FCH 1: Fundamental of Computer
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1. Digital Logic Function and Boolean Algebra
A Boolean expression is a string of symbols representing local variables and logical
operations which is evaluated to give a logical value.
E.g: A + A’B
A Logic function is an expression expressed algebraically with binary variables, logical
operation symbols, parenthesis and equal sign, is also known as Boolean function.
Eg: If logic function is R = A + B, then there value must be in 0 and 1.
Boolean algebra is the branch of mathematics that includes methods for manipulating
logical variables and logical expressions.
Eg: Logical values: True (T) or False (F)
Representation: ON (1) or OFF (0)
1.1. Basic Logical//Boolean Operation
An Operation is special symbol that indicates the operation to be carried out
between two operands.
1.1.1. AND Operation
AND Operation is logical multiplication which is denoted by (.) operator. It
generate TRUE if all the inputs are TRUE, otherwise FALSE.
Input Output
A B R=A.B
T T T
T F F F T F
F F F
1.1.2. OR Operation
OR Operation is logical addition which is denoted by (+) operator. It generates
TRUE if any one input is TRUE otherwise FALSE.
Input Output A B R=A+B
T T T T F T
F T T F F F
1.1.3. NOT Operation
NOT Operation is logical complement which is denoted by (`) operator or bar().
It generate TRUE if the input is FALSE, otherwise FALSE output.
Input Output
A B=A` T F
F T
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1.2. Truth Table
A Truth Table is the tabular representation of Boolean function used in logic to
compute the functional values of logical expression on each of their functional
arguments.
1.3. Logic Gates
A Logic Gate is an electronic circuit which generates only one output signal from one
or more input signals.
1.3.1. AND Gate
AND Gate is an electronic circuit which is used to perform logical multiplication.
It is denoted by (.). It generate 1 or TRUE or ON output if all the inputs are 1 or
TRUE or ON otherwise 0 or FALSE or OFF output.
Algebraic Expression: R=A.B
Graphical Symbols
A
R=A.B
B
1.3.2. OR Gate
OR Gate is an electronic circuit which is used to perform logical addition. It is
denoted by (+). It generate 1 or TRUE or ON output if at least one the input is 1
or TRUE or ON otherwise 0 or FALSE or OFF output.
Algebraic Expression: R=A+B
Graphical Symbols
A
R=A+B
B
1.3.3. NOT Gate
NOT Gate is an electronic circuit which is used to perform logical complement.
It is denoted by (` or ¯). It generate 1 or TRUE or ON output if the input 0 or
FALSE or OFF otherwise input 0 or FALSE or OFF output. So, it is also called
Inverter.
Algebraic Expression: R=A’
Graphical Symbols
A R=A’
Input Output A B R=A.B
1 1 1 1 0 0
0 1 0
0 0 0
Input Output A B R=A+B
1 1 1
1 0 1 0 1 1
0 0 0
Input Output
A R=A’ 1 0
0 1
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1.3.4. NAND Gate
NAND Gate is an electronic circuit which is used to perform complement of
logical multiplication. It is denoted by (. and ‘). It generate 1 or TRUE or ON
output if at least any one of the input is 0 or FALSE or OFF otherwise 0 or FALSE
or OFF output.
Algebraic Expression: R=(A.B)’
Graphical Symbols
A
R=(A.B)’
B
1.3.5. NOR Gate
NOR Gate is an electronic circuit which is used to perform complement of
logical addition. It is denoted by (+ and ‘). It generate 1 or TRUE or ON output if
all the inputs are 0 or FALSE or OFF otherwise 0 or FALSE or OFF output.
Algebraic Expression: R=(A+B)’
Graphical Symbols
A
R=(A+B)’
B
1.3.6. X-OR or EX-OR Gate
X-OR Gate is an electronic circuit which is used to perform logical “either/or”
operation. It is denoted by ( ). It generates 1 or TRUE or ON output if the
number of TRUE inputs are odd, therwise 0 or FALSE or OFF output. It is also
known as even parity generator.
Algebraic Expression: R=A B
Graphical Symbols
A
R=(A B)
B
Input Output
A B R=(A.B)’ 1 1 0
1 0 1 0 1 1
0 0 1
Input Output
A B R=(A+B)’
1 1 0
1 0 0
0 1 0 0 0 1
Input Output
A B R=(A B)
1 1 0 1 0 1
0 1 1
0 0 0
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1.3.7. X-NOR OR EX-NOR Gate
X-OR Gate is an electronic circuit which is used to perform logical complement of
Exclusive-OR. It generates 1 or TRUE or ON output if the number of TRUE inputs
are even, otherwise 0 or FALSE or OFF output. It is also known as odd parity
generator.
Algebraic Expression: R=(A B)’
Graphical Symbols
A
R=(A B)
B
1.4. Universal Gate
A Universal Gate is a gate which can implement any Boolean function without using any
other type of gates. NAND and NOR gates are known as universal gates.
EG:
A =A
Input Output
A B R=(A B)’
1 1 1 1 0 0
0 1 0
0 0 1
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2. Number System
A Number System is a system for expressing numbers that is mathematical notation
used for counting or manipulating other countable things. Here
Base Number System
2 Binary Number System
8 Octal Number System
10 Decimal Number System 16 Hexadecimal Number System
2.1. Binary Number System
A Number System having base or radix 2 is called Binary Number System. It consists
of two bits ie. 0 and 1.It is also called Binary Digits. Eg: (11011)2.
2.2. Octal Number System
A Number System having base or radix 8 is called Octal Number System. It consists
of number 0, 1, 2, 3, 4, 5, 6, 7, and 8. Eg: (6105)8
2.3. Decimal Number System
A Number System having base or radix 10 is called Decimal Number System. It
consists of number 0, 1, 2, 3, 4, 5, 6, 7, 8, and 9. It is also known as Denary Number
System. Eg: (9105)10
2.4. Hexadecimal Number System
A Number System having base or radix 16 is called Decimal Number System. It
consists of number 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, and character A, B, C, D, E, and F where
A=10, B=11, C=12, D=13, E=14, and F=15. Eg: (92A5)16
2.5. Conversation of Number System
Table:
Number System
Decimal Hexadecimal Octal Binary
0 0 0 0000
1 1 1 0001
2 2 2 0010 3 3 3 0011
4 4 4 0100
5 5 5 0101 6 6 6 0110
7 7 7 0111
8 8 10 1000
9 9 11 1001
10 A 12 1010
11 B 13 1011
12 C 14 1100
13 D 15 1101
14 E 16 1110 15 F 17 1111
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2.6. Decimal to Other Number System conversion
2.6.1. Decimal to binary conversion
Eg: convert (58.515)10=(?)2
0
1
0
1
1
(58)10=(111010)2
For fractional decimal,
Fractioned Multiplier Answer Integer 0.515 2 1.030 1
0.030 2 0.06 0
0.06 2 0.12 0
0.12 2 0.24 0 0.24 2 0.48 0
0.48 2 0.96 0
0.96 2 1.92 1
0.92 2 1.84 1
0.84 2 1.68 1 (0.515)10=(0.100000111)2
∴(58.515)10=(111010.100000111)2
2.6.2. Decimal to Octal conversion
Convert (697.687)10=(?)8
1
7
2
(697.687)10=(1271)8
For Fraction,
Fractioned Multiplier Answer Integer
0.687 8 5.496 5
0.496 8 3.968 3
0.968 8 7.744 7
0.744 8 5.952 5 0.952 8 7.616 7
0.616 8 4.928 4 0.928 8 7.424 7
0.424 8 3.392 3 0.392 8 3.136 3
Hence the equivalent answer is
(697.687)10=(1271.537574733)8
2 58
2 29
2 14
2 7
2 3
1
8 697
8 87
8 10
1
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2.6.3. Decimal to Hexadecimal conversion
Convert (4989.612)10=(?)16
13=D
7
3
For Fraciton,
Fractioned Multiplier Answer Integer
0.612 16 9.792 9 0.792 16 12.672 12=C
0.672 16 10.752 10=A
0.752 16 12.032 12=C 0.032 16 0.512 0
0.512 16 8.192 8 0.192 16 3.072 3
0.072 16 1.152 1 0.152 16 2.431999 2
The equivalent answer is
(4989.612)10=(137D.9CAC08312)16
2.7. Other System to Decimal conversion
2.7.1. Binary to Decimal conversion
Convert (111011.1101)2=(?)10
Here, (111011.1101)2 =1x25+1x24+1x23+0x22+1x21+1x20+1x2-1+1x2-2+0x2-
3+1x2-4 =59.8125
∴(111011.1101)2=(59.8125)10
2.7.2. Octal to Decimal conversion
Convert (7635.46)8=(?)10
Here, (7635.46)8 =7x83+6 x82+3 x81+5 x80+4 x8-1+6 x8-2
=3997.59375
∴(7635.46)8=(3997.59375)10
2.7.3. Hexadecimal to Decimal conversion
Convert (7D9A.EA)16=(?)10
Here, (7D9A)16 =7x163+D x162+9 x161+A x160+E x16-1+A x16-2
=7x163+13 x162+9 x161+10 x160+14 x16-1+10 x16-2
=32154.9140625
∴(7D9A.EA)16=(32154.9140625)10
2.8. Binary to Octal and Hexadecimal conversion
A. Binary to Octal conversion
Convert (1011101)2 = (?)8
16 4989
16 311
16 19
1
FCH 1: Fundamental of Computer
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Method 1:
Here, 001 011 101
1 3 5
∴(1011101)2=(135)8
Method 2:
B. Binary to Hexadecimal conversion
Convert (1011101)2 = (?)16
Method 1:
Here, 0101 1101
5 13=D
∴(1011101)2=(5D)16
Method 2:
2.9. Octal and Hexadecimal to Binary conversion
A. Octal to Binary
Convert (3756)8=(?)2
Method 1:
Here, 3= 011
7= 111
5= 101
6= 110
∴(3756)8=(11111101110)2
Method 2:
B. Hexadecimal to Binary
Convert (BC0)16=(?)2
Method 1: Here, B= 1011
C= 1100
0= 0000
∴(BC0)16=(101111000000)2
Binary Decimal Octal
Binary Decimal Hexadecimal
Octal Decimal Binary
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Method 2:
2.10. Octal to Hexadecimal and vice versa
A. Octal to Hexadecimal
Method 1:
Method 2:
B. Hexadecimal to Octal
Method 1:
Method 2:
2.11. Decimal Calculation
Complements are used in digital computers for simplifying the subtraction
operation and for logical manipulation. Using complements, all the arithmetic
operations can be performed in the form of addition.
2.11.1. 9’s Complement:
A 9’s Complement of a given decimal number is obtained by subtracting each
digit from 9.
For example:
9’s complement of 9 is 0 (9-9=0) and
678 is 321 (999-678=321).
2.11.2. 10’s Complement:
A 10’s Complement of a given decimal number is obtained by subtracting each
digit from 9 and finally adding one.
For example:
10’s complement of 9 is 1 ( 9’s complement of 9 +1 =0 +1 =1) and
678 is 322 (9’s complement of 678 +1=999-678+1= 322).
Hexadecimal Decimal Binary
Octal Binary Hexadecimal
Octal Decimal Hexadecimal
Hexadecimal Binary Octal
Hexadecimal Decimal Octal
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2.12. Binary Calculation
2.12.1. Binary Addition
Calculate sum of two binary numbers 101 and 110
101
+110
1011
2.12.2. Binary Subtraction
Substract 101 from 1011
1011
+ 101
0110
2.12.3. Binary Multiplication
0x0=0
0x1=0
1x0=0
1x1=1
2.12.4. Binary Division
Divide 110101 by 101
101) 110101 ( 1010
101
11
00
110
101
11
00
11
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3. Programming Language
The language like Nepali, English, Hindi,etc. used by human beings is called natural
language whereas the communication language between user ( human being) and
computer is called Programming Language. The language which is used to develop
program in computer is called Programming Language. Since a computer is electronic
device, it can only understand binary digit ie. 0 and 1.
3.1. Low Level Language
The low level language is a machine-oriented langunge so it is closer to what
machine can understand. It is difficult to write program using low level language.
Classified into two types
3.1.1. Machine Level Language (MLL)
Machine level language is first programming language used to make program in
computer. It is the language of CPU as it consists of series of 0’s and 1’s which
represents ‘off’ and ‘on’ state of electricity in computer circuit. Still modern
digital computer system uses Machine Level Language for processing and
storing data in 0 and 1 format. But, It is not used as programming language. The
MLL is also called generic language of digital computer.
