Computers

Posted by on Oct 14 2008 |

Hardware and Software

    Computers are made up of hardware and software.  Hardware is the tangible, physical equipment that can be seen and touched.  Examples of hardware are things such as the keyboard, printer, monitor, and computer chips.

    Software is the intangible instructions that tell the computer what to do.  Software is things such as Word, iMovie, PowerPoint, Windows XP, Sim City, or Oregon Trail.  Software is a set of instructions that tell a computer how to perform a task.  People who write software are called programmers.

    Programmers write instructions, or programs, to the computer so that it is able to execute a task and operate properly.  A program can be defined as a series of detailed step-by-step instructions that tell the computer precisely what actions to perform.

 

Many people believe that computers can do just about anything and that their level of sophistication requires a genius to program and run them.  In reality, computers are very simple devices that can perform only four basic functions.  A computer can (1) store data and programs, (2) function unattended due to its ability to interpret and follow instructions it is provided, (3) do arithmetic calculations, and (4) perform logical comparisons.  What makes the computer such a powerful device, given only these four basic functions, is its tremendous speed, its accuracy, and its ability to store vast volumes of data.

 

Memory – Chips (internal) – CD (external)

    The computer must be given instructions, in the form of software, which tell it exactly what to do.  The instructions that the computer follows are stored in locations known as memory.  For simplicity purposes think of memory in two categories:
(1) The computer’s Internal memory (ex. microchips)
(2) The computer’s External memory (ex. diskettes & hard drives)

    The computer’s internal memory which is composed of computer chips is divided into two types:  RAM (random-access memory) and ROM (read-only memory).  RAM’s primary purpose is to temporarily store programs given to it by a programmer or operator of the computer.  This type of memory is temporary because it is erased when the computer is turned off (powered down).  In other words, all the information in RAM is erased when the computer is turned off.  It is called random access because the processor can jump directly form one location to another in random order as the program is needed.  RAM holds programs such as Microsoft Office XP, MicroType, Internet Explorer or whatever program the computer is running.

    ROM’s primary purpose is to store important instructions that the computer will reuse over and over such as what to do when the computer is turned on and how to control specific requests made by the computer.  ROM is permanent memory that can not be changed or erased.  This is why it is called Read-Only Memory.

Input and Output devices

    A hardware device which enables the computer to accept data is called an input device.  The most common example of an input device is a keyboard.  Other commonly known input devices include a mouse, bar-code scanner, light pen, touch screens, and speech recognition devices.

    A hardware device which reports the information in a form we can understand is called an output device.  The two most common forms of output devices are monitors, printers, and speakers

Processors
    All computers do processing by following a set of instructions in a software program.  The computer chip that receives and carries out these instructions is called the processor.  All computer systems, regardless of size or manufacturer, have processors.

    The processor performs many different functions.  It receives and temporarily stores instructions as well as the data to be processed.  It moves and changes stored data.  It does arithmetic calculations.  It makes decisions of logic, such as determining if two numbers are equal.  It directs the action of the input and output devices.   The CPU is often referred to as the brains of the computer system.

External Storage

    Nearly all general-purpose computers include the ability to connect to additional storage devices that hold data outside the memory of the computer.  These additional storage devices are known as external storage.  External storage devices are on-line to the computer; that is, they are connected directly to the computer.  They are, therefore, under the control of the processor and can be used at all times.  The most common form of external storage is a thumb drive (aka… USB flash drive).    Other forms of external storage include hard drives and CD/DVD (recordable) drives.

A flash drive can hold between 128 MB (megabytes) to 64 GB (gigabytes) of memory where one CD can store 700 MB (megabyte).  A single layer DVD can hold 4.7 GB (gigabytes of memory).  Hard drives can hold even more.  Most hard drives hold between 20 GB (gigabytes) to 1000 GB (or 1 terabyte).

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