Saturday, 9 June 2018

What Is Digital Computer And What Are The Type Of Digital Computer??

What Is Digital Computer And What Are The Type Of Digital Computer??

What Is The Digital Computer System And How Its A Works And Which Is The Different Types Of Digital Computers And Major Parts Of Digital Computer!!

The Digital Computer is a system of hardware that performs arithmetic operations, manipulates data (usually in binary form) and makes decision .

Even thought human beings can do most of the things which a computer can do, the computer does the things with much greater speed and accuracy .

The Digital Computer, however, has to be given a complete set of instructions that tell it exactly what to do at each step of its operation This set of instructions is called a program.

Programs are placed in the computer's memory unit in binary coded form with each instruction having a unique code.

The computer takes these instruction codes from memory one at a time and performs the operation called for by the code .

Major Parts of a Digital Computer 

There are several types of computer systems, but each can be broken down into the same functional units.

Each unit performs specific functions, and all the units function together to carry out the instructions given in the program. 


shows the five major functional units of the digital computer and their interconnections.

The solid lines with arrows represent the flow of information The dashed lines with arrows represent the flow of timing and control signals.

The major functions of each unit are described below 

  • Input unit: Through this unit, a complete set of instructions and data is fed into the memory unit to be stored there until needed. The information typically enters the input unit by means of a magnetic tape, or a keyboard.

Memory unit: In addition to the instructions and data received from the input unit, the memory stores the Results of arithmetic and logic operations received from the arithmetic and logic unit. 

also supplies information to the output unit.  

Control unit: This unit takes instructions from the memory unit one at them.

It then sends the be executed. 

a time and interprets appropriate signals to all the other units to cause the specific instruction to be executed.

Arithmetic and logic unit: All arithmetic calculations and logical decisions are performed in this unit. 

It then sends the results to the memory unit to be stored there.

Output unit: This unit takes data from the memory unit and prints out, displays or otherwise presents information to the operator 


The number of computer types depends on the criteria used to classify them.

Computers differ in their physical size, operating speed, memory capacity and processing capability as well as in respect of other characteristics.

The most common way to classify computers is by their physical size, which usually but not always is indicative of their relative capabilities.

The three basic classifications are: microcomputer, minicomputer, and mainframe. 

the smallest type of computer. It generally consists of several IC cluding a microprocessor chip, memory chips, and input-output interface chips along

 The microcomputer is with input-output devices such as a keyboard and video display. Microcomputers resul the tremendous advances in IC fabrication technology that has made it possible to pack more and more  system. circuitry into a small space.

Figure shows block diagram of the microcomputer

Minicomputers are larger than microcomputers and are widely used in industrial control systems, research laboratories, etc.

They are generally faster and possess more processing capabilities than microcomputers. 

Mainframes are the largest computers. These maxicomputers include complete systems of peripheral equipment such as magnetic tape units, magnetic disk units, card punchers and readers (now obsolete), keyboards, printers and many more.

Applications of mainframes range from computation-oriented science and engineering problem-solving to data-oriented business applications, where emphasis is on monitoring and updating of large quantities of data and information

Thursday, 7 June 2018

What Is The Microprocessor And Do Its Work??

What Is The Microprocessor And Do Its Work??

Basic Of The Microprocessor And Functions Of Microprocessor And A Microprocessor Based System Theory !!

The Microprocessor is a Programmable Device that Takes in NumbersPerforms on Them  Arithmetic or Logical Operations according to  the Program Stored in Memory and then Produces other numbers as a result.


• Lets expand each of the underlined words:

– Programmable Device: 

The Microprocessor can perform
different sets of operations on the data it receives depending on the sequence of instructions supplied in the given
program. By changing the program, the Microprocessor manipulates  the data in different ways.

– Instructions: Each Microprocessor is designed to execute a specific group of operations. This group of operations is
called an instruction set. This instruction set defines what the  Microprocessor can and cannot do.

– Takes in: 

The data that the Microprocessor
manipulates must come from somewhere.
• It comes from what is called “input devices”.
• These are devices that bring data into the system from the outside world.
• These represent devices such as a keyboard, a  mouse, switches, and the like.

