2. INDEX
Computer Overview
1. Introduction
2. Computers are Everywhere
3. What is a Computer?
4. Functioning of a Computer
5. Evolution of Information Technology
6. Evolution of Storage and Display Technologies
7. Types of Computers
Software Concepts
1. Introduction
2. Types of Software
3. System Software
4. Application Software
5. Open Source Concepts
6. Operating System’s Functions
7. Processor Management
8. Storage Management
9. Information Management
10. Some Commonly used Operating Systems
Data Representation
1. Introduction
2. Digital Number Systems
3. Number Conversions
4. Binary Representation of Integers
5. Binary Representation of Real Numbers
6. Representing Characters in Memory
7. ISCII
8. Unicode
Microprocessor Basics and Memory Concepts
1. Introduction
2. Microprocessor Basics
3. The Memory Devices
4. Ports
General OOP Concepts
1. Introduction
2. Evolution of Software
3. Programming Paradigms
4. Basic Concepts of OOP
5. Advantages and Disadvantages of OOP
3. INTRODUCTION
Computers have made great inroads in our everyday life and thinking. They are put to use for all sorts of
applications ranging from complex calculations or frontline research, engineering simulations down to
teaching, printing books and recreational games.
The areas of applications of computers are confined only by limitations on human creativity and
imagination. Any task can now be easily performed on a computer.
Therefore, it is essential for everyone in the society to know about a computer, it’s strengths, it’s
weaknesses and its internal structure.
4. WHAT IS A COMPUTER?
Computers can access and process data millions of times faster than humans can. A computer can store data and information in its
memory, process them and produce the desired results.
Computers can do a lot of tasks such as playing games, railway reservations, weather forecasting, error detection etc.
A computer is used essentially as a data processor. The term data and information are commonly used but they are very different from
each other. Let us understand the difference between them:
1. DATA - Data in computer terminology means raw facts and figures. For example, ‘Rahul’, ‘23’ etc.
2. INFORMATION – It means what we get after processing data i.e. information means meaningful data. For example,
‘Rahul, whose roll number is 23’.
What goes in the computer is Data and what comes out of the computer is Information. This process of turning data into information is
called the Information Processing Cycle.
5. INPUT UNIT, CENTRAL PROCESSING UNIT AND
OUTPUT UNIT
The input unit is formed by the input devices attached to the computer. The input unit is responsible for taking input and
converting it into computer understandable form (the binary code). Examples of input devices are: keyboard, mouse, joystick,
scanner etc.
The CPU is the control center of the computer. It guides, directs and govern its performance. It is the brain of the computer.
The CPU has two components: Control Unit (CU) and Arithmetic Logic Unit (ALU).
1. Control Unit – The CU guides and controls the interpretation, flow and manipulation of all data and information.
2. Arithmetic Logic Unit – The ALU performs all the four arithmetical (+, -, *, /) and some logical (<,>, =, <=,>=, <>)
operations.
The output unit is formed by the output devices attached to the computer. The output unit converts electrical signals coming
from CPU into characters, graphical or audio-visual form which can be understood by humans. For example, speakers, printers,
headphones etc.
6. THE MEMORY
The memory of a computer is more like a predefined working place, where it temporarily keeps
information and data to facilitate its performance. When the task is performed, it clears the memory and
memory space is then available for the next task to be performed.
A bit means a binary digit either 0 or 1.
A bit is an elementary unit of the memory. Eight bits together form a byte.
The memory of a computer can be thought of as ‘cell’. Each of these
cells is
further divided into smaller parts called bits.
7. HARDWARE AND SOFTWARE
Hardware represents the physical and tangible components of the computer i.e. the components that can be seen or
touched. Input devices, output devices, CPU, hard disk etc. are all examples of hardware.
Software represents the set of programs that govern the operation of a computer system and make the hardware run.
They are of three types, namely:
1. Operating System
2. Language Processors
3. Application Softwares
8. OPERATING SYSTEM
Hardware is nothing but finely designed machinery. Operating system makes the hardware work to produce results for
a task. The primary goal of an operating system is thus to make the computer system convenient to use and secondary
goal is to use computer hardware in an efficient manner.
