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AN OVERVIEW OF
COMPUTERS &
PROGRAMMING
LANGUAGES
GOALS
 To understand the activity of programming
 To learn about the components of computers
 To learn about level of p...
What is Programming?
 Computer programming
 the art and science of designing and writing
computer programs.
 Computer p...
What is a computer?
 Hardware
 the physical, tangible parts of a computer
 keyboard, monitor, disks, wires, chips, etc....
Computer System Organization
Hardware
•CPU
•Main Memory (RAM)
•Secondary Storage
•I/O Device
Software
•System Programs
•Ap...
Hardware Components
of a Computer
Hardware Components
of a Computer – motherboard
processor chip
adapter cards
memory chips
memory slots
motherboard
Expansi...
Hardware Components of a Computer
CPU
Brain of the
computer, most
expensive, the
faster computer.
CPU components–
control ...
SECONDARY STORAGE
•Provides permanent storage for
information.
•Examples of secondary storage:
•Hard disks
•Floppy disks
•...
RAM vs Secondary Storage
 Primary memory
 volatile
 Fast
 Expensive
 Low capacity
 Works directly with the processor...
INPUT DEVICES
Sheet-fed
Hardware Components of a Computer
OUTPUT DEVICES
Hardware Components of a Computer
CPU and Main Memory
Central
Processing
Unit
Main
Memory
Chip that executes
program commands
Eg.
Intel Pentium 4
Sun ultraS...
Secondary Memory Devices
Central
Processing
Unit
Main
Memory
Floppy Disk
Hard Disk
Secondary memory
devices provide
long-t...
Input / Output Devices
Central
Processing
Unit
Main
Memory
Floppy Disk
Hard Disk
Monitor
Keyboard
I/O devices facilitate
u...
Software
 In contrast to hardware, software is an abstract, intangible
entity.
 Software can be categorized as system or...
Software Categories
 System Software
 Systems programs keep all the hardware and software running
together smoothly
 Th...
Algorithm
Algorithm refers to the strategy to solve a problem
It is a clear step by step sequence of instructions that
des...
Coding
Algorithm need to be translated into computer
language so that it can be executed
Coding refers to the process of e...
Digital Information
 Computers store all information digitally:
 numbers
 text
 graphics and images
 video
 audio
 ...
Representing Text Digitally
 For example, every character is stored as a
number, including spaces, digits, and punctuatio...
p. 4.15 Fig. 4-16 Next
The ASCII data set  128 characters (0 until 127)
Character A in ASCII  01000001
American Standard...
Binary Numbers
 Once information is digitized, it is represented
and stored in memory using the binary number
system
 A ...
Memory
24
Main memory is divided
into many memory
locations (or cells)
9278
9279
9280
9281
9282
9283
9284
9285
9286
Each m...
Storing Information
25
9278
9279
9280
9281
9282
9283
9284
9285
9286
Large values are
stored in consecutive
memory location...
Main Memory
Storage Capacity
 Every memory device has a storage capacity,
indicating the number of bytes it can hold
 Capacities are...
Language Levels
 Levels of programming language levels:
 machine language
 assembly language
 high-level language
 Ea...
Programming Languages
Machine language
101101100110 011011010
Assembly language
iload intRate
bipush 100
if_icmpgt intErro...
Programming Languages
 Each type of CPU executes instructions only in a
particular machine language
 A program must be t...
Language Description Examples Translator
Machine Instruction in 0
and 1 bits
0111000011000
001
None
Assembly Instruction i...
The Java Programming Language
 Created by Sun Microsystems, Inc.
introduced in 1995 and it's popularity has
grown quickly...
Java Translation
 The Java compiler translates Java source code
into a special representation called bytecode
 Java byte...
Java Translation
34
Java source
code (program)
Machine
code
Java
bytecode
Bytecode
interpreter
Java
compiler
Portability
 After compiling a Java program into byte-code, that
byte-code can be used on any computer with a byte-
code ...
