step procedure for solving a given task”
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Introduction
• Notation of Algorithm:
An algorithm must satisfy the following criteria:
• Input: there is certain number (0 or more) of quantity which
are externally supplied.
• Output: at least one quantity is produced.
• Finiteness: for all cases the algorithm should terminate after
a finite number of steps.
• Definiteness: each instruction must be clear and
unambiguous to avoid any misinterpretation.
Ex: an operation such as “subtract 2 or 7 from 9” is not
permitted due to the ambiguity caused by it.
• Effectiveness: every instruction must be sufficiently basic,
that it can in principle be carried out by any person.
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Steps of Solving A problem
Solving a problem using a computer passes by
certain steps. These are known as steps or phases
of software development. These steps could be
given as follows:
Phase 1: problem definition.
Phase 2: problem analysis.
Phase 3: algorithm development.
Phase 4: program writing (program coding).
Phase 5: program transfer to the computer.
Phase 6: program testing and translation.
Phase 7: execution of program and output result.
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Algorithms and Programs
• An algorithm can be described in two ways: flowchart, and/or
pseudo-code.
1.Flowchart: represents a good, visible graph-wise way of
solving algorithms.
2.pseudo-code: a step-by-step procedure written using a
natural language in way that is very closed to programming
languages.
• It is also to be mentioned, that the computer program and the
algorithm are two different representations for the same thing.
The computer program is often defined to be “the expression of
an algorithm in a programming language.”
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Program Flowchart
Definition
Block diagram that uses predefined symbols and
interconnecting line to represent the logic and sequence of
specific program operation.
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Basic program flowcharting symbols
Terminal Processing
(start/end) (calculation and
storing
operation)
Input/output Decision
operation (conditional
branching)
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Basic program flowcharting symbols
Flow line
Subprogram
(direction)
call
connection
comment
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Types of Program Flowcharts
There are three types of program flowcharts:
Sequential flowchart
Branching (jump) flowchart.
Loop (repetition) flowchart.
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Types of Program Flowcharts
• What are Variables?
The variable is a container for a value that may vary
during the execution of the program.
• Variables and data types:
The data used in algorithms can be of different types. The
simplest types of data that an
algorithm might use are:
-numeric data, e.g., 12, 11.45, 901, etc.
-alphabetic or character data such as ‘A’, ‘Z’, or ‘This is
alphabetic’
-logical data, that is, propositions with true/false values
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Types of Program Flowcharts
• Naming of variables
One should always try to choose meaningful names for
variables in algorithms to improve the readability of the
algorithm or program. This is particularly important in
large and complex programs.
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The Sequential Flowchart:
• It is the simplest type of flowcharts, involving no decision
(i.e. no branches or loops).
• Fig 1 gives an example for this type of flowchart. When
such a program is executed, each statement will be
carried out respecting the order given by the flowchart.
The pseudo-code will be as follows
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The Sequential Flowchart:
• Start
Get the sum
Average = sum / 6
Output the average
Stop(end)
Fig 1: a sequential flowchart
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The Sequential Flowchart:
• Example 1:
Give a flowchart for finding the square value of a given number.
Solution:
At the beginning a value is entered to the numerical variable x.
The second step involves the
calculation of the square value of x, and assigning to another
variable y. the last step is to print
the values of x and y.
Steps:
Step 1: start(begin).
Step 2: input (enter or read) value of x.
Step 3: set y = x*x.
Step 4: output (print) values of x and y.
Step 5: end.
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The Sequential Flowchart:
,y
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The Sequential Flowchart:
• Example 2:
Give a flowchart for finding the summation of three
numbers.
Solution:
Steps:
Step 1: start.
Step 2: input (enter) values of x , y and z.
Step 3: set s = x + y + z .
Step 4: output (print) value of s.
Step 5: end.
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The Sequential Flowchart:
x,y,z
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The Sequential Flowchart:
• Example 3:
Give a flowchart for finding the solution of the following
equation y = 2x2 + 3z .
Solution:
Steps:
Step 1: start.
Step 2: input (enter or read) values of x and z.
Step 3: set y = 2*x*x + 3 * z .
Step 4: output (print) value of y.
Step 5: end.
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The Sequential Flowchart:
