Introduction to Programming Enter Created by N. Nembhard.

Introduction to Programming

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Created by N. Nembhard

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What is a Computer Program?

Basic Elements of Any Program

The Main Steps in Developing a Program

Basic Control Structures

Types of Errors

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Pseudocode

Pseudocode consists of English like statements that describe the processing steps of a program in paragraph form. It is an informal language that is easy and user friendly to use. It is not an actual programming language and are not executed on computers. They can help you “think out” a program before attempting to write it in a programming language.

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HomeAlgorithms

A computer is only a tool that can do what it is specifically told to do. We can direct the computer to do what we want by specifying our needs in a discrete step-by-step manner.

An algorithm must be developed, which is a step-by-step procedure to solve a problem.

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An algorithm must meet the following requirements:– Use operations from only a given set of basic

operations– Produce the problem solution, or answer, in

a finite number of such operations.

AlgorithmsHome

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High Level Languages

There are many programming languages –some examples are Basic, c, c++, Visual Basic, Java, Pascal. These are high level languages which are closer to human languages. Programs can also be written in low level languages such as assembly language and is closer to the language of the computer.

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What is a computer Program?

A program is an organized list of instructions that when executed causes the computer to behave in a predetermined manner. It is a step-by-step list of instructions written in a particular computer programming language.

Without programs, computers are useless.


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Main Steps in Developing a Program

1. Define the problem

2. Outline the solution

3. Develop the outline into an algorithm

4. Test the algorithm for correctness

5. Code the algorithm into a specific

programming language

6. Run the program on the computer

7. Document and maintain

the program


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The Basic Elements of any Program

Input

Processing

Output

The basic elements of any program are:


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Input

This is entering or sending data to the computer. The most frequent way of entering data is by using the keyboard.


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Processing

The processor or microprocessor is the part of the computer that reads, interprets and executes the program instructions. Processors are integrated circuits that contain transistors and other electronic components. It is a small chip that functions as the “brain” of the computer. The processor is also called the Central Processing Unit (C.P.U)


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Output

Sending or displaying data to the user. Common output devices includes the monitor and the printer.


What Have You Learnt?

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QuizClick on the correct answer:

A set of English like statements that is used as an informal language is called:

Algorithm

Psuedocode

Computer program

A

B

C

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Which of the following is NOT a high level language?

Basic

Assembly

C++

A

B

C



The basic elements of any program are:

Input, storing, processing

Input, storing,output

Input, processing, output

A

C

B



QuizIs the following statement true or false?

Click on true if the statement is correct or false if it is incorrect.

A computer program is a step-by-step list of instructions written in a particular computer programming language.


True FalseCreated by N. Nembhard

End of Quiz!



Errors that programmers usually make includes:

Semantic Errors

Syntax Errors

Logic Errors

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Types of Errors


Semantic Errors

This is where meaning of the language is not obeyed. For example, what the words really say or what functions are requested in the command.



Syntax ErrorsViolations of the language. Syntax error refers to the spelling and grammar of a programming language. The particular programming language used expects words entered in a specific form. The expected form is called the syntax.

Each program defines its own syntactical rules that control which words the computer understands, which combinations of words are meaningful and what punctuation is necessary.



Logic Errors

A logic error occurs when a step in the program logic is incorrect e.g. an average program will produce a wrong answer if the sum of the numbers is divided by a number other than the total count of the numbers.



Basic Control StructuresThe basic control structures are:

Simple Sequence

If-Then-Else

Do While

The ability to express a problem solution using only three basic patterns of control is called structured programming.



Simple Sequence Programs



Simple Sequence Control Structure

Represents the computer’s ability to execute instructions in step-by-step, sequential manner.It is the simplest and most frequently used of the three basic control structures.Previous Page Home Page Next Page End


FLOWCHARTS


Simple Sequence

An example of a simple sequence set of instructions not involving the use of a computer is the steps you might give a friend to get to a store. The steps must be followed in a sequential manner otherwise your friend may get lost and never find the store.

1. Proceed down Orange Street for two miles.

2. Turn right on Duke Street.3. Proceed on Duke Street.4. At fork, take Main Street to

the left.5. Proceed two blocks.6. Store is on the left (77 Main

Street.



Flowchart

Start

Proceed down orange street for two miles

Turn right on duke street

At fork, take main street to the left

Proceed two blocks

Store is on the left (77 Main Street)

Stop

A program flowchart is a pictorial representation of an algorithm.



Simple Sequence

A simple wake up algorithm:

1. Get out of bed

2. Brush teeth

3. Eat breakfast

4. Take shower

5. Get dressed

Start

Brush teeth

Eat Breakfast

Take shower

Get dressed Stop

Program

Flowchart

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Flowchart Symbols

Start – Every algorithm must have one entry point (Start) and one exit point (stop).