The operating system performs the following functions:
1. Provides the instructions to prepare User Interface,
2. Loads necessary programs,
3. Coordinates how programs work with the CPU and
other hardware components, and
4. Manages the way information is stored on and retrieved
from disks.
There are various types of OS – single user OS, multiuser OS,
batch processing OS, multiprocessing OS etc.
9. LANGUAGE PROCESSORS
A language processor is a software program designed or used to perform tasks, such as processing program code to
machine code. Language processors are found in languages such as Fortran and COBOL.
The language processors are given below:
1. ASSEMBLER – This language processor converts assembly language into machine language.
2. INTERPRETER – This language processor coverts HLL program into machine language by converting and
executing it line by line.
3. COMPILER – This language processor also coverts HLL program into machine language but it
converts the whole program in one go and reports all the errors with line numbers.
10. APPLICATION SOFTWARES
An application program (app or application for short) is a computer program designed to perform a group of
coordinated functions, tasks, or activities for the benefit of the user. Examples of an application include a word
processor, a spreadsheet, an accounting application, a web browser, a media player, an aeronautical flight simulator, a
console game or a photo editor.
1. Custom software (also known as bespoke software or tailor-
made software) is software that is specially developed for some
specific organization or other user. These are made according to a
user’s requirements.
2. A general-purpose application, is the sort of software that you
use at home and school. Examples include word processors,
spreadsheets, databases, desktop publishing packages, graphics
packages etc.
11. STRENGTHS AND WEAKNESSES OF A
COMPUTER
There are some big advantages and disadvantages of a computer. These are as follows:
ADVANTAGES
• Speed – Computers are much faster as compared to humans and can perform a task in minutes or seconds which
might take days to perform manually.
• High Storage Capacity – Computers can store large amount of data in a very small space. A Hard Disk can store data
from 100GB to 10TB which is huge.
• Accuracy – Computers can perform all the calculations and comparisons accurately provided the hardware does not
malfunction.
• Reliability – Computers are immune to tiredness and boredom or fatigue. It makes them more reliable from humans.
• Versatility – Computers can perform repetitive jobs efficiently.
DISADVANTAGES
• Lack of decision making power – Computers cannot decide on their own. But scientists are trying to solve this issue.
• IQ zero – Computers are dumb machines with zero IQ. They need to be told everything.
13. THE GENERATIONS OF COMPUTERS
1. First Generation (1940-1956) – Vacuum Tubes
The first-generation computers were huge, slow, expensive, and often unreliable. They
generated a lot of heat and required very large space. It used vacuum tubes for circuitry.
Punched cards and paper tape were used for storage.
Examples: ENIAC, EDVAC, EDSAC
2. Second Generation (1956-1963) – Transistors
The second-generation computers were smaller in size, more reliable and faster, and
generated less heat.
They were mainly used for scientific purposes. These used transistors to transfer electronic
signals.
Examples: IBM 1400 and 7000 Series
3. Third Generation (1964-1971) – Integrated Circuits
The third-generation computers were smaller and less expensive, more affordable and
reliable. Microchip was used for the first time.
Examples: ICL-1900 series, IBM-370/168
14. THE GENERATIONS OF COMPUTERS
4. Fourth Generation (1971-Present) – Microprocessors
The fourth-generation computers were smaller, better, reliable and affordable.
This was the first time when computers began to be used in homes and offices.
Examples: Pentium, Power PC, AMD
5. Fifth Generation (Present and Beyond) – Artificial Intelligence
The fifth-generation computers will be using parallel-processing and
superconductors for better performance and results. It is currently in
development.
Examples: Many Robots and robotic devices
15. EVOLUTION OF DISPLAY TECHNOLOGIES
Cathode Ray Tube(CRT) –
Developed in 1897 and
was used in early
computers and
televisions.
Liquid Crystal
Display(LCD) – Suggested
in 1963 for display screen,
but were first used in
calculators and watches.
Plasma Monitors –
Released in 1964, they
found space because of
long life and bright
colors.
Touchscreen Monitors –
Although invented in
1965, but was first used in
2007 in Apple iPhone
16. EVOLUTION OF OPERATING SYSTEM
1. Command User Interface
A Command User Interface also known as character user
interface (CUI), is a means of interacting with a computer
program where the user (or client) issues commands to the
program in the form of successive lines of text (command
lines). A program which handles the interface is called a
command language interpreter or shell.