Advantage of MLL
a. Program execution is faster than any other language as it is directly
understood and executed by the computer.
b. It does not require any translating program like compiler, interpreter or
translator because program itself is in binary form.
Disadvantage of MLL
a. It is very difficult and boring to make program in MLL since everything
should be in 0 and 1.
b. Program development is time consuming and almost impossible to
develop large program.
c. It is machine dependent language. So. The program written for one
processor cannot be used in others. Eg: the program for Intel processor
cannot run in AMD processor.
Programming Language
Low Level Language High Level Language Fourth Generation
Language
Machine Level Language
Assembly Level Language
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3.1.2. Assembly Level Language (ALL)
ALL came in existence to overcome the difficulties of Machine Language. In ALL,
instead of writing the instruction in the series of 0’s and 1’s, we can use
mnemonics like ADD, SUB, DIV, JMP, MOD, etc. along with the decimal number
in order to perform the different types of tasks and calculation.
Processing Architecture
Advantage of ALL
a. It is easier to write, debug and understand than MLL due to use of
mnemonics.
b. Program execution is faster than High Level Language.
c. It is efficient in program execution. Hence, ALL is still used in developing
firmware, device driver and operating system kernel.
Disadvantage of ALL
a. It is machine dependent language. The program made for one processor
does not work for other processors.
b. Program development and debugging is more difficult and time
consuming than in High Level Language.
c. It is very hard ot remember the mnemonics since they are in
abbreviated from and large in number.
3.2. High Level Language (HLL)
HLL is written in code of English language like structure and mathematical notation.
HLL instruction is not directly understood by the processor for execution. It need
conversion and the conversion is done by translating software like compiler and
interpreter. The Program written by the programmer in any HLL is called source
program. The codes that are converted into machine compatible or intermediate
code by compiler or interpreter is called Object Program. EG: Pascal, C, FORTRAN,
etc.
Advantage of HLL
a. It is easier to write, debug and understand HLL than other language due to
the similar structure of English language and mathematical notation.
Processor Source
Program
Object
Program
Assembler
Source Program
Compiler
Interpreter
Object Program Processor
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b. Program development is faster and require less effort than other languages.
c. Since it is machine independent programing language, program made up for
one processor can be used in otgher processor also.
d. Programmer does not need to remember larger number of mnemonics and
other unusual codes as in Low level language.
e. The programmer does not require the knowledge of internal structure of
computer architecture for writing the source programs in HLL.
f. Due to the similarity of English sentence, the source code itself provides
some form of technical documentation.
Disadvantage of HLL
a. Computer does not understand HLL directly, so the program needs
conversion before execution.
b. Program execution time is longer than in Low level language.
c. Every HLL must have its own translator because it cannot directly
generate executable code.
3.3. Fourth Generation Language (4GL)
Fourth Generation Language was developed after HLL, so it is one step ahead from
HLL. It is a result oriented programming language and it contains database query
language. 4GL program is also needed to be translated either by compiler or
interpreter into machine understandable code before they are executed as it is not
directly understood by the computer. Eg: SQL ( Structured Query Language).
3.4. Compiler
Compiler is software that converts source program written in HLL or 4GL into
machine level language at once. The compiler reads the complete program at first
and if it is bug free then it converts the source program in object program at once.
For every different processor or computer type, there must be a separate compiler.
It converts the source program into object program faster than interpreter does.
The process of running the compiler is called compiling. The object program consists
of binary file format and directly executed by the processor.
Source Program
Compiler
Interpreter
Object Program Processor
Processor Source
Program
Object
Program
Compiler
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3.5. Interpreter
Interpreter is also software that translates source program code written in HLL or
4GL into machine language line by line. Although the task of interpreter and
compiler is same, the working method of interpreter is different from compiler.
Unlike compiler, the interpreter reads each line of source program and if it is bug
free, then it convert program code into machine language. Since the interpreter
needs to evaluate the program line by line, it takes more time than compiler to
convert into machine language. The interpreter finds the error after translation of
every line of code.
3.6. Assembler
Assembler is translating software which converts, the source program written in
Assembly Level Language into object program which the computer can understand
for execution. It also read each line of Assembly Language code and if it is bug free,
then it translates the line into object program.
3.7. Difference between Compiler and Interpreter
Compiler Interpreter
1. It translates a complete high level language program into machine language at once.
1. It translates high level language program into machine language instructions line by line.
2. It finds the syntax errors during
compiling the whole programs.
