Introduction to Computers and
Programming
CS0007: Introduction to Computer Programming
Programming – Why?
 Computers are used for many different purposes in many
different situations.
 But, how can they be so versatile?
 Answer: They can be programmed
 The ability for a computer to be programmed allows it to do
whatever their programs tell them what to do.
 A program is a set of instructions that tell a computer what
to do.
 A computer cannot do anything unless it has a program to
tell it what to do.
 In this class, we will focus on writing these programs.
Programming – What?
 Programs are used to operate the components of a computer,
solve problems or satisfy a want/need.
 How long will it take me to get home if I drive x miles per hour?
 I want to be able to tell my friends what I am doing right now.
 Computer Programming is both an Art and a Science
 Every aspect of a program must be carefully designed
 As an art, programming takes creativity and problem solving.
 There is often no one correct way to solve a problem.
 As a science, there are formal and proven methods to go about
creating a programming.
 In this course, you will learn both the art and science of
programming.
Hardware and Software
 Programs can also be called software.
 Software refers to the computer programs that a computer uses to
complete a task.
 Hardware refers to the physical components that a computer is
made of.
 A computer is not one device, but a system of devices working in
tandem.
 Each device plays a part.
 Major components:
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Central Processing Unit
Main Memory
Secondary Storage Devices
Input Devices
Output Devices
Central Processing Unit (CPU)
 The CPU is the heart and brain of the computer.
 The CPU continuously does the following things:
1.
2.
3.
Fetch an instruction
Follow the instruction
Produce some resulting data
 The CPU has two parts:
 Control Unit
 Coordinates the computer’s operations
 Determines where to get the next instruction
 Regulates the other major components of the computer
 Arithmetic and Logic Unit (ALU)
 Designed to perform mathematical operations
Main Memory
 Main memory holds information that the CPU needs to access quickly.
 Namely, the instructions to be executed.
 When a program is running, some or all of its instructions are in main
memory.
 Memory is divided into sections called bytes that hold equal amount of
data.
 Each section is made up of 8 bits.
 A Bit is the most basic unit of information a computer can hold. It is a
switch that is either on (1) or off (0)
 Each byte is assigned and can be accessed by its address.
 A Memory Address is a unique identifying number associated with a byte in
memory.
 Main memory typically is volatile.
 Volatile Memory – is memory that when it loses power, the contents are
erased.
Secondary Storage
 Secondary Storage is memory that can hold data for a long period of time.
 Programs are usually stored in secondary storage and loaded into main memory
as needed.
 This forms a hierarchy typically called the memory hierarchy.
 Common forms of secondary storage:
 Hard Drive
 Disk Drive
 Solid State Drive
 Removable Storage
 Floppy Disk
 CD-ROM
 USB Drives
 Other files can be stored in secondary storage:
 Documents
 Pictures
 Whatever else you save on your computer
Input Devices
 Input is any data the computer collects from the outside
world.
 An Input Device is anything that collects data and sends it to
the computer.
 Common Input Devices:
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Keyboard
Mouse
Scanner
Digital Camera
Disk Drive
USB Drive
Output Devices
 Output is any data the computer sends to the outside world.
 An Output Device formats data and presents it to the outside
world.
 Common Output Devices:
 Monitor
 Printer
 Disk Drive
 USB Drive
Software
 Software refers to the programs that run on a computer.
 Two main categories (for this class):
 Operating System (OS)
 A set of programs that manages a computer’s hardware devices and
controls their processes.
 Most modern operating systems are capable of running multiple
programs at once.
 UNIX, Linux, Mac OS X, and Windows are examples
 Application Software
 Programs that make the computer useful for the user
 Solve specific problems or supply a service
 Word processors, spreadsheets, databases, etc.
 This is what we will be developing in this class.
Program Development Cycle
 Many programmers follow a sequence of Steps to create their
programs.
1. Analyze – Define the Problem
Make sure that you understand what the program should do.
What should the user be able to enter? How? How does the
program come up with an answer? What does the program
output? How?
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User – a person who uses a computer program.
End User – the user that the program was made for.
Design – Plan a Solution for the Problem
2.