2. Graphical User Interface
The graphical user interface (GUI), is a type of user interface
that allows users to interact with electronic devices through
graphical icons and visual indicators such as secondary
notation, instead of text-based user interfaces, typed
command labels or text navigation.
17. TYPES OF COMPUTERS
Purpose Wise
1. Special-Purpose computers – Designed to perform a specific task.
2. General Purpose computers - A computer which can work on different types of programs and perform
many tasks.
Principle of Operation Wise
1. Analog Computer – These computers work with continuous physical quantities such as voltage, current
etc. They take input in the forms of volts, ampere, Celsius etc.
2. Digital Computers – This computer works with discontinuous data converted into binary form and all
operations are carried out on a very fast rate.
3. Hybrid Computers – They utilize the best qualities of both digital and analog computers.
18. SYSTEM SOFTWARE
System software is a type of computer program that is designed to run a computer's
hardware and application programs. It includes the following concepts:
1. Operating System – Interface between user and hardware
2. Utility Software – Ensures smooth working of a computer
3. Language Processor – Translates source code into machine code
4. Device Drivers – Contains set of instructions for the OS for operating a device.
19. BOOTING UP
Loading operating system files into main memory is called booting up or
bootstrapping. The process is as follows:
1. Diagnostic tests are taken out to check for all necessary equipment
2. A chip called RAM-BIOS is executed and read for OS files.
3. If OS files are found, the MBR is read for active partitions and loads secondary
boot records.
4. The secondary boot record now loads and runs the Bootloader program.
20. TYPES OF OS
Single User OS
• This OS supports
only one user at a
time.
• Windows, MacOS
Multiprogram OS
• This supports more
than one user at a
time.
• Unix, Linux
Time Sharing OS
• Each user is given a
fair share of CPU
time.
• BSD UNIX, GEnie
Real Time OS
• The jobs have fixed deadlines
and a job has to be
completed in that deadline.
• RT Linux
Multiprocessing OS
• It is capable of handling more
than one processors as the
jobs have to be executes on
more than one processors.
• Windows NT
Distributed OS
• This type of OS is designed to
share its work load over
multiple servers.
• DCE, X-Open
Interactive OS
• OS providing GUI
interface for
interaction with user.
• Android, iOS
21. UTILITY SOFTWARE
Utility Softwares are those helpful programs that ensures the smooth functioning of
the computer. These are meant to assist your computer. Some of them are:
1. Antivirus Software – Ensures virus-free work environment.
2. File Management Tools – Helps to browse, search, arrange your data.
3. Compression Tools – Facilitates compression of files.
4. Disk Management Tools – Used to manage data on disk to get optimum
performance.
5. Device Drivers – Contains sets of instructions for the OS on how to operate a
certain hardware device.
22. APPLICATION SOFTWARE
This type of software pertains to one specific application. These are programs written
by programmers to perform specific tasks. Some of them are:
1. Word Processing Software – Used for processing of textual matter and creation of
organized documents.
2. Electronic Spreadsheets – A program that accepts data values in tabular form and
allows user to analyze/calculate data.
3. Database Management Systems(DBMS) – Helps to organize collections of data
stored in your computer and provide various tools.
4. Graphic, Multimedia and Presentation Applications – Used for creating or editing
images or videos and to create attractive presentations.
23. OPEN SOURCE CONCEPTS
This term is used to refer those categories of software whose licenses do not impose
much conditions. Some of them are:
1. Free Software – Freely accessible, usable, customizable, improved, or distributed
2. Open Source Software – Freely usable, customizable, improved, or distributed but
not always free of cost
3. Proprietary Software – Neither open nor freely available, usable, customizable,
improved, or distributed
4. Freeware - Freely accessible, usable, distributed but can’t be customized
5. Shareware - Freely accessible, usable but for a limited period of time.
24. PROCESSOR MANAGEMENT
Processor Management means managing the processes or processors i.e. CPU.
Multiprogramming is way of function in which CPU shares active programs with
multiple users at a time.
