Introduction Lecture

Hardware vs Software

Hardware = physical components, electronics, peripherals

Computer Components (Hardware)

• Central Processing Unit (CPU)
• Memory (RAM)/Storage Devices (Disks)
• Input Devices (Keyboard, Mouse)
• Output Devices (Monitor, Printer)

Software = programs and data used by computer and stored on disk

Main types:

• application: program designed to do a "real world" task (eg. word processor)
• data: output created or used by an application (eg. MS Word document)
• system software: used internally to keep computer running (eg. operating system)

System Software / Operating System

• Loaded on boot up
• Controls how user interacts with the computer
• Interprets commands between you and CPU
• Examples: System X (Mac), WindowsXP (PC)

Hierarchical File structure

• Important file/data storage concept on most computers.
• Use of folders (directories) within folders (directories) to create "tree structure"
• useful for disk organization - relating relevant topics/info
• Use of a path to uniquely determine the location of a file

Common Aspects of Programs: Consistency and Redundancy

Importance of consistency across interface

Example: cut and paste commands always under Edit menu

Many ways to do the same command (toolbar, menu, keyboard shortcut)

Example: MS Word - Save command

Pull Down menus

• all options are shown (Office 2000 has smart menus where some options can be hidden)
• Less to remember
• CONSISTENCY:
  • Learning 1 helps many
  • All apps take advantage of similar features
  • More you use, more familiar you get
• REDUNDANCY:
  • Easy to find commands used most often
  • Accommodates for different styles
  • If one doesn't work, try another

Dialog Boxes

• Small windows open as a response to command in program
• Display message to user (example: ERROR MESSAGE)
• Solicit a response from the user (Opening a file)

WYSIWYG

• "What You See Is What You Get"
• What's on the screen = what's printed on paper
• Important concept for most applications
• Almost necessary for good/efficient word processing

Software Compatibility

Many companies make the same kinds of applications:

• Word Processors
  • MS Word
  • Ami Pro
  • Word Perfect
  • Word Star
• Spreadsheets
  • Excel
  • Lotus

Incompatibility exists between:

• Different brands of the same application (MS Word vs. Wordperfect)
• Different versions of the same software (Word 2003 vs. Word 2000)
• Different types of applications (graphics program vs. spreadsheet)
• Different operating systems (Windows XP vs. UNIX vs. Macintosh)

How to transfer data from one to another

Two possibilities

1. All programs read & write each other's files
2. Universal format that all programs can read & write = ASCII

ASCII

• Code used to represent letters (upper and lower case), numbers 0-9, and punctuation marks (everything on the keyboard) for storing information
• Cannot store styles, bold, italics, fonts, sizes, graphics, layouts

Digital vs. Analog

Digital = 2 discrete states: on/off, 1/0

example: light switch

Analog = continuous change between min and max

example: dimmer switch

Bits vs. Bytes

Bit = smallest piece of storage info (one switch, either 0 or 1)

n bits = 2ⁿ values

Byte = 8 bits = 256 values

used to represent one character

units commonly used (approximations):

• Kilobyte = KB = 1000 bytes
• Megabyte = MB = 1 million bytes = 1000 KB
• Gigabyte = GB = 1 billion bytes = 1000 MB
• Terabyte = TB = 1 trillion bytes = 1000 GB

some comparisons:

• low density floppy disk: 800 KB
• high density floppy disk: 1.4 MB
• standard hard drive: 5-20 GB
• standard amt. of RAM in a home computer: 64-256 MB
• amt. of space taken up by a 20 page paper of ASCII text: ~30KB

ASCII code translates characters on keyboard into a number between 0 and 255, stored as a byte

example: 01000001 = 65 = A