Becoming Familiar with your
Computer to use Java
 Understand files and folders/directories
 Locate the Java compiler/ In...
A DOS Command Window
An Integrated Development
Environment
File Hello.java
1 public class Hello
2 {
3 public static void main(String[] args)
4 {
5 // display a greeting in the conso...
Java Program Elements
 A Java program is made up of class definitions.
 A class definition must contains a header and a
...
Java Program Structure
41
public class Hello
{
}
// comments about the class
class header
class body
//Comments can be pla...
Java Program Structure
42
public class MyProgram
{
}
// comments about the class
public static void main (String[] args)
{...
Compiling and Running
Type program into text editor
Save (file name must be similar to class name)
Open Dos Window
Change ...
Hello.java
javac
Hello.class
java
Class Loader
Processing a Java Program
Class Loader
 A Java program typically consists of several pieces
called classes.
 Each class may have a separate author...
JVM
Create/modify source code
Source code
Compile source code
Byte code
Run byte code
Output
Syntax errors
Runtime errors ...
Errors
 It is common for programmer to make mistake
in a program.
 Three kinds of errors
 Syntax errors
 Runtime error...
Syntax Errors
 Grammatical mistakes in a program
 The grammatical rules for writing a program are very
strict
 The comp...
Runtime Errors
 Errors that are detected when your program is
running, but not during compilation
 When the computer det...
Logic Errors
 Errors that are not detected during compilation or
while running, but which cause the program to
produce in...
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Introduction To Computer and Java

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Transcript of "Introduction To Computer and Java"

  1. 1. AN OVERVIEW OF COMPUTERS & PROGRAMMING LANGUAGES
  2. 2. GOALS  To understand the activity of programming  To learn about the components of computers  To learn about level of programming languages  To become familiar with your computing environment and your compiler  To compile and run your first Java program  To recognize 3 types of errors
  3. 3. What is Programming?  Computer programming  the art and science of designing and writing computer programs.  Computer program  a sequences of instructions written in a programming language to achieve a task/to solve a problem.
  4. 4. What is a computer?  Hardware  the physical, tangible parts of a computer  keyboard, monitor, disks, wires, chips, etc.  Software  programs and data  a program is a series of instructions  A computer requires both hardware and software  Each is essentially useless without the other
  5. 5. Computer System Organization Hardware •CPU •Main Memory (RAM) •Secondary Storage •I/O Device Software •System Programs •Application Programs Computer Organization
  6. 6. Hardware Components of a Computer
  7. 7. Hardware Components of a Computer – motherboard processor chip adapter cards memory chips memory slots motherboard Expansion slots for adapter cards
  8. 8. Hardware Components of a Computer CPU Brain of the computer, most expensive, the faster computer. CPU components– control unit, program counter, register instruction, arithmetic logic unit, accumulator. RAM Temporary memory, volatile, directly connected to the CPU, using memory cells unit.
  9. 9. SECONDARY STORAGE •Provides permanent storage for information. •Examples of secondary storage: •Hard disks •Floppy disks •Zip disks •CD-ROMs •Tapes. Hardware Components of a Computer
  10. 10. RAM vs Secondary Storage  Primary memory  volatile  Fast  Expensive  Low capacity  Works directly with the processor  Secondary Storage  Nonvolatile  Slow  Cheap  Large capacity  Not connected directly to the processor
  11. 11. INPUT DEVICES Sheet-fed Hardware Components of a Computer
  12. 12. OUTPUT DEVICES Hardware Components of a Computer
  13. 13. CPU and Main Memory Central Processing Unit Main Memory Chip that executes program commands Eg. Intel Pentium 4 Sun ultraSPARC III Primary storage area for programs and data that are in active use Synonymous with RAM
  14. 14. Secondary Memory Devices Central Processing Unit Main Memory Floppy Disk Hard Disk Secondary memory devices provide long-term storage Information is moved between main memory and secondary memory as needed Hard disks Floppy disks USB drives Writable CDs Writable DVDs Tapes
  15. 15. Input / Output Devices Central Processing Unit Main Memory Floppy Disk Hard Disk Monitor Keyboard I/O devices facilitate user interaction Monitor screen Keyboard Mouse Joystick Bar code scanner Touch screen
  16. 16. Software  In contrast to hardware, software is an abstract, intangible entity.  Software can be categorized as system or application software (refer next slide)  It consists of program and data to be used to perform certain tasks  A program is a sequence of simple steps and operations, stated in a precise language that the hardware can interpret  The process of programming involve algorithm design & coding.
