LESSON 2: INTRODUCTION TO COMPUTING (2)
ARE COMPUTERS ?(2)
RANDOM ACCESS MEMORY (RAM)
Think of a computer as a human brain. Your brain is a memory sponge. It contains a lifetime of memories that cause us to act or react based on inputs. Inputs come through our 5 senses. If you see and smell hot suya burning on the grill (inputs) you know how to react based on previous experiences (memory - " I HAVE TO EAT O!).
A set of miniaturized
circuits which represents the working memory of the computer. This
is where application programs (software) can be loaded from the outside
and then executed. The larger the RAM the better. For example a typical single
user computer system may contain approximately 1,000,000,000 bytes of
The computer's brain consists of the RAM and the CPU. The CPU and RAM work together as the computer's "brain". Each day when we start up the computer one of the first tasks will be to fill RAM with instructions to give it an ability to do work. This work may be in the creation of documents or tracking accounting data.
You control which instructions will go into the computer's brain. You control the sets of experiences you will provide the computer. Once in RAM, the computer will evaluate inputs from many devices and react. The most typical input device is a keyboard. As you type commands, the computer evaluates them. Based on the set of instructions within its RAM, it will follow some action: print a document, calculate, send information over a telephone line, etc.
At some later
point you may empty the computer's brain and install a different set
of instructions, thus giving it a different ability.
READ ONLY MEMORY (ROM)
This is a special section of memory that contains instructions which are activated each time the computer is turned on. These instructions are set at the factory and cannot be changed - thus, they can only be "read", not written to. ROM instructions perform equipment checks and initialization of the computer prior to each use. Furthermore, information on a ROM can not be altered or deleted.
However, new types of ROM (e.g DVD-RW, BD-RW etc.) can have some of the content on them edited, even deleted.
Think of disks as cassettes. You can record information on a cassette that can be replayed indefinitely and if desired, recorded over. Flash and Hard Disks operate in a similar fashion. We record (Save) data we have created - like a document - onto the disk. Then, hours, days, or months later we can play back (Retrieve) the document in the computer to alter or print out.
Storage devices are non-volatile in nature because they will retain their information without the use of electricity and can be grouped into any of the following: magnetic, solid state, optical.
Magnetic disks (made up of metals mostly) works in the same fashion but spins in a circle like a music record rather than moving in a straight line like recording tape - magnetic impressions are placed on the tape and can be later replayed. Hard disks are typical examples of magnetic storage.
Solid state disks are rather chip-like (mostly made of semiconductors and plastics) type of storage that have relatively smaller capacity(ies) than the magnetic storage. They are less likely to fail due to the nature of materials there are made of. Examples include flash drives, memory cards (SD/MiniSD/MicroSD/MMC/XD) etc.
Optical storage better grouped as ROM require a drive with a lens to write/read their content. They are made from plastics and can be any of CD (with 700MB capacity), DVD (with 4.7GB capacity; 9.4GB if it is a Double Layer) or Blu-Ray Disc with 25GB capacity; 50GB if it is Double Layer. Since optical disks have features of ROM, information stored on it is read only and can not be edited. However, some of their content on these discs can be edited and deleted when there are having the designation -RW (meaning rewritable).
When you format
a disk you ask the computer to inspect the magnetic surface of the
disk ( if it is a hard disk drive) for any errors, prepare it for use by future data and create
an index such as file allocation table (FAT) or new technology file system (NTFS) which is like a card
index for a large library of books. Formatting a disk is a little
like taking a blank piece of paper and using a pencil and ruler to
turn it into graph paper with both horizontal and vertical lines.
What was blank before now has little cells or file drawers which can
Since we have
covered data storage lets move to data input.
(b) SPECIALTY INPUT DEVICES
Another introductory topic is that of output devices such as a monitor, printer or plotter.
A plotter is a device which uses a motor to move pens or drawing implements in tightly controlled horizontal and vertical motions on a piece of paper or film. The computer can control a plotter to combine on one piece of paper differing pen colors and text and pictures stored within the computer. Computer plotter can be purchased with flat table or flat bed configurations or in models which move the pen(s) back and forth with gears that also drive the paper movement at the same time.
The printer is
probably the most common and useful output device attached to your
computer. There are many types of modern computer printer with differing
speeds and capabilities. The most common printer is the Dot
The laser and
ink jet printers are becoming more popular due to rapid speed of printing
and quiet mode of operation.
Dot matrix printers
are common and affordable alternatives for many small offices, home
computer hobbyists or organizations with voluminous printing requirements
(e.g. statements of accounts for banks). The Dot matrix is additionally
designed for use with continuous flow paper, as well as typical single
Connecting a printer
via a cable to the computer is always done through one of two plugs
(or interfaces) on the back of the computer. One type of interface
(computer plug) is serial, the other called parallel.
We have talked
about output to paper, next let's briefly discuss output to a monitor
or screen. The monitor is a television like device that the computer
uses to communicate with you. The monitor or video display works much
like your television - some older home computers still use a TV. An
old term for a monitor is the cathode ray tube or CRT. Monitors differ
in the sharpness or resolution they can display. On the low end of
the resolution spectrum is the monochrome (single color) monitor frequently
available in either green or amber screens. Next is the color RGB
monitor (RGB stands for Red, Green and Blue) which displays low resolution
color dots to make up an image.
Short for Modulator/Demodulator.
A device to send and receive computer output over telephone lines.
contains the most essential parts of the computer such as the CPU,
RAM, ROM, keyboard, speaker and power connections, and other assortment
of important parts.
TUTORIAL QUESTIONS (WHAT ARE COMPUTERS? (2))
1. RAM is usually
more powerful than ROM. COMMENT.
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