2. It finds the syntax errors during
translating a line of the program.
3. The compiling process is faster than interpreter.
3. The interpreting process is slower than compiler.
4. It creates the object code after compiling.
4. It does not create object code at once.
5. Eg: C, C++, vb, etc. 5. Eg: BASIC, LISP, etc.
Processor Source
Program
Object
Program
Interpreter
Processor Source
Program
Object
Program
Assembler
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4. Software
Software is the computer programs, producers and documentation that performs
different tasks on computer system.
4.1. System Software
System Software is computer software designed to operate the computer hardware
and to provide a platform for running application software. System Software is a
collection of Operating Systems; device drivers, servers, windowing systems and
utilities. System software helps and application programmer in viewing away from
hardware, memory and other internal complexities of computer.
4.1.1. Operating System
Operating Systems performs basic tasks, such as It is the first program loaded
into memory when the computer is turned on and in a sense, bring life to the
computer hardware. Without it, you cannot communicate with your computer.
When you give the computer a command, the operating system relays the
instructions to microprocessor. When you are working in an application
software program such as Microsoft Word, Microsoft Excel, etc commands that
you give the application are sent through OS to CPU. Some of OS are Windows
95/98, Mac OS, Windows 7, DOS, Ubuntu, etc.
Function of OS are:-
Recognizing input from the keyboard
Sending output to display screen
Keeping track of files and directories on the disk
Controlling peripheral devices such as disk drives and printers
Provide security and backup
Provide interface between hardware and software
Management of memory
Scheduling processes
Software
System Software Application Software
Operating Software
Utility Software
Language Processor
Package Software
Tailor Software
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4.1.2. Utility Software
Utility programs help manage, maintain and control computer resources. These
programs are available to help you with the day-to-day chores associated with
personal computing and to keep out system running at peak performance.
Some examples of utility programs include:
Virus Scanning Software are designed to protect computer from computer
virus.
Backup Software is software that assists you in backing up your files and even
the entire computer hard drive. It is important to back up your files regularly.
Scan disk is a utility provided with Windows computers. It scans disks to see if
there are any potential problems on the disk such as bad sector areas.
Disk Defragmenter software assists you in keeps reorganizing disk drives.
After files are saved, deleted and resaved again, the disk can become
fragmented. It gathers those free spots and put them together to enable to
save data in most efficient manner.
4.1.3. Language Processor
Language Processor/ Translator is special types of computer system software
that can use to translate the program written in one language to another
language.
Types of language Processor/Translator
Compiler
Interpreter
Assembler
4.2. Application Software
Application Software enables the users to accomplish certain specific tasks. It
utilizes the capacities of a computer directly to dedicated task.
4.2.1. Package Software
Package Software is mainly designed by software companies to generalize
tasks. Hence it is also called general purpose software.
Common types of Package Software are:
Word Processing Software: This software enables the users to create and edit
documents. Eg: MS-Word, WordPad, Notepad, etc.
Database Software: Database Software allows the users to store and retrieve
data from databases. Eg: Oracle, MS Access, etc.
Spreadsheet Software: Spreadsheet software allows users to perform
calculations. They simulate paper worksheets by displaying multiple cells that
make up grid. Eg: MS-Excel, Lotus 1-2-3, etc.
Multimedia Software: They allow the user to crate and play audio and video
media. Players, Converter, burners, etc are some form of it. Eg: Window Media
Player, Window Movie Maker, etc.
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Presentation Software: The software that is used to display information int the
form of a slide show is known as presentation software. Eg: MS- Powerpoint.
4.2.2. Tailored Software
The software which are developed in high level language such as java, c, etc for
specific task is called Tailored Software. Eg: Banking Software, Billing software,
Ticketing Software, etc.
4.3. Computer Virus
Computer Virus is a kind of program that destroys the functioning power of
computer smoothly. There are 2 types of Virus according to functioning property:
Compiled Virus: which are executed by the operating system.
Interpreted Virus: which are executed by an application.
4.4. Antivirus
Antivirus software is a type of utility used for scanning and removing virus from your
computer. While many types of antivirus (or "anti-virus") programs exist, their
primary purpose is to protect computers from viruses and remove any viruses that
are found. Examples of common antivirus programs include Norton Antivirus,
Kaspersky Anti-Virus, NOD32 Antivirus, etc.