These are indicated by the ellipsis symbols, called terminal interrupt symbols. Start

Stop



Flowchart Symbols

Input/output Symbol – Reading data from an input medium or writing data to an output medium.



Flowchart Symbols

Process symbol – Shows any processing steps. It represents an operation or group of operations causing change in value, form or location of data.



Flowchart Symbols

Flow Line - shows sequence of operations arrowheads are required if linkage is not top-to-bottom or left-to-right.



Flowchart Symbols

Decision Symbol – shows decision-making operation, usually based on a comparison, that determines which of two or more alternative paths should be followed.



Flowchart Symbols

Connector - Shows exit to, or entry from, another part of the flowchart; if the to or from step is another page, a page reference should be stated.

B3 c2

FROM PAGE 3



Flowchart Symbols

Annotation symbol – Gives additional explanation; comments.

-------



Flowchart Symbols

Preparation symbol – An operation performed on the program itself for control, initialization, overhead, or cleanup. E.g. to set a switch, to place a limit value in the loop control variable and to initialize an accumulator.



Flowchart Symbols

Predefined Process – Used to identify a series of steps shown another flowchart.



Variables

Variables are data items whose values may change, or vary, during processing.

Variable names are created to represent, or refer to, these data items. They are used to give names to lactations where data should be stored.

Click for Hint



Variable Names

Choose variable names that are appropriate and gives an indication of what will be stored. Shorten names where possible.

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Simple Sequence Structure

The Simple Sequence Structure represents the computer’s ability to execute instructions in a step-by-step, sequential manner.

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Solution – Example 1

Pseudocode

Start

Print “Enter FARENHEIT value”

Read farenht

celsius = (fareneht – 32) * 5/9

Print farenht, celsius

stop

Start


Program Flowchart

Read farenht

Print farenht, celsius

Stop

celsius = fareneht – 32) * 5/9


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Example 1 – In Basic Language


input farenht

celsius = (fareneht – 32) * 5/9

Print “The farenheit temperature is: “; farenht

Print “The celsius temperature is: “; celsius

End

Click to

Run Program


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Problem- Using Simple Sequence

Example 2

A store needs a computer program to prepare a monthly bill for each customer. For simplicity, assume that each customer purchases (at most) one type of item each month. For each purchase, there will be four inputs: customer name, item, quantity purchased, and price. The output will be the customer’s monthly bill after a 10 per cent discount is taken before taxes and a 5 % sales tax is added.


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Pseudocode

Start

Print “Enter name, item, quantity, and price”

Read name, item, qty, price

amtod = qty * price

discount = amtod * 0.10

subbill = amtod – discount

taxes = subbill * 0.05

bill = subbill * taxes

Print name, item, bill

stop


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Start

Print “Enter name item, quantity and price”

Read name item, qty, price


amtod = qty * price

Program Flowchart

subbill = amtod - discount


bill =subbill + taxes


Stop


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Program in Basic

Print “Enter name, item, quantity, and price”

Input name, item, qty, price

amtod = qty * price


subbill = amtod – discount


bill = subbill * taxes


endClick to

Run Program


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Selection Control Structure

If-Then- Else



The IF-THEN- ELSE control structure indicates that at a particular time in processing, a choice between alternative paths, or sequence of instructions is to be made.

It is a conditional statement that causes execution of some statement depending on the truth value of a certain condition. If the condition is true, then the statement (s) after “then” are executed. If the statement is false then the statement (s) after “else” are executed provided that the else clause is present.

IF-THEN-ELSE CONTROL STRUCTURE



Example 1 - PseudocodeIf rain is falling then take umbrellaEndif


Rain is falling?

Take Umbrella

Start

Stop

Example 1 - Flowchart

Yes

No



Example 2 - Pseudocode

If rain is falling then take umbrellaElse don’t take umbrellaEndif


Rain is falling?

Take Umbrella

Start

Yes

No

Don’t take Umbrella

Stop

Example 2 - Flowchart


Selection Control Structure

Do while Control Structure Else



Do While Control Structure

The “Do While” structure is a repetition statement that allows you to specify that an action is to be repeated while some condition remains true.

For example:

while there are more items on my shopping list

Purchase next item and cross it off my list.




StartPrint “Enter two

numbers, (Enter 999 to end program):

Read xRead y

X = 999 ? Yes

No

X > y ?

Print “The first number

is greater”

Yes NoPrint “The

second number is greater”

Print x, y

StopDo While

Control Structure

Print “Enter next two numbers, (Enter 999 to

end program):

Read xRead y


Do While Control StructureStart

Print “Enter two numbers, (Enter 999 to end program):”

Read x

Read y

do while x not equal to 999

if x > y then

print “The first number is greater”

else

print “The second number is greater”

endif

Print x, y

Print “Enter next two numbers, (Enter 999 to end program):”

Read x

Read y

Enddo

Stop


Click toRun Program

in Basic


Introduction to Programming Enter Created by N. Nembhard.

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