February 21, 2017

Computer Hardware Class #1

About Computer Hardware
In this post We will have an overview of a computer hardware which you will find much interesting as it  contains very amazing information about many hardware parts of the computer and their working,

Computer Systems.

Computer System consists of  Hardware and  Software.
Hardware : The physical components (electronic circuits) that make up the computer.
Software : The computer programms (Sequence of instructions) that tell the computer what to do in response to a command or some event.
In this chapter We'll take an introductry look at hardware.

The Components of A Computer

All computers, whatever their size or function, have certain basic components.They have input devices for reading data into main memory,a central processing unit (CPU) for processing the data, output devices for printing, displaying or outputting information, and auxiliary storage devices for permanent storage of programs and data.
Block Digram of a Computer
Block Digram of a Computer

Types of Computers.

  • MINI COMPUTERS : These are often used as a multi-user systems with hunderds of workstations or terminals attached to a central mini computer, For Example : EPOS (Electronic Point Of Sale) systems.
  • Mainframe Computers : They are used by large organizations suchas banks, Building societies,insurance companies , airlines and govermant departments.A main frame may have thousands of terminals attched to it at geographically remote locations, and occupy an entire site with hundreds of disk drives and other hardware units. Frequently ,the actual sitting of a Main Frame computer is kept secret to lessen the danger of a terrorist attack that may cause chaos to an organization.
  • SUPERCOMPUTERS : They are the largest catagery of computers, costing millions of pounds. They are mostly used by scientific and industrial reserch departments, goverments agencies such as NASA, the weather stock exchange and by very large commercial organizations. 

    The Processors.

The processor has the following functions:
  1. fetches the next instruction;
  2. decodes the instruction;
  3. executes the decoded instruction.
Most computers use intergrated circuits,or chips , for their processors and main memory. A chip is about 1cm square and can hold millions of electronic components such as transistors and resistors. The CPU of a microcomputer is called a microprocessor.The processor and main memory of a PC are commonly held on a single board called mother board.
In 1965 Gordon Moore predicted the capacity of a computer chip would double every year.He looked at the price and the performance ratios of the computer chips (the amount available at every 1$). over the previous three years and simply projected it farwards.He didn't really believe the rate of the improvement would last for long.but in fact to this day chip capacity is still doubling every 18 months or so.

Main Memory.

 The Program currently being executed and the data used by this program are held in main memory, which is divided into millions of indiviually addressable storage units called bytes.One Byte can hold one character ,or it can be used to hold a code representing , for example , a tiny part of a picture ,a sound , or part of computer program instruction.The total number of bytes in main memory is reffered to as the computer's memory size.Computer memory sizes are measured as follows:

  • 1 kiloByte (Kb) =  1024 bytes
  • 1 Megabyte (Mb) =   1024 Kb   = 1,048,576 bytes (about 1 million)
  • 1 Gigabyte (Gb) =    1024 Mb =    1,073,741,824 bytes (about 1 billion)
  • 1 Terabyte (Tb) =    1024 Gb =    1,099,511,627,776 bytes (about 1 trillion)
as with processing power the amount of memory that comes with standrad pc has increased exponentially over the past 20 years.In about 1980, BBC microcomputers with 32K of memory were bought in their thousands for home and school use. in 1981 , Bill gates of Microsoft made his famour remark "640K ought to be enough for every body".In 2004, a PC with 512Mb of main memory is standard , costing around 1,000 £ including bundled software.

RAM and ROM.

There are basically two kinds of main memory;  Ramdom Access Memory (RAM) which is the ordinary kind of main memory reffered above , used for storing programs which are currently running and data which is currently being processed.This type of memory is volatile which means that it loses all content on it as soon as the machine is switched off.
Read Only Memory (ROM) is other type of main memory , and this is non-volatile , with its contents permanently etched to the memory chip at the manafacturing stage. It is used for example to hold the  Bootstrap Loader, the program which runs as soon as the computer is switched on and instructs it to load the data from the disk into main memory RAM. It may also store fixed data associated with the computer system. In special purpose computers used in video recorders, Washing machines and cars, the program instruct and stored in ROM.

Cache Memory.

Cache memory is a type of very fast memory that is used to improve speed of a computer , doubling it in some cases . It acts as an intermediate store between the CPU and main memory.and works by storing the most frequently or recently used instructions and data so that it will be very fast to retrive again.Thus when an item of data is required ,a whole block of data will be read into cache in the expectation that the next piece of data required is likely to be in the same block.The amount of cache memory is generally between 1Kb and 512 Kb.
Cache Memory Block Digram
Cache Memory Block Digram

Disk Storage.

The most common form of zuxiliary storage (also known as external or secondry memory or backing store) is disk. All standalone PCs dome eqquipped with an in inbuilt hard disk. the capacity of which is also measured in bytes. A typical hard disk for a PC stores several Gigabytes , and is used for storing softwares including the operating systems,other system softwares , application programms and data for long term storage.
Floppy disk consist of a thin sheet of mylar plastic encased in a head 3 1/3" casing. The standrad type of floppy disc holds about 1.44 MB. while flash devices can hold upto 500GBs.
Hard Disk Explanation

Floppy Drive Explanation

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