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5. Operating System
Operating System is the System Software which is designed to control the hardware of a
specific data-processing system in order to allow users and application programs to
make use of it. Eg: Linux, Mac OS, Microsoft Windows, etc.
5.1. Types of Operating System
Operating system is Categorized into 3 major group.
A. Based on processing method
a) Batch Processing
Batch Processing OS allowed to run only one program at a time. Batch processing
OS works on a series of programs which are held in queue. The jobs with similar
requirements were batched together and run as a group is called batch
processing. EG: an operator receives jobs in the series like FORTRAN, COBOL,
FORTRAN, FORTRAN and COBOL programs to run. If operator execute these
program on the same order. The operator has to run FORTRAN terminates it and
start COBOL again reloads FORTRAN and so on. If the operator runs 3 FORTRAN
and 2 COBOL programs as batch, this will save operator time.
b) Multitasking/ Multiprogramming
A running state of a program is called a task. Any operating System which
supports two or more active task or running programs simultaneously is called
multitasking operating system. It is also called Multiprogramming OS. EG: if any
operating system can run more than one program like word, spreadsheet, etc at
one monitor is called Multitasking OS.
c) Time sharing operating system
Time sharing OS is a kind of Multiprogramming OS which operates in an
interactive mode with quick response time. It allows the many users to
simultaneously share the computer resources. Eg: As the CPU switches rapidly
from one user to another user, each user feels that he/she has using his/her own
computer, which is actually one computer and its resources are shared among
many user by the help of OS.
d) Real Time Operating System (RTOS)
The primary objective of RTOS is to provide quick response time. RTOS is another
form of OS which monitors various input variables and process in short time or
within certain deadlines and performs its function.EG: Application used in flight
control, missile guidance, etc.
e) Multiprocessing operating system
Any Operating System which is capable of handling more than one processor and
its resources efficiently is called multiprocessing OS. It manages all available
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resources and schedules its function to program execution and interaction with
users.
B. Based on User Interface
a) CUI or CLI
CUI= Character User Interface
CLI= Command Line Interface
If the primary method of communication with the computer system is command
or text based system then this type of OS is called CUI or CLI. Eg: DOS, UNIX,etc.
b) GUI ( Graphical User Interface)
A visual computing environment that represents programs, files and options with
graphical images such as icons, menus and dialog boxes on the screen is called
GUI. Eg: Mac OS, MS Windows, etc.
C. Based on the mode of user
a) Single user OS
The OS which allows exactly one user at a time to operate Computer System at a
time is called Single user OS. Eg: MS-DOS, Windows 7, Windows XP, etc.
b) Multiuser OS
An Operating System that allows multiple users to user single computer
resources simultaneously on a single network server is called Multiuser OS. Eg:
UNIX, LINUX, etc.
5.2. DOS ( Disk Operating System )
DOS is a single user, and single task operating system. DOS was used in two versions
Microsoft version called MS-DOS and IBM version called PC-DOS. It has text based
user interface Ie. User has to use and type commands by using keyboard to get
computer response.
5.3. Windows
Window is an operating system which is an interface or bridge between computer
hardware and software, the hardware is really hard to understand, by using the
software we made soften the things and forgot about the hardness of hardware so
window is and user friendly interface between computer and user. It is a rectangular
area showing an application, document, contents of a folder or a dialog box when
you start computer. The Windows developed by Microsoft are listed below:
1) Windows 1.0, 2.0, 2.1x
2) Windows 3.0 and 3.1x
3) Windows 9x (95,98,ME)
4) Windows NT
5) Windows XP, Vista,7,
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6) Windows 8
5.4. Linux
Linux is a Unix-like operating System(OS) created by Linus Torvalds. He developed Linux
because he wasn't happy with the currently available options in Unix and felt he could
improve it. So he did what anybody else would do, and created his own operating
system.
When Linus finished building a working version of Linux, he freely distributed the OS,
which helped it gain popularity. Today, Linux is used by millions of people around the
world. Many computer hobbyists (a.k.a. nerds) like the operating system because it is
highly customizable. Programmers can even modify the source code and create their
own unique version of the Linux operating system. Web hosting companies often Install Linux on their Web servers because Linux-based
servers are cheaper to set up and maintain than Windows-based servers. Since the Linux
OS is freely distributed, there are no licensing fees. This means Linux servers can host
hundreds or even thousands of websites at no additional cost. Windows servers, on the
other hand, often require user licenses for each website hosted on the server.
