BASIC STRUCTURE OF COMPUTERS: 




Computer Organization

It refers to the operational units and their interconnections that realize the architectural specifications. 

It describes the function of and design of the various units of digital computer that store and process information. 

Computer hardware: 

Consists of electronic circuits, displays, magnetic and optical storage media, electromechanical equipment and communication facilities. 


Computer Architecture: It is concerned with the structure and behaviour of the computer. It includes the information formats, the instruction set and techniques for addressing memory. 

 Functional Units -A computer consists of 5 main parts. Input Memory Arithmetic and logic Output Control Units


Input unit accepts coded information from human operators, from
electromechanical devices such as keyboards, or from other computers
over digital communication lines.
The information received is either stored in the computers memory for
later reference or immediately used by the arithmetic and logic circuitry to
perform the desired operations.
The processing steps are determined by a program stored in the memory.
Finally the results are sent back to the outside world through the output
unit.
-All of these actions are coordinated by the control unit.
-The list of instructions that performs a task is called a program.
-Usually the program is stored in the memory.
-The processor then fetches the instruction that make up the program from
-the memory one after another and performs the desire operations.


1.1 Input Unit:
 Computers accept coded information through input units, which read the
data.
 Whenever a key is pressed, the corresponding letter or digit is
automatically translated into its corresponding binary code and transmitted
over a cable to either the memory or the processor.


Some input devices are
 Joysticks
 Trackballs
 Mouses
 Microphones (Capture audio input and it is sampled & it is
converted into digital codes for storage and processing).


1.2.Memory Unit:
It stores the programs and data.
There are 2 types of storage classes
 Primary
 Secondary


Primary Storage:
It is a fast memory that operates at electronic speeds.
Programs must be stored in the memory while they are
being executed.
The memory contains large no of semiconductor storage
cells.
Each cell carries 1 bit of information.
The Cells are processed in a group of fixed size called
Words.
To provide easy access to any word in a memory,a distinct
address is associated with each word location.
Addresses are numbers that identify successive locations.
The number of bits in each word is called the word length.
The word length ranges from 16 to 64 bits.


There are 3 types of memory.They are
 RAM(Random Access Memory)
 Cache memory
 Main Memory


RAM:
Memory in which any location can be reached in short and fixed amount of time
after specifying its address is called RAM.


Time required to access 1 word is called Memory Access Time.
Cache Memory:
The small,fast,RAM units are called Cache. They are tightly coupled with processor to achieve high performance.