  17. 17. Software Categories  System Software  Systems programs keep all the hardware and software running together smoothly  The most important system software is the operating system (OS)  controls all machine activities  provides the user interface to the computer  manages resources such as the CPU, memory & I/O  Windows XP, Unix, Linux, Mac OS  Application Software  generic term for any other kind of softwares  word processors, Spreadsheets, Web browsers, games
  18. 18. Algorithm Algorithm refers to the strategy to solve a problem It is a clear step by step sequence of instructions that describes how to accomplish a certain task. 2 ways can be used to represent algorithm: a) pseudocode - using english-like-phrases to describe the algorithm b) flowchart -using diagrams that employ the symbol to describe the algorithm.
  19. 19. Coding Algorithm need to be translated into computer language so that it can be executed Coding refers to the process of expressing algorithm in a programming language The product of coding is a program. The act of carrying out the instructions contained in a program is called program execution  A computer program is stored internally as a series of binary numbers known as the machine language of the computer
  20. 20. Digital Information  Computers store all information digitally:  numbers  text  graphics and images  video  audio  program instructions  In some way, all information is digitized - broken down into pieces and represented as numbers
  21. 21. Representing Text Digitally  For example, every character is stored as a number, including spaces, digits, and punctuation  Corresponding upper and lower case letters are separate characters H i , H e a t h e r . 72 105 44 32 72 101 97 116 104 101 114 46
  22. 22. p. 4.15 Fig. 4-16 Next The ASCII data set  128 characters (0 until 127) Character A in ASCII  01000001 American Standard Code for Computer InterChange (ASCII)
  23. 23. Binary Numbers  Once information is digitized, it is represented and stored in memory using the binary number system  A single binary digit (0 or 1) is called a bit  A byte consists of 8 bits.  Each byte in main memory resides at a numbered location called its address.
  24. 24. Memory 24 Main memory is divided into many memory locations (or cells) 9278 9279 9280 9281 9282 9283 9284 9285 9286 Each memory cell has a numeric address, which uniquely identifies it
  25. 25. Storing Information 25 9278 9279 9280 9281 9282 9283 9284 9285 9286 Large values are stored in consecutive memory locations 10011010 Each memory cell stores a set number of bits (usually 8 bits, or one byte)
  26. 26. Main Memory
  27. 27. Storage Capacity  Every memory device has a storage capacity, indicating the number of bytes it can hold  Capacities are expressed in various units: 27 KB 2 10 = 1024 MB 2 20 (over 1 million) GB 2 30 (over 1 billion) TB 2 40 (over 1 trillion) Unit Symbol Number of Bytes kilobyte megabyte gigabyte terabyte
  28. 28. Language Levels  Levels of programming language levels:  machine language  assembly language  high-level language  Each type of CPU has its own specific machine language  The other levels were created to make it easier for a human being to read and write programs 28
  29. 29. Programming Languages Machine language 101101100110 011011010 Assembly language iload intRate bipush 100 if_icmpgt intError High-level language if (intRate > 100) . . .
