Number Systems

Two types of number systems are:

•  Non-positional number systems
•  Positional number systems         

                               

•  Non-positional number systems

• Characteristics 

 Use symbols such as I for 1, II for 2, III for 3, IIII for 4, IIIII for 5, etc. 

Each symbol represents the same value regardless of its position in the number .

 The symbols are simply added to find out the value of a particular number.

•  Difficulty 

 It is difficult to perform arithmetic with such a number system 

• Positional Number Systems 

              Characteristics

 Use only a few symbols called digits

These symbols represent different values depending on the position they occupy in the number

 The value of each digit is determined by: 

1. The digit itself 

2. The position of the digit in the number 

3. The base of the number system

(base = total number of digits in the number system) 

 The maximum value of a single digit is always equal to one less than the value of the base.

• Decimal Number System

              Characteristics 

1.  A positional number system 
2. Has 10 symbols or digits (0, 1, 2, 3, 4, 5, 6, 7, 8,  9).  Hence, its base = 10 
3. The maximum value of a single digit is 9 (one less than the value of the base) 
4. Each position of a digit represents a specific power of the base (10) 
5. We use this number system in our day-to-day life

Example

258610 = (2 x 103) + (5 x 102) + (8 x 101) + (6 x 100)

= 2000 + 500 + 80 + 6

• Binary Number System

 Characteristics 

1.  A positional number system 
2.  Has only 2 symbols or digits (0 and 1).  Hence its base = 2 
3.  The maximum value of a single digit is 1 (one less than the value of the base) 
4.  Each position of a digit represents a specific power of the base (2) 
5.  This number system is used in computers

Example

101012 = (1 x 24) + (0 x 23) + (1 x 22) + (0 x 21) x (1 x 20) = 16 + 0 + 4 + 0 + 1 =  2110

• Octal Number System 

Characteristics

1.  A positional number system 
2.  Has total 8 symbols or digits (0, 1, 2, 3, 4, 5, 6, 7).  Hence, its base = 8 
3.  The maximum value of a single digit is 7 (one less than the value of the base 
4.  Each position of a digit represents a specific power of the base (8)
5.  Since there are only 8 digits, 3 bits (23 = 8) are sufficient to represent any octal number in binary   

Example
20578   = (2 x 83) + (0 x 82) + (5 x 81) + (7 x 80)
= 1024 + 0 + 40 + 7
 =  107110

• Hexadecimal Number System 

Characteristics

1.  A positional number system 
2.  Has total 16 symbols or digits (0, 1, 2, 3, 4, 5, 6, 7, 8, 9, A, B, C, D, E, F).  Hence its base = 16
3.  The symbols A, B, C, D, E and F represent the decimal values 10, 11, 12, 13, 14 and 15 respectively 
4.  The maximum value of a single digit is 15 (one less than the value of the base)
5.  Each position of a digit represents a specific power of the base (16) 
6.  Since there are only 16 digits, 4 bits (24 = 16) are sufficient to represent any hexadecimal number in binary

Example
 1AF16 =  (1 x 162) + (A x 161) + (F x 160)
 =  1 x 256 + 10 x 16 + 15 x 1
=  256 + 160 + 15
 =  43110

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Basic Organization of a Computer System

Input:

1. It accepts (or reads) instructions and data from outside world 

2. It converts these instructions and data in computer acceptable form 

3. It supplies the converted instructions and data to the computer system for further processing

Output Unit:

1. It accepts the results produced by the computer, which are in coded form and hence, cannot be easily understood by us 

2. It converts these coded results to human acceptable (readable) form 

3. It supplies the converted results to outside world

Storage Unit:

1. Data and instructions required for processing (received from input devices) 

2. Intermediate results of processing 

3. Final results of processing, before they are released to an output device

                 

                             Two Types of Storage 

•  Primary storage
• Secondary storage 

 Primary storage:

Used to hold running program instructions 

 Used to hold data, intermediate results, and results of ongoing processing of job(s) 

 Fast in operation 

 Small Capacity 

 Expensive 

 Volatile (looses data on power dissipation)

 Secondary storage

Used to hold stored program instructions 

 Used to hold data and information of stored jobs 

 Slower than primary storage 

 Large Capacity 

 Lot cheaper that primary storage 

 Retains data even without power

Arithmetic Logic Unit (ALU) 

Arithmetic Logic Unit of a computer system is the place where the actual executions of instructions takes place during processing operation.

Control Unit (CU) 

Control Unit of a computer system manages and coordinates the operations of all other components of the computer system.

Central Processing Unit (CPU) 

It is the brain of a computer system.

It is responsible for controlling the operations of all other units of a computer system.

The System Concept  

A system has following three characteristics:

 A system has more than one element. 

2. All elements of a system are logically related/

 3. All elements of a system are controlled in a manner to achieve the system goal.

A computer is a system as it comprises of integrated components (input unit, output unit, storage unit, and CPU) that work together to perform the steps called for in the executing program

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Five basic operations of a computer

 Inputting:
The process of entering data and instructions into the computer system
 Storing:
 Saving data and instructions to make them readily available for initial or additional processing whenever required
 Processing:
 Performing arithmetic operations (add, subtract, multiply, divide, etc.) or logical operations (comparisons like equal to, less than, greater than, etc.) on data to convert them into useful information
Outputting:
The process of producing useful information or results for the user such as a printed report or visual display
Controlling:
Directing the manner and sequence in which all of the above operations are performed

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Generations of computer

·         “Generation”in computer talk is a step in technology.  It provides a framework for the growth of computer industry

·         Originally it was used to distinguish between various hardware technologies, but now it has been extended to include both hardware and software

