Importance of the Decision Table

Importance of the Decision Table
1. This is more modular. Statisticians can use this table for
programming especially in database.
2. Tables are always attractive. Written information in decision table
format is always helpful in decision making.
3. This is easier to programme. Programmers can code the problem in
any programming language from decision table. So decision table is
used by system analyst.
4. The operating principle of a machine can be represented by decision
table, so users can take help from it.

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What is a Decision Table

hWhat is a Decision Table?
Decision table is the tabular or graphical representation of problem
solving method. So this is more precise than other method of problem
solving like pseudocode. Different decisions are taken according to
different conditions. Decision table must have the scope of representing
the conditions. There are different rules which states one or more actions
to be done for satisfying one or more conditions. Thus decision table can
be said a tabular representation of the program.

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Use of Pseudocodes

    Use of Pseudocodes
1. Pseudocode is a structured language. It can be easily used for
algorithm writing. Pseudocode is understandable to class of educated
people. This can be used as communication media of computer
people and its users.
2. This is used for communicating process specifications that shape
program design. This is actually the primary design or draft design of
programs.




3. Users can easily understand the program. So the operating principle
or procedure can be easily expressed by pseudocodes. Pseudocodes
are also used in documenting the program.
4. Different scientific problems solvable by computers are written in
Pseudocodes. These are given in several books whenever needed.

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Structure of Pseudocodes

 Structure of Pseudocodes
Pseudocode uses some logic patterns as the basic control structures of
structured programming.
These are: Sequence structure
The sequence structure is single steps or actions that follow one another
without interruption. The series of actions does not depend on the
existence of any condition. The pseudocode for the sentence structure is:
Do action1
Do action2.
For example:
Read customer bill
Print customer bill.
Decision structure
The decision structure, where two or more actions can be taken
depending on which satisfies a stated condition. The pseudocode format
for decision structure is :
An advantage of pseudocode is
that system builders can
concentrate on processing logic
independent of syntax
guidelines of any programming
language.
Programming Tools
25
In C language
if (expression)
statement 1
else
statement 2




For example :
if (Income >Tk. 1,000)
income_tax=4*Income;
else
income_tax=0;
Printf(“%f”, income_tax);
In Pascal
IF (condition 1 in true)
Do X
ELSE
DO Y
ENDIF
For example :
IF (Income >Tk. 10,000)
income_tax=4*Income
ELSE
income_tax=0
ENDIF

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Definition of Pseudocodes

Definition of Pseudocodes
Pseudocode, sometimes called structured English, is a method of
expressing programme logic using plain English statements rather than a
programming language. It uses narrative statements rather than graphic
symbols such as trees of tables to describe a procedure. An advantage of
pseudocode is that system builders can concentrate on developing
processing logic independent of syntax guidelines of any programming
language. Syntax guideline is the rules of formulating instructions.
Pseudocode can be easily translated into a programming language.

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Modularity in Flowchart

 Modularity in Flowchart
Some times the same job may be repeated in different places in
flowchart. In every place of flowchart same sequence of actions are
included every time. This enlarges the flowchart and makes it unusually
big. It is difficult to understand such flowchart. So another flowchart is
used separately for this repetitive module. This is exactly like our
traditional flowchart described so far. The only difference is the calling
symbol, defined as Fig. 4.6 and said to be modularity in flow chart.
For example we can consider the dialling process as a submodule. So the
flowchart for visiting botanical garden can be modified as shown in Fig

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Examples of Looping

Examples of Looping

Suppose you wish to visit the botanical garden, and therefore, are
looking for one of your friends to accompany you. So you take out your
book of few phones and select a likely prospect. Dial the number, make
few talk, and finally invite the friend to visit. If he (or she) accepts the
offer, you have finished your work. If you are refused, then go back and
select another number. These actions are shown in a flow chart in Figure
 The essential concept in this algorithm is the branch back to an

earlier statement to create a loop. A loop is a sequence of instructions

which is repeated several times. Note that each time the programme goes

through the loop a different telephone number is used; the instructions

remain unchanged but the data operated on differs. If you eventually get

an acceptance, you would reach the end block. However, if you keep on

getting rejections, then you re-execute the loop instructions. Since you

only have a finite number of telephone numbers in your book, you must

stop when the data run out.

