A program is developed to solve our real-world problem. The program development process has mainly three phases: analysis, design and development. During the analysis phase, the detailed study of the problem must be done. After the analysis phase, the problem is designed by using different programming tools such as algorithms, pseudo codes, flowchart, etc. During this period, input, process and output of the problem are determined. The good program design makes efficient and faster development of program. After designing, it is ready for development i.e. programming the problem.
i.
Algorithm
Algorithm is one of the most basic tools used
for solving problem. It is defined as the finite sequence of instructions for
solving a problem. It consists of stepwise list of English statements making
sequential procedure. The number of instructions should be minimized to
increase the speed of the algorithm.
Algorithm is a finite sequence of instructions for solving a
problem.
There are not any specific rules for designing
algorithms however, designing an algorithm requires a clear understanding of a
problem. Before writing an algorithm, a designer should have knowledge about
the input, output and process of a problem. The instructions are written in
simple informal English statements. Some of the major guidelines while writing
an algorithm are as follows:
·
The number of instructions should be finite.
·
Each instruction should be in simple language and no ambiguous
instructions should be included.
·
It should have an input, process and desire output after
executing the algorithm.
·
It should not depend on any language or computer.
Algorithm for calculating simple interest
Step
1: Start
Step 2: Input Principal, Rate and Time
Step 3: Multiply Principal , Rate and Time and
Divide by 100
Step 4: Store the result in Simple Interest
Step 5: Output Simple Interest
Step 6: Stop
Advantages of algorithm:
·
It is simple and easy to understand.
·
It has no hard and fast rules for writing an algorithm.
·
It does not require prior knowledge of programming during
writing algorithms.
Disadvantages of algorithm:
·
It is more difficult to translate algorithms into program
codes.
·
It is not considered as a standard tool for program designing.
ii.
Flowchart
When an algorithm is expressed in pictorial
form, then it is called flowchart. It is defined as a pictorial representation
of an algorithm that describes the procedure to solve a problem. lt shows the
order of instructions and relationship between them. The purpose of
constructing flowchart is to help for the programmer for understanding the
logic of a problem.
Flowchart is a pictorial form of an algorithm. It uses meaningful
symbols to represent different types of instructions.
It uses different meaningful symbols to solve
a problem. It is useful tools when an algorithm is short and fits conveniently
on one page. Moreover, it also helps for the solutions of mathematical and
logical problems. It defines the sequence and the flow of operations of a
problem. It clearly explains the input, process and output of a problem. It
shows the internal relationship between the instructions. Some of the major
features are as follows.
·
It is only suitable for small logical or mathematical problems.
·
It cannot solve complex and lengthy problems.
·
It can only solve procedural types of problems.
·
Designers should have knowledge about the symbols of flowchart.
Symbols used in Flowchart
Flowchart for calculating Simple Interest
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Flowchart
to calculate simple interest |
Advantages of Flowchart
·
It is very efficient tool for solving logical and mathematical
problems.
·
It shows the types of instruction whether; an instruction is
input/output, process or logical.
·
It is easy for converting flowchart into program codes.
·
It is easy for testing and maintenance.
Disadvantages of Flowchart
·
It is difficult for solving large and complex problem.
·
It is time consuming for designing a flowchart.
·
It is difficult for modifying and updating the flowchart.
·
Designer should be familiar with different symbols and their
respective meanings.
iii.
Pseudo Code
Pseudo code is a kind of algorithm for
solving a problem. The instructions of pseudo code are written by using English
phrase and mathematical expressions. It is also known as structured English. It
has no specific rules for writing instructions, but the instructions are very
closer to high level language instructions. Designer should have basic
knowledge about high level language instructions before writing pseudo code. It
is independent of any programming languages.
Pseudo code is a kind of algorithm in which the instructions are
expresses in more English like structure and mathematical expression. The
instructions of pseudo code are similar to the program instructions.
Pseudo Codes for calculating simple interest
Start
Input P,T and R
Calculate SI=(P*T*R)/100
Output SI
Stop
Advantages of Pseudo Code:
·
Complex and lengthy problems can be easily solved by using
pseudo code.
·
It is easy for converting pseudo code into program codes.
·
It is easy for testing because it can be tested by using
computer aided tools.
·
It is independent of any programming languages.
Disadvantages of Pseudo Code:
·
Designer should have prior knowledge of programming while
writing pseudo code.
·
It is more complex than algorithm.
CONTROL STRUCTURE
A control structure is the most powerful tool
in any high level language which is used to control the flow of instructions in
a program. Moreover, it is used to develop program logic for the solution of a
problem. It is also known as control statement. The main components of control
structure are sequence, selection and repetition / iteration / looping.
A control structure is major component of a high level language
that helps to control the flow of instructions in a program.
i.
Sequence
A sequential control structure is a linear
structure. It executes statements one after another in a sequence. There is no
mechanism for choosing alternate paths in statements flow. It executes one
statement then automatically moves to next statement and so on.
Algorithm Syntax of Sequence:
Start
Statement 1
Statement 2
..................
..................
Statement N
End
Flowchart of Sequence:
Example of Sequential Control
Structure
Write an algorithm and a flowchart to
calculate area of rectangle.
Algorithm to calculate area of rectangle
Step 1: Start
Step 2: Input L,B
Step 3: Calculate A=L*B
Step 4: Output A
Step 5: Stop
Flowchart to calculate area of rectangle
Ch 5 Assignment 3
1.
What are the three states of program development?
2.
List any three program design tools.
3.