·         Till today, there are five computer generations

Generation       (Period)	Hardware Technology	Software Technology	Characteristics	Some representative System
First (1942-1955)	Vacuum tubes         Electromagnetic relay memory           Punched cards secondary storage	Machine and assembly languages           Stored program concept          Mostly scientific applications	Bulky in size          Highly unreliable          Limited commercial use and costly          Difficult commercial production          Difficult to use	·        ENIAC ·         EDVAC ·          EDSAC ·         UNIVAC I ·          IBM 701
Second (1955-1964)	Transistors   Magnetic cores memory   Magnetic tapes   Disks for secondary storage	Batch operating system   High-level programming languages   Scientific and commercial applications	Faster, smaller, more reliable and easier to program than previous generation systems   Commercial production was still difficult and costly	Honeywell 400   IBM 7030   CDC 1604  UNIVAC LARC
Third (1964-1975	ICs with SSI and MSI technologies   Larger magnetic cores memory  Larger capacity disks and magnetic tapes secondary storage   Minicomputers; upward compatible family of computers	Timesharing operating system  Standardization of high-level programming languages  Unbundling of software from hardware	Faster, smaller, more reliable, easier and cheaper to produce   Commercially, easier to use, and easier to upgrade than previous generation systems   Scientific, commercial and interactive on- line applications	IBM 360/370   PDP-8   PDP-11   CDC 6600
Fourth (1975-1989)	ICs with VLSI technology  Microprocessors; semiconductor memory   Larger capacity hard disks as in-built secondary storage  Magnetic tapes and floppy disks as portable storage media   Personal computers   Supercomputers based on parallel vector processing and symmetric multiprocessing technologies § Spread of high-speed computer networks	Operating systems for PCs with GUI and multiple windows on a single terminal screen   Multiprocessing OS with  concurrent programming languages   UNIX operating system with C programming language   Object-oriented design and programming   PC, Network-based, and super-computing applications	Small, affordable, reliable, and easy to use PCs   More powerful and reliable mainframe systems and supercomputers   Totally general purpose machines  Easier to produce commercially   Easier to upgrade   Rapid software development possible	IBM PC and its clones   Apple II  TRS-80   VAX 9000   CRAY-1   CRAY-2  CRAY-X/M
Fifth (1989- Present)	ICs with ULSI technology   Larger capacity main memory, hard disks with RAID support   Optical disks as portable read-only storage media   Notebooks, powerful desktop PCs and workstations   Powerful servers,  supercomputers   Internet   Cluster computing	Micro-kernel based, multithreading, distributed OS   Parallel programming libraries like MPI & PVM   JAVA   World Wide Web   Multimedia, Internet applications   More complex supercomputing applications	Portable computers   Powerful, cheaper, reliable, and easier to use desktop machines   Powerful supercomputers   High uptime due to hot-pluggable components  Totally general purpose machines   Easier to produce commercially, easier to upgrade   Rapid software development possible	IBM notebooks   Pentium PCs   SUN Workstations   IBM SP/2   SGI Origin 2000   PARAM 10000

First Generation Computer

Second Generation Computer

Third Generation Computer

Fourth Generation Computer

Five Generation Super computer

Five Generation Robot

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Evolution of computer & Some of earlier computer's

                   Evolution of Computers

·         Blaise Pascal invented the first mechanical adding machine in 1642

·         Baron Gottfried Wilhelm von Leibniz invented the first calculator for multiplication in 1671

·         Keyboard machines originated in the United States around 1880

·         Around 1880, Herman Hollerith came up with the concept of punched cards that were extensively used as input media until late 1970s

·         Charles Babbage is considered to be the father of modern digital computers

·          He designed “Difference Engine “in 1822

·          He designed a fully automatic analytical engine in 1842 for performing basic arithmetic functions

·          His efforts established a number of principles that are fundamental to the design of any digital computer

Some of well known earlier computers

·          The Mark I Computer (1937-44)

·         The Atanasoff-Berry Computer (1939-42)

·          The ENIAC (1943-46) § The EDVAC (1946-52)

·          The EDSAC (1947-49)

·          Manchester Mark I (1948)

·          The UNIVAC I (1951)

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Characteristics of computer

                                    Characteristics of computer

1) Automatic: Given a job, computer can work on it automatically without human interventions.

2) Speed: Computer can perform data processing jobs very fast, usually measured in microseconds (10-6), nanoseconds (10-9), and picoseconds (10-12).

3) Accuracy: Accuracy of a computer is consistently high and the degree of its accuracy depends upon its design. Computer errors caused due to incorrect input data or unreliable programs are often referred to as Garbage- In-Garbage-Out (GIGO).

4) Diligence: Computer is free from monotony, tiredness, and lack of concentration. It can continuously work for hours without creating any error and without grumbling.

5) Versatility: Computer is capable of performing almost any task, if the task can be reduced to a finite series of logical steps.

6) Power of Remembering: Computer can store and recall any amount of information because of its secondary storage capability. It forgets or looses certain information only when it is asked to do so.

7) No I.Q.: A computer does only what it is programmed to do. It cannot take its own decision in this regard.

8) No Feelings: Computers are devoid of emotions. Their judgments based on the instructions given to them in the form of programs that are written by us (human beings).

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Data processing

Data Processing

The activity of processing data using a computer is called data processing

·         Data

·         Capture Data

·         Manipulate Data

·         Output Results

·         Information

Data is raw material used as input and information is processed data obtained as output of data processing.

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What is Computer?

The word computer comes from the word “compute”, which means, “to calculate”

 Thereby, a computer is an electronic device that can perform arithmetic operations at high speed

 A computer is also called a data processor because it can store, process, and retrieve data whenever desired

or 

Computer is an electronic device which help human do do work fast and aquatically. 

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