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Looping in Flowchart

Looping in Flowchart

Computers are efficient in executing repetitive operations. In programs,

there are invariably repetitive operations, which are needed to be

represented in flowcharts. Consider the following flowchart where the

start block shows where the algorithm begins.

In figure 4.1 an unconditional infinite loop is shown. The exception in

this flowchart is the flow direction from lower to upper. The last block of

this flowchart will never be executed.

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Some Symbols of Flow Chart

 Some Symbols of Flow Chart
Normally, we begin from step 0 and go to the next statement and finished
at the space end unless directed to do otherwise by a GO TO instruction
as in steps 3, 6, 9, 11 and 12 in the present example. Notice that this
algorithm, like the previous one, contains an IF statement. IF statements
permit jumping around and skipping some instructions. GO TO and IF
statements cause a program to branch- that is, to make an out-ofsequence
jump from one statement to another.

It is difficult to follow the branches; so in order to make the logic of the
algorithm clearer; it is useful to represent the algorithm as a flowchart
since visual representations are more effective for us. Before converting
the algorithm for getting to college, let us introduce the symbols that are
used to represent different actions in a flowchart. The symbols of the
flowcharts are standard.

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Definition of Pseudocodes

10. Definition of Pseudocodes Pseudocode, sometimes called structured English, is a method of expressing programme logic using plain English statements rather than a programming language. It uses narrative statements rather than graphic symbols such as trees of tables to describe a procedure. An advantage of pseudocode is that system builders can concentrate on developing processing logic independent of syntax guidelines of any programming language. Syntax guideline is the rules of formulating instructions. Pseudocode can be easily translated into a programming language.

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Flow Chart for Describing Algorithms

9. Flow Chart for Describing Algorithms An algorithm is a set of instructions which when followed will produce the solution to a given problem. Algorithms occur in noncomputing contexts as well as in programming. You can think of the recipe for baking a cake as an algorithm- certainly a recipe is a set of instructions which, when followed, will result in a cake. Likewise, the instructions in a stereo kit are steps which, when followed, will produce a properly assembled electronic device. If the instructions are poorly written or if they are not followed precisely, the result is a soggy cake. Consider the following instructions that you need to make a cup of tea. 1. Pour water in a kettle. 2. Turn the oven on. 3. Place the kettle on the oven. 4. Turn the oven off.

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Writing or Expressing Algorithm

8. Writing or Expressing Algorithm Pseudocode or structured English is suitable for expressing an algorithm. Here, unlike natural languages, each statement has an unambiguous meaning. Generally algorithm is expressed in any high level language 8.1 Analysis of Algorithm Whenever you design an algorithm you must analyse it. You have to determine the cost of algorithm. If the cost is less than the exisiting algorithm, this algorithm will be implementable. Generally the cost of multiplication, addition and data transfer is calculated. If the cost of a new algorithm is of lower order than previous one then we are assured that the algorithm will give better results. Let us begin to implement the algorithm in a program. Example: There are three numbers. You have to find their median. Write the algorithm in structured English. Consider a, b, c are numbers. if b  a  c then median  a else if a  b  c then median  b else median  c endif.

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Use of Algorithm in Programming

Use of Algorithm in Programming

Whenever a problem is found the method of solving it should be written

in an easier way. This is called an algorithm. The step of algorithm is

converted to any programming language. A lot of intelligences is

required to design an algorithm. Programming means translation of an

algorithm into a programming language. The study of algorithms

includes many important and active areas of research. Some of these are

follows in the next subsection.

How to Design an Algorithm
Designing new algorithms means finding new methods of solving
problems. This is done by mathematicians or computer scientists
sometimes with the help of existing algorithms. Sometimes they are
developed by changing the steps which improves the computational
requirements. There are several fields where algorithms can be designed.
These are sorting, searching, linear programming, pattern recognition,
artificial intelligence etc. To design efficient algorithms clear theoretical
background on these topics is necessary. Only programming knowledge
is not sufficient for this purpose.