It’s benefits are:
1. Increased CPU utilization
2. Higher Total job throughput
Throughput is an important measure of system performance.
𝑇ℎ𝑟𝑜𝑢𝑔ℎ𝑝𝑢𝑡 = 𝑁𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑗𝑜𝑏𝑠 𝑐𝑜𝑚𝑝𝑙𝑒𝑡𝑒𝑑 / 𝑇𝑜𝑡𝑎𝑙 𝑡𝑖𝑚𝑒 𝑡𝑎𝑘𝑒𝑛 𝑡𝑜 𝑐𝑜𝑚𝑝𝑙𝑒𝑡𝑒 𝑡ℎ𝑒 𝑗𝑜𝑏𝑠
25. JOB SCHEDULING
Job scheduling not only assigns priority to jobs but also admits new jobs for processing at
appropriate times. They are of two types:
1. Non-Preemptive Scheduling –
• First Come First Served(FCFS) Scheduling – The process which request CPU first, is
executed first.
• Shortest Job Next(SJN) – Whenever a new job is admitted, the shortest of the arrived is
selected and given the CPU time.
• Deadline Scheduling – The job with the earliest deadline is selected for scheduling.
2. Preemptive Scheduling –
• Round Robin – Gives all programs equal opportunity to make progress.
• Response Ratio – Response Ratio = Elapsed time / Execution time received
The job with the highest response ratio is preferred over others.
26. STORAGE MANAGEMENT
In the working of a modern computer system, memory plays a vital role. The CPU
reads from and writes to specific memory addresses. Various approaches to memory
management are:
1. Contiguous Storage Allocation
2. Non Contiguous Storage Allocation
3. Virtual Storage using Paging
4. Virtual Storage using Segmentation
27. INFORMATION MANAGEMENT
A computer system stores information, processes information, provides information
etc. Thus, managing this information is also an important task performed by the OS.
OS includes a component called ‘Information Management Component’ which are as
follows:
1. Physical IOCS – Responsible for device management and ensuring device
independence.
2. Logical IOCS – Responsible for efficient organization and access of data on IO
devices.
3. File System – Responsible for protection and controlled sharing of files.
28. COMMONLY USED OPERATING SYSTEMS
• Linux – It is a UNIX-based OS which is a famous example of free and open source software because it is
free of cost and its source code is also available.
• Windows - Microsoft Windows, is a metafamily of graphical operating systems developed, marketed, and
sold by Microsoft. Microsoft introduced an operating environment named Windows on November 20,
1985, as a graphical operating system in response to the growing interest in graphical user interfaces
(GUIs). Microsoft Windows came to dominate the world's personal computer (PC) market, overtaking Mac
OS, which had been introduced in 1984.
• BOSS - Bharat Operating System Solutions (BOSS Linux) is a GNU/Linux distribution developed by C-DAC,
Chennai in order to benefit the usage of Free/Open Source Software in India. It has enhanced Desktop
Environment integrated with Indian language support and other software.
• Solaris - Solaris is a Unix operating system originally developed by Sun Microsystems. Solaris has a
reputation for being well-suited to symmetric multiprocessing, supporting a large number of CPUs.
• Mobile OS
Android - Android is a mobile operating system developed by Google, based on the Linux kernel and
designed primarily for touchscreen mobile devices such as smartphones and tablets.
iOS - iOS (formerly iPhone OS) is a mobile operating system created and developed by Apple Inc.
exclusively for its hardware.
29. DIGITAL NUMBER SYSTEM
A number system is a set of symbols used to represent values derived from a common
base or radix. As far as computers are concerned, number systems can be classified
into two major categories:
1. Decimal number system
2. Binary number system
3. Octal number system
4. Hexadecimal number system
30. DECIMAL NUMBER SYSTEM
Decimal number system has ten symbols: 0, 1, 2, 3, 4, 5, 6, 7, 8, and 9, called digits. It is known as Base 10
system.
Conversion from Decimal to Binary
Use repeated division to convert decimal to binary by dividing the decimal number by 2.
1792 = 11100000000
Conversion from Decimal to Octal
Use repeated division to convert decimal to octal by dividing the decimal number by 8.
1792 = 3400
Conversion from Decimal to Hexadecimal
Use repeated division to convert decimal to hexadecimal by dividing the decimal number by 16.