Write an algorithm to calculate area of square.
4.
Write an algorithm to calculate area of a circle.
5.
Write an algorithm and a flowchart to calculate to calculate
simple interest.
ii.
Selection
A selection structure is known as branching
statement. It has the decision-making capabilities based on given conditions.
It allows alternative paths for the instructions of a program based on given
conditions. If the condition is true, one set of instructions will be executed
otherwise, another set of instructions will be executed. Mainly, there four
categories of selection structures such as if else, if else if, nested if else
and switch case structure. Let us discuss simple if else structure here and we will
be discussed the other categories of selection structures later in C
programming.
Simple if else structure is the basic type of
selection structure. If a given problem has one condition with respective two
actions: true/false, then we can use simple if else structure. We should
consider either true or false part. If the given condition is true, then the
statement 1 will be executed, otherwise the control moves to else part i.e.
statement 2 will be executed. In this case, the else part is optional so, if we
remove else part then it will become simple if statement.
Algorithm syntax of if else
if(condition)
statement 1;
else
statement 2;
Simple if statement
if(condition)
statement
Flowchart of if else statement
Example of Selection Control Structure
Write an algorithm and a flowchart to find the
greater number among two numbers.
Algorithm to find the greater number among two numbers
Step
1: Start
Step 2: Input A,B
Step 3: if(A>B)
Output A is greater.
else
Output B is greater.
Step 4: Stop
Flowchart to find the greatest number among two numbers
Ch 5 Assignment 4
1.
What are the three major components of selection structure?
2.
List four types of selection structures.
3.
Write an algorithm and a flowchart to check the number is
positive or negative.
4.
Write an algorithm and a flowchart to check the number is odd or
even.
5.
Write an algorithm and a flowchart to check the number is
divisible by 5.
iii.
Iteration / Looping
Iteration is commonly known as looping or
repetition. In iteration process, an instruction or group of instructions is
repetedly executed until some condition has been satisfied. Every loop has
three fundamental components: intilialization, condition and counter. An
intialization statement defines the starting point of the loop. The condition
defines the stopping point of the loop and finally the counter counts the
number of iterations. The increment and decrement operations are used as
counter. If the condition of a loop is always true, then the loop will be
executed infinite times and such loop is called infinite loop. There are three
types of loops: while, do while and for loop.
Let us consider simple while loop. In this
loop, computer first checks the condition, if the condition is true, then it
executes the statements inside loop. The process is repeated and the value of
increment or decrement operator is also changing. When the condition is false
the loop stops. If the given condition is intially false, then the loop will
not execute further.
Algorithmic Syntax of
while loop
intialization;
while(condition)
{
statements
..........
..........
increment/decrement;
}
Flowchart of while loop
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Flowchart
of while loop |
Example of Looping | Iteration
Control Structure
Write an algorithm and a flowchart to print 1
to 10.
Algorithm to print 1 to 10
Step
1: Start
Step 2: i=1
Step 3: while(i<=10)
{
Output i
i++
}
Step 4: Stop
Flowchart to print 1 to 10
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Flowchart
to print 1 to 10 |
ABSOLUTE BINARY,
ASCII, BCD
A computer understands only binary numbers in
the form of two electronic states: high voltage(1) and low voltage (0). Such
binary notations are further derived into different standard codes. Such codes
are used to represent the data for convenience to the users. Different data
representation codes are used in computer system. Some of the popular codes are
as Absolute Binary, BCD, ASCII, EBCDIC, Unicode etc.
Absolute Binary
We use plus sign + and minus - sign to
represent positive and negative numbers respectively. In computer system, such
mechanism is not employed. In absolute binary method, 0 is placed before the
binary number to represent positive number and 1 is placed before the binary
number to represent negative number. The binary number is expresses in
8-bits,16-bits,32-bits or 64-bits format on the basis of word length of
processor. The most significant bit denotes the sign bit and the rest of the
bits represent the actual number. For examples: To represent +12, in 8 bit absolute
binary number is 00001100, similarly for -12, the absolute 8 bits binary
number is 10001100.
BCD
The binary coded decimal code is used to
represent numeric data in computer. It uses 4 bits to represent a single digit
decimal number. For examples: BCD code for 7 is (0111) and BCD code for 15 is (0001
0101).
ASCII
The American Standard Code for Information
Interchange is the standard code to represent data in computer. It assigns
numeric value for each character, number and symbol. It is extensively used in
most of the computers, peripherals and soft wares. It is 8-bits code which
represents 256 characters or symbols. For examples: ASCII code for
A-65,B-66,C-67,a-97,b-98 etc.
EBCDIC
It stands for Extended Binary Coded Decimal
Interchange Code. It is an eight bits code, which defined 256 different
characters or symbols. It is mostly used in IBM mainframe and other
minicomputers. It is not used in personal computer.
Unicode
Unicode Worldwide Character Standard is a
character set which provides 16 bits codes to represent 65536 different
character, numbers, symbols etc. It includes characters of all the languages of
the world. It also includes all characters from ASCII character set. A newer
version of Unicode has 32 bits character set which represents more than 4
billion different character or symbols from the world.
Ch5 Assignment 5
1.
What are the three components of a loop?
2.
What happens when the condition is always true in the loop?
3.
Write an algorithm and a flowchart to print 100,99,98,...1.
4.
Write an algorithm and a flowchart to print
1 3 5 .....N
5.
Write an algorithm and a flowchart to display multiplication
table of 5.
6.
Write the full form of BCD, ASCII, EBCDIC and Unicode.
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