  30. 30. Programming Languages  Each type of CPU executes instructions only in a particular machine language  A program must be translated into machine language before it can be executed  A compiler is a software tool which translates from high level language into a specific machine language  An assembler translates from assembly language into a specific machine language 30
  31. 31. Language Description Examples Translator Machine Instruction in 0 and 1 bits 0111000011000 001 None Assembly Instruction in mnemonic code LOAD 3 STOR 4 ADD assembler High-level Similar to human language, FORTRAN, COBOL, Pascal, C, C++, Java… sum = 4 + 3; Compiler & interpreter Programming Languages
  32. 32. The Java Programming Language  Created by Sun Microsystems, Inc. introduced in 1995 and it's popularity has grown quickly since Rich library Platform-independent ("write once, run anywhere") or architecture-neutral
  33. 33. Java Translation  The Java compiler translates Java source code into a special representation called bytecode  Java bytecode is not the machine language for any traditional CPU  Another Java software tool, called an interpreter (or Java Virtual Machine (JVM)) , translates bytecode into machine language and executes it 33
  34. 34. Java Translation 34 Java source code (program) Machine code Java bytecode Bytecode interpreter Java compiler
  35. 35. Portability  After compiling a Java program into byte-code, that byte-code can be used on any computer with a byte- code interpreter and without a need to recompile.  Byte-code can be sent over the Internet and used anywhere in the world.  This makes Java suitable for Internet applications.
  36. 36. Becoming Familiar with your Computer to use Java  Understand files and folders/directories  Locate the Java compiler/ Install J2SE  Set path & Java class path  Write a simple program (later)  Save your work  Compile & run  Use Dos Command Prompt or IDE
  37. 37. A DOS Command Window
  38. 38. An Integrated Development Environment
  39. 39. File Hello.java 1 public class Hello 2 { 3 public static void main(String[] args) 4 { 5 // display a greeting in the console window 6 System.out.println("Hello, World!"); 7 } 8 }
  40. 40. Java Program Elements  A Java program is made up of class definitions.  A class definition must contains a header and a body.  A class contains zero or more methods  A method is a named section of code that also has a header & body  A method contains program statements  Single-line (starts with //) and multi-line (enclosed by /* and */) comments are used to document the code
  41. 41. Java Program Structure 41 public class Hello { } // comments about the class class header class body //Comments can be placed almost anywhere
  42. 42. Java Program Structure 42 public class MyProgram { } // comments about the class public static void main (String[] args) { } // comments about the method method header method body
  43. 43. Compiling and Running Type program into text editor Save (file name must be similar to class name) Open Dos Window Change directory to saved file directory Compile into byte codes javac Hello.java Execute byte codes java Hello
  44. 44. Hello.java javac Hello.class java Class Loader Processing a Java Program
  45. 45. Class Loader  A Java program typically consists of several pieces called classes.  Each class may have a separate author and each is compiled (translated into byte-code) separately.  A class loader (called a linker in other programming languages) automatically connects the classes together and loads the compiled code (bytecode) into main memory.
  46. 46. JVM Create/modify source code Source code Compile source code Byte code Run byte code Output Syntax errors Runtime errors or incorrect results Creating a Java Program…
  47. 47. Errors  It is common for programmer to make mistake in a program.  Three kinds of errors  Syntax errors  Runtime errors  Logic errors
  48. 48. Syntax Errors  Grammatical mistakes in a program  The grammatical rules for writing a program are very strict  The compiler catches syntax errors and prints an error message.  Example: using a period where a program expects a semicolon  System.out.print("..."),  System.out.print("Hello);
  49. 49. Runtime Errors  Errors that are detected when your program is running, but not during compilation  When the computer detects an error, it terminates the program and prints an error message.  Example: attempting to divide by 0
  50. 50. Logic Errors  Errors that are not detected during compilation or while running, but which cause the program to produce incorrect results  Example: an attempt to calculate a Fahrenheit temperature from a Celsius temperature by multiplying by 9/5 and adding 23 instead of 32  E.g  System.out.print("Hell");
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