Develop a PRECISE sequence of steps to solve the problem
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An algorithm is a precise sequence of steps to solve a problem.
Develop an Algorithm
 Imagine you want a program that tells a user how many
stamps they need in order to mail a certain number of pages.
 You need one stamp for every 5 pages
 6 pages = 2 stamps
 12 pages = 3 stamps
…
 Write an algorithm (the steps needed) to solve this problem
Program Development Cycle – Design
(Continued)
 Typically a program follows three general steps
Input
2. Processing (Formulas)
3. Output
1.
Develop an Algorithm, 2nd Attempt
 OK, with this knowledge, try writing the algorithm again
Program Development Cycle – Design
(Continued)
 Are those three steps enough?
 What about if the user enters “Banana” instead of a number of sheets?
 The program does not know how to find the number of stamps required to mail
“Banana” number of sheets
 In order for the program to run without crashing, our algorithm must make
sure that the user inputs some valid data.
 There are two main ways of doing this:
1.
Prevention – Making sure that the user is not physically able to enter in invalid data.
2.
Validation – Allowing the user to enter invalid data, but checking it to make sure it is
valid before processing.
So, there are really 4 general steps most programs follow:
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Input
1.
1.
2.
2.
3.
Read Input
Validate Input
Process
Output
Develop an Algorithm, 3rd Attempt
 OK, now with THAT information, try developing the
algorithm
 One good algorithm developed could look like this:
1.
2.
3.
4.
5.
Request the number of sheets of paper from the user; call it
Sheets (Input/Read)
Make sure Sheets is a positive whole number
(Input/Validation)
Divide Sheets by 5 (Processing)
Round the result from step 3 up to the highest whole
number; call it Stamps (Processing)
Reply with the number Stamps (Output)
Programming Tools
 Flowcharts – A chart that consists of symbols connected by
arrows. Within each symbol is a phrase presenting the
activity at that step. The shape of the symbol indicates the
type of operation that is to occur.
 Hierarchy Charts – A chart that shows the overall program
structure. These charts describe what each part, or module,
does and how they are related. These modules intentionally
omit details of how they work.
 Pseudocode – an abbreviated plain English version of actual
computer code. Kind of a mix between English and code.
THERE IS NO OFFICIAL SYNTAX TO PSEUDOCODE.
Flow Charts
 Flow Line - indicates the flow of logic
 Terminal – indicates the start or end of a task
 Input/Output – used for input or output operations. What is
to be input or output should be in the figure.
Flow Charts
 Processing - used to show a processing step. The
instructions are displayed in the figure.
 Decision – used to show when a decision needs to be made.
Lines for yes and no come out of it. The question is displayed
in the figure.
 Connector – Used to join flow lines.
Stamps Flowchart
Start
Read
Sheets
Display Error
Message
No
Is sheets a
positive
whole
number?
Yes
Set Stamps =
Sheets/5
Round Stamps to
nearest whole number
Display
Stamps
End
Hierarchy Chart
Postage Stamp
Program
Calculate
Stamps
Input
Read Sheets
Validate Sheets
Set Stamps =
Sheets/5
Round Stamps to the
next whole number
Display Stamps
Program Development Cycle
Write the Code – Implement a solution
3.
The instructions in a programming language collectively
called code.
Your code should be a translation of your algorithm
developed into the programming language.
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In this class we use Java, but there are many other programming
languages: C, C++, C#, Ruby, Python, Visual Basic, etc.
This is the major focus of this course, but note that you need
to be able to think algorithmically in order to do this.
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Meaning, you need to be able to logically solve the problem in order to
write a program for it.
Program Development Cycle
Testing and Debugging – Locate and remove any errors in the
program
4.
Testing is the process of finding errors in a program
Debugging is the process of removing errors in a program.
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An error in a program is called a bug.
We will talk more specifically about the kinds of errors that can occur in
a program once we start programming.
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Complete All Documentation – Organize the material that describes
the program.
5.
Documentation is any material whose purpose is to allow another person
or programmer to use or understand the program
Two kinds of documentation:

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1.
2.
External Documentation – Material outside of the code files that describe the
program.
Internal Documentation – Lines inside of a code file that do nothing except
describe details of the program. In Java, these are called comments.