session1 - basic programming concepts

8/14/2019 Session1 - Basic Programming Concepts

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Basic Programming Concepts

Session 1


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Basic Programming Concepts / 2 of 23

Session Objectives Discuss algorithms

Draw flowcharts

List the symbols used in flowcharts

Discuss variables

List the different data types and make use of them in your own Cprograms

List and explain the different methods used for testing an algorithm

Test a program using dry run method Understand the structure of a sample C program

Identify the types of errors that can occur


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Basic Approach to Writing a

Program C# include

void main()

{

char name[15];

scanf(Enter name : %s, &name);

printf(Hello %S, name);

}

10 Input name$

20 Print Hello; name$30 END

BASIC

JAVAClass Hello

{public static void main(String args[])

{

String name;

System.in.readln(name);

System.out.println(hello + name);

}

}

Basic approach to programming

has remained the same inspite of

variations in languages. The

three codes perform the same

task.


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The Programming Approach to

Solving ProblemsClassroom

Leaving the

classroomHead towards

the staircase

Go to the

basement

Head for the

cafeteria

Cafeteria

Algorithm is a set of steps thatare performed to solve aproblem. The example belowdescribes an algorithm

These are the steps followed when a

student wants to go to the cafeteria

from the classroom.


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Solving a ProblemIn order to solve a problem

Understand the problem clearly

Gather the relevant information

Process the information

Arrive at the solution


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PseudocodeIt is not actual code. A method of algorithm - writing which uses

a standard set of words which makes it resemble code.

Each pseudocode starts with a BEGIN

To show some value , the word DISPLAY is used

The pseudocode finishes with an END

BEGIN

DISPLAY Hello World !

END


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FlowchartsIt is a graphical representation of an algorithm

START

DISPLAY Hello World !

STOP



The Flowchart SymbolStart or End of the program

Computational Steps

Input/Output Instructions

Decision making

& Branching

Flow Line

Connectors



Variables

Data

Memory

Each location in the memory is unique

Variables allow to provide a meaningful name for the location in memory

15

Data in memory

15



An Example

A, B and C are variables in the pseudocode

BEGIN

DISPlAY Enter 2 numbers

INPUT A, B

C = A + BDISPLAY C

END

Variable names takes away the need for a programmer to access

memory locations using their address

The operating system takes care of allocating space for the variables

To refer to the value in the memory space, we need to only use the variablename.



Guidelines to be followed while

Naming VariablesVariable names should begin with an alphabet

Proper names should be avoided while naming variables

The first character can be followed by alphanumeric characters

A variable name should be meaningful and descriptive

Confusing letters should be avoided

Some standard variable naming convention should be followed

while programming



Data Types

Datatype variableName

A data type describes the kind of data that will fit into a

variableThe name of the variable is preceded with the data type

For example, the data type int would precede the namevarName

int varName



booleanchardouble

Basic Data TypesThe basic data types are

floatint



Derived Data Types

intshortshort int

(Occupies less

memory placespace than int)

Derived data typeBasic Data

types

Data type

Modifiers

int unsigned int(Permits onlypositive numbers)

unsigned

int/doublelong/longdouble

(Occupies more

space than

int/double)

long


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Testing the AlgorithmThe three types of testing are

Dry Run

Independent

Inspection

Structured

Walkthrough


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Dry RunManual way of testing an algorithm for correctness

The values of the variables are tracked through every line of

the code

A table is first created, with as many number of columns as

the number of variables

The names of the variables are written in the column headers

The values of variables are noted down in the table at every stage

The final result is displayed at the end of the execution of the

code


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An Example of Dry RunStep 1. Start

Step 2. X = 10

Step 3. Y = 5

Step 4. M = 0

Step 5. M = X+Y+(X*Y)

Step 6. Y = Y+4

Step 7. M = M+Y

Step 8. Display X,Y,M

Step 9. End

X Y M

Initial values 10 5 0

After Step 5 10 5 65

After step 6 10 9 65

After step 7 10 9 74


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Independent InspectionAlgorithm is given to

Person 2

Person 1 Person 2 (not worked on the logic)

Returns the algorithm

to person 1 after using dry run

for testing


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Structured Walkthrough

Algorithm is

passed on

Person 1

Peers

The algorithm is accepted totally,

accepted after minor changes or

rejected totally

Peers will give

suggestions and

will suggest errors

or inefficiencies


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A Sample C Program# include

void main()

{int a, b,c;

printf(Enter the first number : );

scanf(%d, &a);

c=a+b;

}

printf(The sum of the numbers is %d, c);

Program working begins here

printf(Enter the second number : );

scanf(%d, &b);

Variables declared

Accepting input

Displaying number


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ErrorsAn error is a deviation of a program from the result required

The three types of errors are:

Logical errors

Syntax errors

Run time errors


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Other important programming

concepts I

Source CodeO/SCOMPILER

Object CodeSource Code

Compiler converts source code into object code, that is understood and

executed by O/S.


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Other important programming

concepts II

Source CodeO/SINTERPRETER

Each instruction in the source code is the interpreter and passed on to

the O/S , where it is executed.

session1 - basic programming concepts

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