Some of the linux OS are:
1) Red Hat Enterprise
2) CentOS
3) Ubuntu/Kubuntu
4) Debian
5) openSUSE
5.5. Mac OS
This is the operating system that runs on Macintosh computers. The company
dubbed it "Mac OS X," correctly pronounced "Mac OS 10." Unlike earlier versions of
the Mac OS, Mac OS X is based on the same kernel as Unix and has many advanced
administrative features and utilities. Though the operating system is much more
advanced than earlier versions of the Mac OS, it still has the same ease-of-use that
people have come to expect from Apple software.
The Windows developed by Microsoft are listed below:
1) Mac OS 8
2) Mac OS 9
3) Mac OS X (10)
5.6. Function of Operating System
Most of the Operating System can do following functions:
a) Process Management
Currently executing program or program segment inside CPU is called the
process. Process Management main concern is the execution of user programs
and system activities. This activities is called process. The process have 5 stage:
new, ready, running, waiting, end.
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New state: is the staring of any new program or application which want
microprocessor time.
Ready state: is the state lined for microprocessor time.
Running State: indicate job is being executing in the microprocessor.
Waiting State: pausing of the process execution on microprocessor.
End State: indicates the process has no longer exists on the microprocessor for
execution.
b) Memory Management
The OS mange all the memory devices like primary memory ( RAM and ROM).
Related to Memory Management, OS does following function:
i. Keep track which memory segment is using by whom.
ii. Manages for blank memory space available.
iii. Allocate and de-allocate memory space as needed.
iv. Decides location for storage of new program.
c) Storage Management
The OS also manage the secondary storage device like Hard disk. Related to
secondary device, OS is responsible for:
i. Free space, file and folders management.
ii. Reading and writing of data from disk and to the disk.
iii. Storage allocation and de-allocation
iv. Management of disk scheduling, formatting, cleanup and fragmentation.
d) Input/output Management
The OS plays a vital role in the management of input device like keyboard,
mouse, etc and output devices like monitor, printer, etc. Related to I/O
Management, OS is responsible for
i. To activate general device driver software.
ii. To run driver software for specific hardware when required.
iii. To manage buffer catching system for temporarily hold data and
information.
e) File Management
Files and Folder management is one of the most visible service of operating
system. Related to File and Folder Management, OS responsible for:
i. Creation and deletion of File and folder
ii. Support for manipulation of files and folder
iii. Backup files on non-volatile storage device.
iv. Mapping of files into disk storage.
v. Manages all system files and folders and protect it from unnecessary
deletion and modification
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f) Protection and Security
Protection is the process of securing the data and information from
unauthorized users. Related to Protection and security, OS responsible for:
i. Protection and security of files and directories.
ii. Hiding system files and directories from unwanted modification or deletion
iii. Preventing theft, corruption and loss of data
iv. Ensuring user authentication by promoting username and password
g) Network Management
A collection of autonomous computer system is called computer network.
Autonomous means each computer has its own local resources. Related to
network management, OS responsible for:
i. Sharing of resource even hardware or software.
ii. Sharing of data, information, files, etc.
iii. To generate communication medium
iv. To create single computer to server various workstations
v. To increase computational speed.
vi. To generate data availability and reliability.
h) Command Interpretation
The command is an input signal for the computer, on the basis of this command
computer produces its output. Related to command interpretation, OS
responsible for:
i. To translate the user command in computer readable form.
ii. Management of interface between hardware and peripheral devices like
printer, etc.
i) Virtual Memory Management
The OS manages the workable space by combining secondary storage device
and primary memory is called Virtual Memory. Related to Virtual Memory
Management, OS is responsible for:
i. Creating virtual memory by using two common methods paging and
segmentation techniques
ii. Maximum utilization of the primary and secondary memory
iii. For efficient execution of program on computer system even though it has
less amount of primary memory.
j) Backup and Recovery
Backup is the process of storing data and information on the drive. Recovery is
the process generating information from the stored devices. Backup and
Recovery ensures from the loosing data and provide facilities to come back
previous recovery point.
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