3.1 BASIC COMPONENTS
A computer has the basic properties,
- Inputs and outputs data
3.1.1 The components of a computer are,
The Central Processing Unit (CPU),
- Control Unit - processes machine language instructions
- Arithmetic Logic Unit - performs mathematical operations faster by using specialized hardware
- Cache - most new computers incorporate a local block of memory which is faster than remote memory. A copy of remote memory is stored here so that the CPU may work faster
Memory,
- Random Access Memory (RAM) - memory used for temporary storage of programs and data while the computer is on.
- Read Only Memory (ROM) - permanent software and data is stored in ROM, so that the CPU may always access this. A common use for this is a `start-up' routine, which allows a computer to load the operating system off of a disk.
- ROM (traditional) - a chip which is made to store the program, this may not be changed.
- PROM - a chip which the program may be `burned' into once.
- EPROM - memory is `burned' in, but may be erased using ultraviolet light, and rewritten.
- EEPROM - similar to EPROM, but may be electrically erased.
Input/Output (I/O),
Load and Store programs and data,
- optical and magnetic disk drives
3.1.2 Some I/O Devices
Teleprinters or Teletypes
- this technology is becoming obsolete very fast, but may be useful when permanent records of sessions
- can be operated at a distance by telephone
- allows user input by keyboard, and output on printed paper
Cathode Ray Tube (CRT)
- the preferred display device
- very flexible and user friendly
- Available in color, and varying sizes
- used for graphical and text output
- can be used with features such as touch screen input for harsh factory floor environments
Card Readers and Card Punches
- outdated technology which allowed permanent recording of user entry on punched cards
Printers
- Very popular method of permanent output
- Can produce varying qualities of print
- color printers available
- letter size paper output most common
Magnetic and Optical Disks and Tapes
- Inexpensive methods for transferring and storing data and programs
- storage capacity ranges from Kilobytes to Gigabytes, and capacities are increasing quickly
- Some are read and write only
- costs are very low per Megabyte, and are still dropping
- Storage media is still somewhat fragile, and requires certain level of protection
- Older tapes and systems are oriented towards backup, but newer methods allow random access.
mouse/button boxes/dial boxes/tablets/etc
- Various input peripherals make input easier
- most allow continuous input more suited to user
- allows more complex programs for user interaction
- the mouse has become the most popular input device
- most of these devices are not suited for the factory floor
keyboard
- the time honored standard for input
- now very inexpensive, used by almost all computers
- can be used by all people, and is universally understood
Special Application Boards
- becoming very inexpensive, and common
- A/D and D/A boards allow interfacing to applications which are monitored and/or controlled by analog signals (these are very inexpensive). These are the main source of interface to Sensors
- Video processing - allows video camera inputs to be read into memory, and the still pictures may then be used for vision processing.