1792 = 700
31. BINARY NUMBER SYSTEM
Binary number system has two symbols: 0 and 1, called bits. it is known as Base 2 system.
Conversion from Binary to Hexadecimal
Starting from the right-most bit (least-significant bit), replace each group of 4 bits by the equivalent hex digit (pad the
left-most bits with zero if necessary), for examples,
1001001010B = 0010 0100 1010B = 24AH
Conversion from Binary to Octal
To convert from binary to octal is to group binary digits into sets of three, starting with the least significant (rightmost)
digits.
11100101 = 011 100 101 = 345
Conversion from Binary to Decimal
The method involves addition and multiplication.
• Start the decimal result at 0.
• Remove the most significant binary digit (leftmost) and add it to the result.
• If all binary digits have been removed, you’re done. Stop.
• Otherwise, multiply the result by 2.
• Go to step 2.
11100000000 = 1792
32. OCTAL NUMBER SYSTEM
There are 8 unique digits available in octal number system. These are 0, 1, 2, 3, 4, 5, 6, 7. thus, any number formed is the combination of
these digits. It is known as Base 8 system.
Conversion from Octal to Binary
Converting from octal to binary is as easy as converting from binary to octal. Simply look up each octal digit to obtain the equivalent
group of three binary digits.
345 = 011 100 101= 011100101
Conversion from Octal to Decimal
Converting octal to decimal can be done with repeated division.
• Start the decimal result at 0.
• Remove the most significant octal digit (leftmost) and add it to the result.
• If all octal digits have been removed, you’re done. Stop.
• Otherwise, multiply the result by 8.
• Go to step 2.
345 = 229
Conversion from Octal to Hexadecimal
When converting from octal to hexadecimal, it is often easier to first convert the octal number into binary and then from binary into
hexadecimal. For example, to convert 345 octal into hex:
345 = 011 100 101= 011100101
Drop any leading zeros or pad with leading zeros to get groups of four binary digits (bits):
Binary 011100101 = 1110 0101
Then, look up the groups in a table to convert to hexadecimal digits.
Binary = 1110 0101
Hexadecimal = E 5 = E5 hex
33. HEXADECIMAL NUMBER SYSTEM
Hexadecimal number system uses 16 symbols: 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, A, B, C, D, E, and F, called hex digits. It is known as Base 16 system.
Conversion from Hexadecimal to Binary
Replace each hex digit by the 4 equivalent bits, for examples,
A3C5H = 1010 0011 1100 0101B 102AH = 0001 0000 0010 1010B
Conversion from Hexadecimal to Octal
When converting from hexadecimal to octal, it is often easier to first convert the hexadecimal number into binary and then from binary into octal. For
example, to convert A2DE hex into octal:
Hexadecimal = A 2 D E
Binary = 1010 0010 1101 1110 = 1010001011011110
Add leading zeros or remove leading zeros to group into sets of three binary digits.
Binary: 1010001011011110 = 001 010 001 011 011 110
Binary = 001 010 001 011 011 110
Octal = 1 2 1 3 3 6 = 121336 octal
Conversion from Hexadecimal to Decimal
Converting hexadecimal to decimal can be performed in the conventional mathematical way, by showing each digit place as an increasing power of 16.
A2DE hexadecimal:
= ((A) * 163) + (2 * 162) + ((D) * 161) + ((E) * 160)
= (10 * 163) + (2 * 162) + (13 * 161) + (14 * 160)
= (10 * 4096) + (2 * 256) + (13 * 16) + (14 * 1)
= 40960 + 512 + 208 + 14
= 41694 decimal
34. ONE'S COMPLEMENT
If all bits in a byte are inverted by changing each 1 to 0 and each 0 to 1, we have
formed the one’s complement of the number.
Original One's Complement
-------------------------------
10011001 --> 01100110
10000001 --> 01111110
11110000 --> 00001111
11111111 --> 00000000
00000000 --> 11111111
35. TWO’S COMPLEMENT
The two’s complement is a method for representing positive and negative integer values in binary. The useful part of
two’s complement is that it automatically includes the sign bit.
Rule: To form the two’s complement, add 1 to the one’s complement.