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Definition and Properties of Algorithm

14. Definition and Properties of Algorithm In Webster's dictionary, the word "Algorithm" is defined as "any special method of solving a certain kind of problem". But in computer science it has a special meaning. It means a step by step procedure for solving a problem by a computer. An algorithm has following properties. 1. An algorithm must be composed of a finite number of steps. Each step may be another algorithm composed of several steps. 2. Each step of the algorithm must be definite. The meaning of the operation must be clear. We cannot have an operation like "add 2 or 3 to x" in an algorithm. 3. The steps must be effective; each step can at least in principle be done by a person using pencil and paper in finite amount of time. Performing arithmetic on integers is an example of an effective operation, but arithmetic with real numbers is not necessarily effective, since some values may be expressible only by an infinitely long decimal expression 4. The algorithm may have one or more inputs but it must have at least one output. 5. An algorithm must terminate after a finite number of operations. There is another word for an algorithm which obeys all of the above properties except termination, and that is computational procedure. An operating system of a digital computer is an example of a computational procedure since it does not terminate, but continues in

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Development of programming languages

10. Scientific research Scientific research requires computers for implementing the theory into practice. Huge numbers of calculations are required for this purpose. Only a computer program can help the scientists out. There are some programs which are useful for scientific calculations. For example, FORTRAN, C++, Mathematica, Math Lab. Simulation is also very necessary for research, which can be performed using simulation packages. 11. Development of programming languages This is one of the main purposes of programming. High level languages are made from low level languages. Even top versions of high level languages are programmed by low version of high level languages. This idea of developing programming tool is called boot strapping. That is the objective of programming is to make the programs easier so that a layman can run his machine without the help of a programmer. This is actually the future trend of programming. Now the programmers are not concerned about the data structures and algorithms used. The compiler will use the proper data structure and efficient algorithm to solve the problem. 12. Object of this programming course This course of programming is not all in all in computer programming. We have discussed some aspects of high level languages and then discussion on Pascal programming language will be found in subsequent.

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Developing the system

8. Developing the system Demand increases day by day. So new systems should be introduced. This is done by introducing new programs and new versions of programs. Sometimes new machines come up with extra facilities. Existing systems may not support these facilities. At that time developed programs are necessary for better utilisation of machines. 9.Scientific research Scientific research requires computers for implementing the theory into practice. Huge numbers of calculations are required for this purpose. Only a computer program can help the scientists out. There are some programs which are useful for scientific calculations. For example, FORTRAN, C++, Mathematica, Math Lab. Simulation is also very necessary for research, which can be performed using simulation packages.

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Purpose of Programming

5. Fourth Generation Languages Scientists are trying to develop computer languages like human languages. They have not been successful but may be successful in near future. These languages have greater built-in facility such as database query, searching, sorting and interfacing. FoxPro, Cobol, Visual Basic, MS Access, Oracle Forms and Reports, SQL systems make use of such programs or languages. These are also known as the Fourth Generation Languages (4GL). 6. Purpose of Programming There are several purposes of programming. These are discussed below. 7. Computer program for automated systems Different offices need different system. So a ready made software is not enough for this purpose. Special programs should be written for office automation. These softwares may be used for accounting, payroll systems, machine control, industrial control, billing system of electricity, telephone and water, result processing of examination etc. It is important to develop these softwares properly because the output of the whole system depends on the output of the computer system. C++, Mathematica, Math Lab. etc.. Visual Basic, SQL, ORACLE. Result Processing.

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Principles of Programming

3. Different Types of Language Low level languages In old days computers were very large and were not much reliable. Programming was done by switches and there was no facility to use the program. This approach of computer programming was completely a hardware technology. Next the approach of machine language comes up. In this approach instruction set of the computer consists of some numerical digits. This instruction set is used to build up a program. This code is difficult to understand for human beings. Next assembly language was introduced. In assembly language the numerical codes are replaced by suitable names which are understandable. This has made programming easier. 4. High level languages This type of languages are like English language. But this is more structured. Actually this type of languages support mathematical notations used in arithmetic expressions. There are some special rules for writing programs in high level languages. Pascal, C, C++, Mathematica, Java, Math lab etc. Ada are all high level languages. High level languages are easy to write, compile and suitable for error correction.

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COMPUTER PROGRAMMING

 Definition of Programming
Programming is writing instructions for a machine specially a computer.
The machine which works differently according to the instructions given
to it is called a programmable machine. The jobs of these machines are
not fixed. We can change the working plan of the machine by changing
the instructions or programs. Computers are machines that can
understand the instruction and work properly according to the
instructions given.
In short, programming means step by step instructions for solving a
problem by computer.

What is a Language?
The instruction given to the computer must have a particular format.
Computers are unable to understand human language. There are several
levels of format or language which a computer can understand. The
interest of understanding computer languages increases day by day.
History of computer languages is as old as computer science. This is
described in the following sections.

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