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Lecture NoteWEEK 1

Designing Solution to Computer Based

Problem

School of Computer Science & IT, DAVV Indore

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Algorithm

An algorithm is a well-developed, organized approach to solving aAn algorithm is a well-developed, organized approach to solving a

complex problem.complex problem.

Developing an AlgorithmDeveloping an Algorithm

1.Identify the Inputs1.Identify the Inputs

2.Identify the Processes2.Identify the Processes

3.Identify the Outputs3.Identify the Outputs

1.2 An algorithm must have following properties

There must be no ambiguity in any instruction.

There should not be any doubt about which instruction is to be executed next.

The description of the algorithm must be finite.

The execution of the algorithm should conclude after a finite number of steps.

After performing the instruction that is after the algorithm terminates the desiredresult.

1.3 Three methods used for creating an algorithm

Steeping

Looping

Choosing

Steeping

This is where all the instructions needed to solve our problem are set out one after to

another. Here is an example

Example: Write an Algorithm of Addition of two numbers

STEP 1: START

STEP 2:READ VALUE OF FIRST NUMBER AND SECOND NUMBERSTEP3: CALCULATE ADDITION OF FIRST NUMBER AND SECOND

NUMBER:

SUM=FIRST NUMBER+SECOND NUMBERSTEP 4:DISPLAY SUM

STEP 5: STOP

Example: Write an Algorithm of simple interest (SI=P*R*T/100)

STEP 1: START


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STEP 2:READ VALUE OF P, R AND T

STEP3: CALCULATE SIMPLE INTREST BY USING FORMULA:SI=P*R*T/100

STEP 4:DISPLAY SIMPLE INTREST

STEP 5: STOP

Looping

Repeat an instruction or a set of instructions a number of times. In this case use loops

TheRepeat untilloop

The While loop

TheForloop

TheRepeat untilloop

This type of loop keeps carrying out a command a command UNTIL a given

condition is satisfied. The condition is given with the UNTIL command. Here is anexample

Example: Write an Algorithm to print five times Hello.

STEP 1: START

STEP 2: INITILIZE NUM TO 1

STEP3: REPEATSTEP 4: PRINT HELLO

STEP 5: UNTIL THE NUM IS NOT FIVE

STEP 6: STOP

The While loop

In this type of loop the condition is given along with the WHILE command and end

with END WHILE command. Here is an example

Example: Write an Algorithm to print table of 2.

STEP 1: STARTSTEP 2: INITILIZE NUM TO 1

STEP 3: WHILE NUM IS LESS THAN 10STEP 4: MULTIPLAY THE NUM BY 2

STEP 5: DISPLAY TABLE HAS 2STEP 6: END WHILE

STEP 6: STOP

The Forloop


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TheForloop number of times it is repeated .the command to be repeated between

FOR and END FOR. Here is an example

Example: Write an Algorithm to print number from 10 to 20.

STEP 1: START

STEP 2: FOR NUMBER=10 TO 20

STEP 3: PRINT NUMBER

STEP 4: END FORSTEP 5: STOP

Choosing

This method is used to take decision. This technique is called choosing, and uses

the commands IF, THEN and ELSE.This type of command a condition is given in the IF command followed by an action to

be taken. If the condition if satisfied follow it by THEN command. Here is an example

Example: Write an Algorithm to decide weather or not go to school

STEP 1: STARTSTEP 2: IF IT IS WEEKDAY AND IT IS NOT A HOLYDAY

STEP 3: THEN GO TO SCHOOL

STEP 4: ELSE STAY AT HOME

STEP 5: STOP


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Lecture Note

WEEK 2


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1. Flowchart

Flowchart is a pictorial representation of an algorithm in which the steps are drawn in the

form of different shapes of boxes and the logical flow is indicated by interconnectingarrow.The boxes represent operations and the arrows represent the sequence in which the

operations are implemented.The main purpose of the flowchart is to help to understanding the logic of the program.

2.1 Guidelines for Drawing a Flowchart

The following are some guidelines in flowcharting:

a. In drawing a proper flowchart, all necessary requirements should be listed out inlogical order.

b. The flowchart should be clear, neat and easy to follow. There should not be anyroom for ambiguity in understanding the flowchart.

c. The usual direction of the flow of a procedure or system is from left to right or

top to bottom.d. Only one flow line should come out from a process symbol.

e. Only one flow line should enter a decision symbol, but two or three flow lines,

one for each possible answer, should leave the decision symbol.f. Only one flow line is used in conjunction with terminal symbol

g. If the flowchart becomes complex, it is better to use connector symbols to reduce

the number of flow lines. Avoid the intersection of flow lines if you want to makeit more effective and better way of communication.h. Ensure that the flowchart has a logicalstartandfinish.

i. It is useful to test the validity of the flowchart by passing through it with a simple

test data.

2.2 Importance of Flowchart

A flowchart helps to clarify how things are currently working and how they could beimproved.

1. Communication: Flowcharts are better way of communicating the logic of asystem to all concerned.

2. Effective analysis: With the help of flowchart, problem can be analyzed in moreeffective way.

3. Proper documentation: Program flowcharts serve as a good program

documentation, which is needed for various purposes.

