CS2301:Computer Programming 2

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Introduction to Computers

Programming Languages and

Algorithms

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In this Chapter we will learn:

1.1 Introduction

1.2 Computers: What is a Computer?

1.3 Computers: Hardware and Software?

1.4 Computer Organization

1.5 Classification of programming languages

1.6 Machine Languages, Assembly Languages and High-Level Languages

1.7 Programming Language, computer program and Computer

Programmer

1.8 Program developing life cycle?

1.9 What do we mean by algorithm?

1.10 Examples of algorithms

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OBJECTIVES

Computer

Is a device capable of performing computations and

making logical decisions.

Another definition:

(often referred to as hardware) are controlled by

software (i.e., the instructions you write to command

the computer to perform actions and make decisions).

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1.2 Computers: What is a Computer?

Software

◦ Set of instructions that tells the computer to perform specific tasks.

◦ Computers process data under the control of sets of instructions called

computer programs.

◦ These programs guide the computer through orderly sets of actions specified

by people called computer programmers.

◦ Software may be divided into:

◦ Operating systems e.g. (Windows 7)

◦ Application programs e.g. (Microsoft word)

1.3 Computers: Hardware and Software (cont.)

Hardware

◦ Computer hardware is the collection of physical elements

that constitutes a computer system and assist to the

input, process, storage, output ….

◦ Various devices comprising computer

Keyboard, screen, mouse, disks, memory, CD-ROM,

processing units, etc.

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1.3 Computers: Hardware and Software?

Five logical units of computer system

◦ Input unit (Mouse, keyboard)

◦ Output unit (Printer, monitor, audio speakers)

◦ Memory unit (Retains input and processed information)

◦ Central processing unit (CPU) which consists of:

Control unit (Supervises operation of other devices)

Arithmetic and logic unit (ALU):Performs arithmetic calculations and

logic decisions.

◦ Secondary storage unit (Hard drives, floppy drives)

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1.4 Computer Organization

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1.4 Computer Organization (Cont.)Hardware Components

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1.4 Computer Organization (Cont.)Hardware Components

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1.4 Computer Organization (Cont.)Hardware Components in Actions

Execution of an Instruction

Internet

◦ A collection of interconnected networks, all freely

exchanging information. Or Global network of computers.

◦ Internet has become one of the world’s premier

communication mechanisms.

World Wide Web

◦ Also called the Web, WWW, or W3

◦ Organizes Internet resources throughout the world into a

series of menu pages, or screens, that appear on your

computer.

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1.5 The Internet and the World Wide Web

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1.6 Classification of programming languages

Three types of computer languages1- Machine language

Language of Computer. Only language computer directly understands

“Natural language” of computer Defined by hardware designBinary digit (bit): The digit 0 or 1 Binary code: A sequence of 0s and 1sByte: A sequence of eight bits.

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1.7 Programming Languages

Early computers were programmed in machine

language.

To calculate wages= rates * hours in machine

language

100100 010001 //load

100110 010010 // multiply

100010 010011 // store

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1.7 Programming Languages(cont)

2- Assembly language

◦ English-like abbreviations representing elementary computer

operations.

Clearer to humans

Incomprehensible to computers

Example

load basepay

add overpay

store grosspay

Assembler: Translates a program written in assembly

language in to machine language.

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1.7 Programming Languages(cont)

Machine language Assembly Language

100100 LOAD

100010 STOR

100110 MULT

100101 ADD

100011 SUB

Example of instructions in Assembly Language and Machine Language

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1.7 Programming Languages(cont)

3- High-level languages

Include Basic, FORTRAN, COBOL, Pascal, C, C++, C# and Java

– Similar to everyday English

– Uses common mathematical notations

The equation: wages = rate* hours can be written in java as:

Wages = rate * hours;

Another Example:

grossPay = basePay + overTimePay

Compiler: translates a program written in a high-level language

in to machine language.

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1.7 Programming Languages(cont)

Programming:

Is a process of problem solving by using a programming language.

Programming Language:

A set of rules, symbols and special words used to write computer

program.

Computer program:

 is a list of instructions, written to perform a specified task on

a computer

Syntax:

Rules that specify which statements (instructions) are legal.

Algorithm

- Step–by–step problem solving processes using informal language.

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1.8 Programming Language, Computer Program, and Computer Programmer

Examples of Programming Languages: Fortran COBOL Pascal Ada Basic C C++ Objective-C Visual Basic Visual C# PHP Python JavaScript Java

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1.8 Programming Language, Computer Program, and Computer Programmer

A programmer, computer programmer, developer, coder, or software engineer: is a person who design, writes and maintains computer software.

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Computer Programmer

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1.9 What is program developing life cycle?

step1: Analyze the problem.

- Outline the problem and its requirements.

- Design steps (algorithm) to solve the problem.

Step 2: Implement the algorithm(coding).

- Implement the algorithm code.

- Verify that the algorithm works.

Step 3: Maintenance (when errors occurs)

- Use and Modify the program if the problem domain changes.

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1.9 What is program developing life cycle?

Understand the overall problem.

Understand problem requirements.

- Does program require user interaction?

Example: When you calculate the area of a rectangle What do we require

from the user?

Enter the length of the rectangle, width of the rectangle

- Does program manipulate data?

Example: Equation calculating the area of a rectangle

Area= length * Width

- What is output?

