Download Introduction to Computers and Programming in Java

CS140, TSU
Introduction to Computers and Java
by Li Ma
Overview of CS120
CS120 is an integrated introduction to problem solving using computers, which teaches students
how real-world problems can be solved using computer programming languages
Concepts and techniques covered in CS120:
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data representation and number systems
basic components of computer systems
problem solving strategies
introduction to algorithms and pseudo code
introduction to programming languages
introduction to operating systems
Introduction to Computers
Computer systems
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hardware components
o input devices, output devices, memory, CPU, ALU, secondary storage,
communication devices, …
software components
o system software: operating systems, utility programs
o application software
Data hierarchy
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Bits: the smallest data items
Characters: a character – 1 byte – 8 bits, American Standard Code for Information
Interchange (ASCII)
Fields: a group of characters or bytes that conveys meaning
Records: several related fields
Files: a group of related records
Computer Organization
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Input unit
Output unit
Memory unit
ALU
CPU
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CS140, TSU

Introduction to Computers and Java
by Li Ma
Secondary storage unit
Programming languages
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Machine languages: strings of bits, slow and tedious
Assembly languages: English-like abbreviations, need too many instructions
High-level languages
Object-Oriented Programming and Java
Object-oriented programs are often easy to understand, correct, and modify. Objects (class
objects) are essentially reusable software components in an object-oriented program
The key object-oriented programming concepts
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Method: house the program statements that actually perform the tasks, but hide them
from the users
Class: program unit that house the set of methods that perform the class’s tasks
Object: an instance of the class
Reuse: a class can have many objects
Method call: send messages to an object
Instance variables: hold attributes of the object
Encapsulation: classes wrap attributes and methods into objects (information hiding)
Inheritance: the new class absorbs the characteristics of an existing class, possibly
customizing them and adding unique characteristics of its own
Polymorphism: a variable can reference objects of different types, can use the correct
methods regarding to the type of the referenced object
Java is one of the object-oriented programming languages. A key goal of Java is to be able to
write programs that will run on a great variety of computer systems and computer-control
devices.
Java development environment:
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Java SE Development Kit (JDK) for Windows
Java compiler (javac) and Java interpreter (java) on Microsoft Command Prompt
JCreator LE
Five phases to create a Java program:
1. Edit: => source code (*.java), editor
2. Compile: => bytecode (*.class), compiler
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CS140, TSU
Introduction to Computers and Java
by Li Ma
3. Load: transfer the bytecodes to the primary memory, class loader
4. Verify: examine the bytecodes, bytecode verifier
5. Execute: run the bytecodes
The Programming Process
1. Clearly define what the program is to do
2. Visualize the program running on the computer
3. Use design tools such as hierarchy chart, flowcharts, or pseudocode to create a model of
the program
4. Check the model for logic errors
5. Type the code, save it, and compile it
6. Correct any errors found during compilation. Repeat steps 5 and 6 as many times as
necessary
7. Run the program with test data for input
8. Correct any errors found while running the program. Repeat steps 5 through 8 as many
time as necessary
9. Validate the results of the program (output)
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