1.1.1 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),

 

- Main functions

• Load and Store programs and data,

- optical and magnetic disk drives

- magnetic tapes

- etc.

 

• Communicate with users

- CRT driver

- keyboard

- mouse

- printer

 

• Communicate with process

- RS-232 data lines

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1.1.2 Some I/O Devices

 

• Teleprinters or Teletypes

- this technology is becoming obsolete very fast, but may be useful when permanent records of sessions

- inexpensive but slow

- 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

- Inexpensive and fast

- 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- outdated technology which allowed permanent recording of user entry on punched cards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

- Inexpensive and fast

- 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

- very inexpensive

- 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.