Note

If the problem is complex, divide into sub problems.

Analyze each sub problem as above.

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How Problem Analysis could be done

1.9.1 Defining the Problem The problem must be defined in terms of:

◦ Input: raw data to be processed.

◦ Output: production of useful information.

◦ processing: converting or transforming data into useful

outputs.

Keyboard ScreenProcessing

input data output data

1.9.2 Input and Output

Inputs

◦ Can come from many sources, such as users, files, and

other programs

◦ Can take on many forms, such as text, numbers,

graphics, and sound

Outputs

◦ Can also take on many forms, such as numbers, text,

graphics, sounds, or commands to other programs

1.9.3 The Problem Analysis-Coding-Execution Cycle

Stages of programming

1.9.3 The Problem Analysis-Coding-Execution Cycle

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Typical Java development environment.

1.10.1 The Algorithm

Methods for representing algorithms

Pseudo code Flow Chart

Note:Before use any two methods, you must specify the input,

processing, and output

Pseudo Code◦ An informal language similar to English

Is not considered programming language.

Helps programmers develop algorithms

Does not run on computers

Should contain input, output and calculation actions

Can be easily converted for different programming languages

such as Pascal, Java, C++.

1.10.2 The Algorithm- Pseudo Code

Example 1: Using pseudo code ,write suitable algorithm that

calculate the area and perimeter of rectangle and print

them.

Area=length * width

Perimeter=2(length * width)

◦ Prompt the user

◦ Input Length and width

◦ Calculate Area = length*width

◦ Calculate Perimeter = 2*( length + width)

◦ Output Area

◦ Output Perimeter

◦ End

Example 2: Using pseudo code write suitable algorithm that calculate and output Sum and Average of 5 numbers

Input five number x1, x2, x3, x4, x5

Calculate Sum = x1+x2+x3+x4+x5

Calculate Average = Sum/5

Output Sum

Output Average

end

Input grade Check if (grade > 60) then Print "passed" Else Print "failed“ End

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Example 3: Using pseudo code ,write suitable algorithm: If the student's degree is greater than or equal 60, print “pass” else print “fail”.

Example4: - Using Pseudo code, Write suitable algorithm: Calculate and print the average of temperature

degrees for the following readings T1, T2, T3.

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Answer:• Input T1, T2, T3• Calculate avg= (T1 + T2 + T3)/3• Output avg • End

Flow chart

Is a graphical way that explain the steps to solve

problem and how they relate to each other

(it is a symbolic representation of the algorithm).

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1.10.3 The Algorithm-Flow chart

Flow chartStart or Stop Program

Input or Output

Process, Calculate, Storage

Arrows determine the direction of the program's progress

Used to express logical operations or operations report(Condition)

Connection

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Condition Branching

Yes NoCompare

yesNo

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Condition Rotation

No

Yes

)1(

No

Yes

)2(

Sum = T1+T2+T3

- Example 5: - Using flow chart, Write suitable algorithm: - Calculate and print the average of temperature degrees for the following readings

T1, T2, T3.

start

Input T1, T2, T3

Avg = sum/3

Print avg

stop

Input : T1, T2, T3

claculation: Sum = T1+T2+T3Avg = sum/3

Output:Print Avg

Sum= T1+T2+T3

Example 6: - Using pseudo code and flow chart to

write suitable algorithm: - Calculate the average for temperature

for the following readings T1, T2, T3. - IF the average is greater than 15 print

the average, else print the weather is cold.

start

inputT1, T2, T3

Avg = sum/3

Print avg

avg > 15

Print “cold”

Stop

StartInput : T1,T2,T3Process and outputSum = T1+T2+T3

Avg = sum/3

If avg > 15 then

Print avg

Else

Print “cold” End if end

YesNo

Example7: Using flow chart to write an

algorithm. Enter number (X) and find the value (F), as shown in the following equations:

F= { x + 1 x >=0 x-1 x< 0

Flow chart start

Input x

Print F , x

X <= 0

End

YesNo

F= x+1 F = x-1

Example 8:Using pseudo code and flow chart to

write an algorithm. Enter number (X) and then find and print the value (Y), as shown in the following equation:

Y=(X-2)/X Note: (if X=0 enter value of X again)

Pseudo code input: X process: if x=0 Re-enter the new value of x because you can not divide by 0 Y=(X-2)/X output: Y

start

stop

Input X

Y=(X-2)/X

Print Y

If X=0 yes

No

Flow Chart

Discuss Using pseudo code and flow chart to write an algorithm that :

Accept 3 readings of temperature degrees and find the average then

check the average

if avg less than 15 : print the “cool air”

if avg between 15 and 25: Print “moderate air”

And if the avg is not verify the previous conditions: print “hot air”

Home Work (1)1. Using pseudo code and flow chart to write an algorithm that

calculate the area of a rectangle print it.Note: area of the rectangle = length × width.

2. Using pseudo code and flow chart to write an algorithm that find the area of a circle which its radius (R) and print it.Note: The area of a circle is equal to π * R2, where π is a constant value of approximately 3.14.

3. Using the methods (pseudo code and flow chart), we need to find and print the vicinity of the football stadium, and determine

4. whether if vicinity is greater than or equal to 600 m then print (international stadium) , and if vicinity is less than 600 then print (local stadium ),

Note: The perimeter of the rectangle is equal to (length + width)×2 .

End