Transcript Chapter 2 Lecture Notes - Austin Community College

Chapter 1 Lecture Notes
Bill Tucker
Austin Community College
COSC 1315
Copyright © 2002 W. A. Tucker
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Programming
• Programming is Problem Solving
• People use programs to “solve problems”
• Designing a program is like “solving a
problem”
• Make a program run properly is also
“solving a problem”
Copyright © 2002 W. A. Tucker
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My Favorite Phrase
• The computer made a mistake!
• Computers don’t make mistakes unless
they are BROKEN
• People make mistakes
• People write programs
• People write programs that make mistakes
Copyright © 2002 W. A. Tucker
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Computer Hardware
• The main parts of a computer are
– Memory
• Main memory
– RAM
– Volatile memory
• Secondary memory (secondary storage)
– Files
– Non-Volatile
– Input / Output
– Central Processing Unit
Copyright © 2002 W. A. Tucker
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Processing Data
• Processing of data occurs within the CPU
– Data must be moved from storage to the CPU for
processing to occur
– The CPU must be told where the data is located
– All data stored in main memory is referenced by a
memory address
– Example: A = B + 12
• Get the contents of memory location 00BE34 (B)
• Add 12 to the value
• Store the value into memory location 00BE38 (A)
Copyright © 2002 W. A. Tucker
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Computer Software
• Operating Systems manage and control
the resources of a computer
– EX: Windows 98, Windows 2000,
Windows XP, UNIX, Lynix, MAC/OS, etc
– Most operating systems provide a graphical
user interface (except UNIX and Lynix)
• Application Software
– Programs written to perform a specific task
– EX: Office 2000, Office XP, Quicken, etc.
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Computer Instructions
• Programmers must “tell the computer what
to do”
• The computer will do exactly what the
programmer tells the computer to do,
nothing more and nothing less.
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Computer Language
• Computers understand only the binary
number system (zeros and ones)
– All data stored in the computer is stored as a
series of zeros and ones
– All instructions telling the computer what to do
are stored as a series of zeros and ones
• People do not naturally think in terms of
zeros and ones (the binary number
system)
Copyright © 2002 W. A. Tucker
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Programming Languages
• Programming languages allow a programmer to
give the computer instructions in a manner that
the programmer can understand
• Assembly Language is a low level language,
where the programmer uses a mnemonic
(abbreviation) to communicate an instruction to
the computer
– EX: “A” or “add” for addition
• This mnemonic is translated into machine
language (binary) by a program called an
assembler
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More on Programming Languages
• Assembly language is a one for one mapping to the
machine language and has to be rewritten for each
machine (not all machine languages are the same)
• An Assembler translates assembler code into
machine language that a computer may execute
• High level languages were created to allow
programmers to write at a level where one
programming instruction is converted into several
machine language instructions and to avoid having
to constantly rewrite the program
• A compiler converts high level language into
machine language that a computer may execute
Copyright © 2002 W. A. Tucker
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Examples of Languages
• High Level Languages
– BASIC, C, COBOL, FORTRAN, PASCAL
• Object Enabled Languages
– C++
• Object Oriented Languages
– Java, C#
Copyright © 2002 W. A. Tucker
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Development Environment
• Developing a program in a high level
language requires certain tools
– Editor – type in a program and save as a file
(called the source program)
– Compiler – converts source program into
machine language (called the object program)
– Linker – Combines object program with other
programs (include files) to produce
executable code (called the load module)
– Loader – Loads executable code into memory
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Integrated Development
Environment (IDE)
Editor
Source
File
.cpp extension
Compiler
Object
File
Syntax
Errors
Linker
Linker
Errors
Object
File
Loader
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.exe extension
Loader
Errors
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Software Development Method
1) Specify the problem
2) Analyze the problem
3) Design the algorithm to solve the problem
- Desk Checking
4) Implement the Algorithm
- Coding
5) Test and verify the completed program
- Compiling and Executing
6) Maintain and update the program
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Structured Programming
• Dividing a larger problem into smaller parts
– AKA: tops-down design, stepwise refinement,
modular programming
– Identify what steps need to be done, usually VERBS
– (ie: calculate, process, get, display, etc)
• Each smaller part is then solved using one of
three types of programming structure
– Sequential structure
– Selection structure
– Repetition (looping) structure
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Procedural Solutions
• Using structured programming, most
problems can be solved using the
following general procedural steps
– Get the input
– Process the input
– Display (output) the results
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Object Oriented Programming
• Humans interact with objects every day
– Driving a car
– Purchasing groceries
• OOP involves defining the attributes (data)
and behaviors (operations) of objects
(usually NOUNS)
• Combining these attributes and behaviors
into a class is called encapsulation
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Advantages of Objects
• Once an object is designed, implemented
and tested everyone can use it
– Improves productivity
– Supports portability or reuse of code
– All of which reduce development time
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