What is Computer and it's Components

Computer:

   "The term computer is basically taken from the word “compute”. A computer is an electronic device as we know that takes  

COMPUTER

data and instructions as an input from the operator, processes the data according to set of instructions (called program) and provides useful information known as output. A collection of related program is referred to as the software. The physical circuitry and components are known as the hardware." 

 Hardware can be categorized in five blocks :

               (i) Input Unit
            (ii)Arithmetic Logic Unit

            (iii) Control Unit

            (iv) Memory
            (v) Output Unit

 Components of Computer

Block Diagram of Computer
                                                                                                               

Input Unit :-

                      This unit contains devices with the help of which user enter data into computer. This unit makes link  between user and computer. The data read from the computer                                                    

device is stored in the computer’s memory  .They are used for accepting thedata on which the operation are to be performed the most commonly used input devices among other are;
       a) Keyboards
b) Mouse
c) Scanner
            d)Digital camera
  e) Joy sticks
 Computer peripherals are any computer components that expand system functionality and are not necessary for basic operation ( not the part of CPU).

 CPU (Central Processing Unit)

 ALU(Arithmetic Logic Unit):-

The ALU performs arithmetic and logical operations .the arithmetic operations 

include addition, subtraction,  multiplication and division. Numerical data in the form of integers are supported by all the computers. Some computers also support floating point numbers. Logical operations always include the Boolean functions such as AND, OR and NOT. These operations used during conditional branching.

 Control Unit (CU):-

     A computer control unit is a part of the computer processor. The control unit fetches 

  internal instructions of programs from the main memory to the processor the control unit coordinates the activities of the various component of the computer. The arithmetic logic unit and the control unit together comprise the Central Processing Unit (CPU) Control unit controls flow of data: 

    a. From input device to memory
                               b. From memory to output device or secondary storage
                c. From secondary storage to memory
d. From ALU to memory
e. From memory to ALU

Memory Unit:-

           The information(instruction and data) requirement is stored in memory . The computer’s memory is constructed out of semi-conductor material and stores information in binary form. The memory is organized into equal sized units(usually collection of 8 bits, called a byte) these units are arranged in a sequence and are identified by numbers called addresses.

Output Unit:-

                  Just as input devices are used to give the data to computer, there should be some

    means for the computer to  communicate with the user. The data generated by the computer is displayed using an output device. Examples of output devices are Monitors, printer, card punch etc. 

Classification of Computer Memory:-

    • Registers:-  Registers are location within the CPU where data stored temporarily during processing. Registers(high speed )are used in arithmetic and logic operations for holding data operands. Some registers can access by the user through instructions. Others are reserved for the use of the CPU to perform it’s activities.
 • Cache Memory:- Cache memory is a very high speed memory which speeds up the 

                                         CPU working. It acts as a buffer between CPU and a main memory. The regularly used data's and program files which  are used by CPU are stored in the Cache memory. CPU can access the data when ever required.  In the starting, Operating system starts it transfer some important files and data from disk to cache memory which CPU can access easily.

 Primary Memory (Main Memory)

 There are two kinds of primary Memory:-

 RAM –  Random Access Memory (this is used for storing programs that are currently 

              working and data that is being processed) Main      Memory   Stores info about applications that are open.    VOLATILE –When you switch off the machine, all the data will disappears!!!








ROM –  Read Only Memory (its contents are PERMANENTLY fixed into the memory chip 

          at the manufacturing stage. It is used –for example –to load the bootstrap loader (the program that loads as soon as you start the computer) Non-Volatile (does not change) Programs that are necessary for the computer(machine) to run Boot up program etc.

 Secondary Memory

         This memory is also known as external memory. It is slower than main memory. It

is used for storing  data and Information permanently on it. CPU(central processing unit) access the data of secondary  memory by some input-output routines. Contents of secondary memories are first transferred to main memory, and then CPU(central processing unit)  can access it. Example of secondary memory: DVD , disk, CD-ROM(Read Only Memory) etc.

In above figure(MEMORY HIERARCHY DIAGRAM) various types of memory are shown in the order of increasing size, decreasing speed and decreasing cost. 

  The capacity and size of memory of a computer is measured in terms of the number of bytes associated with it. Each one of the digits 0 and 1 of the binary system is called 1 bit. 
The following units are used to measure storage capacity of the storage unit.. 
                                    
1 Bit = Binary Digit (single 1 or 0) 
4 Bit = Nibble 
 8 Bits = 1 Byte B 
  1024 Bytes = 1 Kilobyte KB 
1024 Kilobytes = 1 Megabyte MB
1024 Megabytes = 1 Gigabyte GB
 1024 Gigabytes = 1 Terabyte TB
 1024 Terabytes = 1 Petabyte PB
 1024 Petabytes = 1 Exabyte EB
 1024 Exabytes = 1 Zettabyte ZB 
1024 Zettabytes = 1 Yottabyte YB 
    1024 Yottabytes = 1 Brontobyte BB 
1024 Brontobytes = 1 Geopbyte