– Numbers:

 The Microprocessor has a very narrow view on life. It only understands binary numbers. A binary digit is called a bit (which comes from binary digit).  The microprocessor recognizes and processes a group of bits together. This group of bits is called a “word”. The number of bits in a Microprocessor’s word, is a measure of its

– Words, Bytes, etc.

• The earliest Microprocessor (the Intel 8088 and Motorola’s 6800) recognized 8-bit words.
– They processed information 8-bits at a time. That’s why they are called “8-bit processors”. They can handle large numbers, but in order to process these numbers, they broke them into 8-bit pieces
and processed each group of 8-bits separately.
• Later Microprocessors (8086 and 68000) were designed with
16-bit words.
– A group of 8-bits were referred to as a “half-word” or “byte”.
– A group of 4 bits is called a “nibble”.
– Also, 32 bit groups were given the name “long word”.
• Today, all processors manipulate at least 32 bits at a time and
there exists microprocessors that can process 64, 80, 128 bits .

– Arithmetic and Logic Operations: 

• Every Microprocessor has arithmetic operations such as add and subtract as part of its instruction set.
– Most Microprocessors will have operations such as multiply and
– Some of the newer ones will have complex operations such as  square root.
• In addition, Microprocessors have logic operations as well.  Such as AND, OR, XOR, shift left, shift right, etc.
• Again, the number and types of operations define the Microprocessor’s instruction set and depends on the specific microprocessor.

– Stored in memory :

• First, what is memory?

– Memory is the location where information is kept while not in  current use.
– Memory is a collection of storage devices. Usually, each storage  device holds one bit. Also, in most kinds of memory, these
storage devices are grouped into groups of 8. These 8 storage  locations can only be accessed together. So, one can only read or
write in terms of bytes to and form memory.
– Memory is usually measured by the number of bytes it can hold.  It is measured in Kilos, Megas and lately Gigas. A Kilo in
computer language is 210 =1024. So, a KB (KiloByte) is 1024  bytes. Mega is 1024 Kilos and Giga is 1024 Mega.

– Stored in memory:

• When a program is entered into a computer, it is  stored in memory. Then as the microprocessor starts to execute the instructions, it brings the instructions
from memory one at a time.
• Memory is also used to hold the data.
– The microprocessor reads (brings in) the data from memory when it needs it and writes (stores) the results into memory when it is done.

– Produces:

 For the user to see the result of the execution of the program, the results must be  presented in a human readable form.
• The results must be presented on an output device.
• This can be the monitor, a paper from the printer, a

simple LED or many other forms.

A Microprocessor - based system


From the above description, we can draw the  following block diagram to represent a
microprocessor-based system:

Inside The Microprocessor

• Internally, the microprocessor is made up of  3 main units.
– The Arithmetic/Logic Unit (ALU)
– The Control Unit.
– An array of registers for holding data while it is  being manipulated.

Organization of a Microprocessor -
based system

Let’s expand the picture a bit.

Sunday, 3 June 2018

Memory - How To Works A Microprocessors Memory Stored System!!

Memory - Microprocessors Memory Stored System!!! 

Memory Storage System In Microprocessor And The Execute Program System

• Memory stores information such as instructions  and data in binary format
 (0 and 1). It provides this information to the microprocessor whenever  it is needed.
• Usually, there is a memory “sub-system” in a Microprocessor -based system. This sub-system includes:
– The registers inside the Microprocessor
– Read Only Memory (ROM)

• used to store information that does not change.
– Random Access Memory (RAM) (also known as Read/Write Memory).
• used to store information supplied by the user. Such as programs and data.

Memory Map and Addresses

• The Memory map is a picture representation of the address range and shows where the different memory chips are located within the address range.


• To execute a program:

– the user enters its instructions in binary format into the memory.
– The Microprocessor then reads these instructions and  whatever data is needed from memory, executes the instructions and places the results either in Memory or
produces it on an output device.

The three cycle instruction 
execution model

• To execute a program, the Microprocessor “reads” each instruction from Memory, “interprets” it, then  “executes” it.
• To use the right names for the cycles:
– The Microprocessor fetches each instruction,
– decodes it,
– Then executes it.

• This sequence is continued until all instructions are performed.