Computer Basics

Definition of Computer :
     A computer is a electronic device that accepts information in the form of digital data (format like: 010101), processing this digitalized data and manipulates it and generates some result based on a program or sequence of instructions. And Finally gives the user a meaningful information in the form of data. For understanding the concept of a computer system, it can be divided to two main parts :-


1. Hardware :
     All the physical components which are visible to a user and connected to a computer via cable or some medium (eg. ethernet, bluetooth) is called hardware. User's can touch a hardware component. Some essential hardware is Central Processing Unit, Monitor, Keyboard, Mouse, Printer, Audio Device etc.

2. Software :
     Basically, The Software is a collection of programs. Programs are some executable code, which is a form of data. Software is the medium of instructing hardwares to work. (eg. MS-Office, Media-player etc.)

***Software is a vast topic, so it will be discuss later.***

A Description About Hardware :
     Basically, the term Hardware as we understand that a computer has CPU (Central Processing Unit), Monitor, Keyboard, Mouse etc. Those components are definitely a hardware component and falls into hardware. But in case of educational concept they are included in the different units of computer architecture. Those are as follows:

(a)Input unit:  Input unit is the medium through which we can communicate with the computer. We send information to a computer via input unit (eg. Mouse, Keyboard etc).
(b)Output unit :  Output unit is the medium by which we get the processed result. (eg. Monitor, Printer etc).
(c)ALU (Arithmetical and logic unit) :  Arithmetic and Logic unit is responsible for arithmetical and logical action done by the system. This unit processes the data, manipulates it and gives the result. It is a hardware level concept but not hardware part.
(d)Control unit :  Control unit is responsible for controlling the signal to all the other units in order to maintain the integrity inside the computer system. As ALU it is also hardware level concept but not a part.
(e)Memory :  Memory is the media where we can store information and retrieve it. Basically it is divided to two parts.

                                         (a) Primary Memory
                                         (b) Secondary Memory
(a)Primary Memory:
Primary memory is the main memory of the computer system. It is works fast but costly as made up of semi-conductor devices. There are two parts of main memory.
                                         (i) ROM
                                         (ii) RAM
(i) ROM (Read Only Memory ) :
      As its name signifies, we can only read the contents of ROM but we cannot write over it. We cannot modify the contents of ROM or we cannot add more information in ROM because the programs of a ROM are stored permanently at the time of manufacturing by the system programmers. So the programs written in ROM or are permanent and they can't be changed during the life time. All the memory locations are occupied by the program and can't overwrite it. As the concept of memory comes so let me define the address of a memory. Memory addressing concept is like the page number of a book and all the memory space are divided applying the unit of byte system like 1 byte, 2 byte, 3 byte or 4 byte depending upon the system. Addressing of memory done by as follows:
                                         1 Byte = 8 bit
                                         1024 Byte = 1KB [Kilo Byte]
                                         1024 KB = 1 MB [Mega Byte]
                                         1024 MB = 1 GB [Giga Byte]

(ii) RAM (Random Access Memory) :
      It is called RAM since we can randomly access any location of the memory. RAM is RWM (Read Write Memory) since we can read it contents as well as write over the locations of this memory. As this memory is addressable as byte size and using which we can access the content of that location. RAM is volatile that is as soon as the power supply goes off; all the contents of this memory are get destroyed.

(b)Secondary Memory:
     Secondary memory is the permanent storage of a computer. Generally it is made up of magnetic material. It is slow and comparatively cheap memory. It can hold data for a long period. For example when writing some word in a notepad is the contents are loaded in the RAM and when save the content it is stored in the secondary memory. Time to time we will have to transfer the contents of RAM to Secondary Memory in order to store them permanently. (e.g. floppy disk, Hard disk, Magnetic Tape, Magnetic disk, CD etc).

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