4. Efficient Coding: The flowcharts act as a guide or blueprint during the systemsanalysis and program development phase.


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5. Proper Debugging: The flowchart helps in debugging process.

6. Efficient Program Maintenance: The maintenance of operating program becomeseasy with the help of flowchart. It helps the programmer to put efforts more

efficiently on that part

2.3 Symbols used in flowchart

Flowcharts use special symbol shapes to represent different types of actions or steps ina process. Lines and arrows show the sequence of the steps, and the relationships amongthem.

2.4 Flowchart structure

1. Sequence: A sequence process is a series of processes carried out one afterthe other. Where information can flow in a straight line.


(Flow Line): Flow lines are used to connect symbols. These lines indicatesequence of steps and the direction of flow.

(Terminal): This symbol is used to represent the beginning (start), the

termination (end) or halt (pause) in the program logic.

(Input/Output): It represents information entering or leaving the system,such as customer order (Input) and serving (Output)

(Processing): Process symbol is used for representing arithmetic and datamovement instruction.

(Decision): Decision symbol denote a decision to be made .the programshould continue along one of the two routes (IF/ELSE).this symbol has one

entry and two exit paths. The path chosen depends on whether the answer toa question is yes or no.

(Connector): Connector symbol is used to join different parts of program.

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2. Selection (branches): Where the decisions are made according to some predefined condition. The If_Else_If processes logically complete the binary

decision block by providing two separate processes. One of the processes will becarried out in the each path of binary decision.

The flow chart of the if statement:


Example: Find average of fivenumbers

Example: convert Celsius toFahrenheit

F=1.8*C+32

Start

Input T (in C)

End

Display F

Avg=(a+b+c+d+e)/5

Start

Read value a,b,c,d,e

End

Display Avg

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The flow chart of the ifelse statement:

The flow chart of the switch statement:


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Example:program to find the greatest number of three numbers.

3. Repetition: Where the logic can repeat in a loop, that is, where a sequence ofsteps is repeated until the desired output is obtained. The while process allow for

the representation of a conditional loop structure within a program.

Flow chart of the while loop:

Flow chart of the for loop:


NO

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Example: Draw a flowchart to find the sum of first 50 natural numbers

Example: Draw a flowchart to find the sum 20 even numbers natural numbers


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2.5 Limitation of flowchart

Complex: The major disadvantage in using flowchart is that when a program isvery large, the flowchart may continue foe many pages, marking them hard to

follow. Flowchart tends to get large very quickly and it is difficult to follow the

represented process.

Costly: Drawing simple flowcharts may be a cost effective process. However, ifthe flowchart is to be drawn for a huge program, the time and cost factor of

program development gets out of proportion, making it a costly affair.

Difficult to modify: Modification to a flowchart usually requires redrawingthe entire logic again, and redrawing a complex flowchart is not a play. It is easyto draw thousands of flow lines and symbols along with proper spacing,

especially for a large complex program.


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Lecture Note

WEEK 3

Computer Programming Languages


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Types of Computer Programming Language

1. Machine language

2. Assembly language

3. High-level languages

Machine language programs were made up of instructions written in binarycode.

This is the native language of the computer.

Each instruction had two parts: Operation code, Operand Operation code (Opcode): The command part of a

computer instruction.

Operand: The address of a specific location in thecomputers memory.

Hardware dependent: Could be performed by only one type of computer with a

particular CPU

Assembly language programs are made up of instructions written in mnemonics. Mnemonics: Uses convenient alphabetic abbreviations to

represent operation codes, and abstract symbols to represent operands. Each instruction had two parts: Operation code, Operand

Hardware dependent.

Because programs are not written in 1s and 0s, thecomputer must first translate the program before it can be executed.

High-level languages: Use statements that resemble English phrases combinedwith mathematical terms needed to express the problem or task being programmed.

Transportable: NOT-Hardware dependent. Because programs are not written in 1s and 0s, the computer must

first translate the program before it can be executed.


READ num1

READ num2LOAD num1

ADD num2

STORE sum

PRINT sum

STOP

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Assembled, Compiled, or Interpreted Languages

All programs must be translated before their instructions can be executed.

Computer languages can be grouped according to which translation process is used to

convert the instructions into binary code:

Assemblers Interpreters

Compilers

Assembled languages:

Assembler: a program used to translate Assembly language programs.

Produces one line of binary code per original program statement. The entire program is assembled before the program is sent to the

computer for execution.

Interpreted Languages:

Interpreter: A program used to translate high-level programs.

Translates one line of the program into binary code at a time:

An instruction is fetched from the original source code. The Interpreter checks the single instruction for errors. (If an error

is found, translation and execution ceases. Otherwise)

The instruction is translated into binary code. The binary coded instruction is executed.

The fetch and execute process repeats for the entire program.

Compiled languages:

Compiler: a program used to translate high-level programs. Translates the entire program into binary code before anything is sent to

the CPU for execution. The translation process for a compiled program:

First, the Compiler checks the entire program for syntax errors in the

original source code. Next, it translates all of the instructions into binary code.

Two versions of the same program exist: the original source code version,

and the binary code version (object code). Last, the CPU attempts execution only after the programmer requests that

the program be executed.


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