ch01_overview computer science and engineering.pdf

CSE 115 Programming Language I ECE@NSU
Overview of Computers
and
Programming
Mirza Mohammad Lutfe Elahi

2
Outline
• Overview of Computers
– Hardware
– Software
• Computer Languages
• Software Development Method
• Pseudo Code and Flowcharts
• Professional Ethics

3
Computers
• Computers receive input, store, process, and output
information.
• Computer can deal with numbers, text, images,
graphics, and sound.
• Computers are worthless without programming.
• Programming Languages allow us to write programs
that tell the computer what to do and to provide a way
to communicate with computers.
• Programs are then converted to machine instructions
so the computer can understand it.

4
Hardware & Software
• Hardware is the equipment used to perform the
necessary computations.
– Central Processing Unit (CPU), memory, disk storage,
monitor, keyboard, mouse, printer, etc.
• Software consists of the programs that enable us to
solve problems with a computer by providing it with a
list of instructions to follow
– Windows OS, MS Word, Mozilla Firefox, etc.

5
Computer Hardware
• Main Memory
– RAM - Random Access Memory - Memory that can be read and written in any
order (as opposed to sequential access memory), volatile.
– ROM - Read Only Memory - Memory that cannot be written to, non-volatile.
• Secondary Memory: Magnetic hard disks, Flash (solid state)
disks, Optical disks (CDs and DVDs).
• Central Processing Unit (CPU): Executes all computer
operations and perform arithmetic and logical operations.
• Input/Output Devices: keyboard, mouse, scanner, monitor,
printer, and speakers.
• Computer Networks – Computers that are linked together can
communicate with each other.

6
Components of a Computer

7
Memory
• Memory: a large collection of memory cells
• Each Memory Cell has an address and a value
• Bit: Binary digit = Either 0 or 1
• Byte: Made up of 8 bits
• Memory Address: position of a memory cell
• Memory Content: Value stored in memory
– Every memory cell has content, whether we know it or not
• Memory capacity
– Kilobyte (KB) = 210 = 1024 Bytes; Megabyte (MB) = 220 Bytes > 106 Bytes
– Gigabyte (GB) = 230 > 109 Bytes; Terabyte (TB) = 240 Bytes > 1012 Bytes
65
One bit
Byte = 8 bits
.
.
. Byte at
address 16
value = 65
.
.
.
0
1
2
3
16
17
18
Memory
Addresses

8
Computer Software
• Operating System - controls the interaction between
machine and user. Examples: Windows, Linux, etc.
– Communicates with computer user.
– Collects input and Displays output.
– Manages memory and processor time.
– Manages Storage Disk.
• Application Software - developed to assist a computer
user in accomplishing specific tasks. Example: MS
Word, Google Chrome, etc.

9
Computer languages
• High-level Language: Combines algebraic expressions and
high-level commands
– High Level : Very far away from the actual machine language
– Examples: Fortran, C, Prolog, C#, Perl, and Java.
• Machine Language: A collection of machine instructions
– Not standardized. There is a different machine language for every
processor family.
• Assembly Language: uses symbols (called mnemonics) that
correspond to machine language instructions.
– Low level: Very close to the actual machine language.

10
Compiler
• Compilation is the process of translating the source code (high-
level) into executable code (machine level).
• Source file: contains the original program code
– A Compiler turns the Source File into an Object File
• Object file: contains machine language instructions
– A Linker turns the Object File into an Executable
• Integrated Development Environment (IDE): a program that
combines simple text editor with a compiler, linker, loader, and
debugger tool
– Examples: Code::Blocks, Eclipse, Visual Studio, etc.

