Introduction Lecture

Hardware vs Software

Hardware = physical components, electronics, peripherals

Computer Components (Hardware)

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

Main types:

System Software / Operating System

Hierarchical File structure

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

Dialog Boxes


Software Compatibility

Many companies make the same kinds of applications:

Incompatibility exists between:

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


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):
some comparisons:
ASCII code translates characters on keyboard into a number between 0 and 255, stored as a byte
example: 01000001 = 65 = A

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