11
Editing, Translating, Linking, and
Running High-Level Language Programs

12
Flow of Information During Program
Execution

13
Software Development Method
1. Specify problem requirements
2. Analyze the problem
3. Design the algorithm to solve the problem
4. Implement the algorithm
5. Test and verify the completed program
6. Maintain and update the program

14
Steps Defined
1. Problem: statement that specifies the problem that should be
solved on the computer.
2. Analysis: Understanding the problem and identifying the
inputs, outputs, and required computation.
3. Design - Designing and developing the list of steps called
algorithm to solve the problem.
4. Implementation: writing the algorithm as a program using a
given programming language.
5. Testing - Testing requires checking and verifying that the
program actually works as desired.
6. Maintenance - Maintaining involves finding previously
undetected errors and keep it up-to-date.

15
Converting Miles to Kilometers
1. Problem: Your boss wants you to convert a list of miles to
kilometers. Since you like programming, you decide to write
a program to do the job.
2. Analysis
• We need to receive miles as input
• We need to output kilometers
• We know 1 mile = 1.609 kilometers
3. Design
1. Get distance in miles
2. Convert to kilometers
3. Display kilometers

16
Implementation in C Language
/*
* Converts distance in miles to kilometers.
*/
#include <stdio.h> // printf, scanf definitions
#define KMS_PER_MILE 1.609 // conversion constant
int main(void) {
float miles, // input – distance in miles
kms; // output – distance in kilometers
/* Get the distance in miles */
printf("Enter the distance in miles> ");
scanf("%f", &miles);
/* Convert the distance to kilometers */
kms = KMS_PER_MILE * miles;
/* Display the distance in kilometers */
printf("That equals %f kilometers.n", kms);
return 0;
}
Sample Run:
Enter the distance in miles> 10.0
That equals 16.090000 kilometers

17
Converting Miles to Kilometers
5. Test: We need to test the previous program to make sure it
works. To test we run our program and enter different values
and make sure the output is correct.
6. Maintenance: Next time, your boss wants to add a new feature,
so he wants you to add support for converting different units.

18
Pseudo Code and Flowchart
• Algorithm - A list of steps for solving a problem.
• Pseudo code - A combination of English phrases and
language constructs to describe the algorithm steps.
• Flowchart - A diagram that shows the step-by-step
execution of a program

19
Why Use Pseudo Code?
• The benefit of pseudo code is that it enables the programmer to
concentrate on the algorithm without worrying about all the
syntactic details of a particular programming language.
• In fact, you can write pseudo code without even knowing what
programming language you will use for the final
implementation.
• Pseudo code cannot be compiled or executed, and does not
follow syntax rules. It is simply an important step in producing
the final code.
• Example:
Input Miles
Kilometers = Miles * 1.609
Output Kilometers

20
Another Example of Pseudo Code?
• Problem: Calculate your final grade for CSE 115
• Specify the problem: Get different grades and then compute
the final grade.
• Analyze the problem: We need to input grades for quizzes,
assignments, exams, class performance and the percentage
each part counts for. Then we need to output the final grade.
• Design
1. Get the grades: exams, quizzes, assignments, and labs.
2. Grade = 0.2 * Quizzes + 0.1 * Assignments + 0.25 * Midterm Exam +
0.4 * Final Exam + 0.05 * Class Performance
3. Output the Grade
• Implement and Test: Learn how to program in C, Write the
program, then input some test values, calculate and check the
final grade.

21
Flowchart
Process Start or Terminal
Decision Document
Display Manual Input

22
Example of Flowchart
Start
Get Grades and
percentages
Calculate
Final grade
Display
Grade
End

23
Professional Ethics
• Privacy and Misuse of Data
– computer theft (computer fraud) - Illegally obtaining
money by falsifying information in a computer database
• Computer Hacking
– Virus - Code attached to another program that spreads
through a computer’s disk memory, disrupting the computer
or erasing information
– Worm - A virus that can disrupt a network by replicating
itself on other network computers

24
Professional Ethics
• Plagiarism and Software Piracy
– Software piracy – Violating copyright agreements by
illegally copying software for use in another computer
• Misuse of a Computer Resource

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