Step 1: Begin with the original binary value
10011001 Original byte
Step 2: Find the one's complement
01100110 One's complement
Step 3: Add 1 to the one's complement
01100110 One's complement
+ 1 Add 1
-------------
01100111 <--- Two's complement
36. ASCII
Binary Oct Dec Hex Character
011 0000 060 48 30 0
011 0001 061 49 31 1
011 0010 062 50 32 2
011 0011 063 51 33 3
011 0100 064 52 34 4
011 0101 065 53 35 5
011 0110 066 54 36 6
011 0111 067 55 37 7
011 1000 070 56 38 8
011 1001 071 57 39 9
100 0001 101 65 41 A
100 0010 102 66 42 B
100 0011 103 67 43 C
Binary Oct Dec Hex Character
100 0100 104 68 44 D
100 0101 105 69 45 E
100 0110 106 70 46 F
100 0111 107 71 47 G
100 1000 110 72 48 H
100 1001 111 73 49 I
100 1010 112 74 4A J
100 1011 113 75 4B K
100 1100 114 76 4C L
100 1101 115 77 4D M
100 1110 116 78 4E N
100 1111 117 79 4F O
101 0000 120 80 50 P
37. ASCII
Binary Oct Dec Hex Character
101 0001 121 81 51 Q
101 0010 122 82 52 R
101 0011 123 83 53 S
101 0100 124 84 54 T
101 0101 125 85 55 U
101 0110 126 86 56 V
101 0111 127 87 57 W
101 1000 130 88 58 X
101 1001 131 89 59 Y
101 1010 132 90 5A Z
010 1101 055 45 2D -
010 1110 056 46 2E .
010 1111 057 47 2F /
Binary Oct Dec Hex Character
010 0000 040 32 20 space
010 0001 041 33 21 !
010 0010 042 34 22 "
010 0011 043 35 23 #
010 0100 044 36 24 $
010 0101 045 37 25 %
010 0110 046 38 26 &
010 0111 047 39 27 '
010 1000 050 40 28 (
010 1001 051 41 29 )
010 1010 052 42 2A *
010 1011 053 43 2B +
010 1100 054 44 2C ,
38. MICROPROCESSOR BASICS
A microprocessor also called CPU is a multipurpose, programmable logic device that
reads binary instructions from a storage device called memory, accepts input and
processes data according to those instructions and provide results. Some of its basic
characteristics are:
1. Instruction Set - The possible operations a microprocessor can execute, is
determined through its instruction set.
2. Word Size – The number of bits processed in single instruction depend upon the
word size of a microprocessor. It determines the amount of information that can
be processed in one go.
3. Clock Speed – The speed at which the microprocessor executes instructions. The
faster the clock speed, the more instructions the microprocessor can execute per
second.
39. CENTRAL PROCESSING UNIT(CPU)
It is the central faculty responsible to carry out the designated tasks. It comprises of:
1. Control Unit – Supervises the operations.
2. Arithmetic and Logic Unit(ALU) – Carries out arithmetical and logical calculations.
40. MEMORY
This faculty is responsible for holding data and instructions. It comprises of:
1. Read Only Memory (ROM) – Holds pre-programmed instructions
2. Random Access Memory (RAM) – It is fast temporary memory that holds
programs, applications and data temporarily when an operation is taking place.
41. TYPES OF RAM
1. Dynamic RAM - DRAM is also a volatile memory that uses separate capacitors to store each bit.
Capacitors when not charged represent the value 0 of a bit and when charged represent the value 1.
Since the capacitors discharge with time, they need to be refreshed periodically to maintain the
values stored in them. Each memory cell in a DRAM consists of a capacitor and a transistor and these
cells are arranged in a square array. DRAMS are widely used for main memories in personal
computers and game stations since they are cheaper. DRAMs are manufactured as integrated circuits
(ICs) that come in plastic packages with metal pins that could be connected in to busses. Currently
there are DRAMs in the market that are manufactured as plug-in modules, which are easier to
handle.
2. Static RAM - SRAM is a type of RAM and it is a volatile memory, which looses its data when the
power is turned off. In a SRAM, each bit that stores data is made up of four or six transistors that
make up a flip-flop. There are additional transistors that are used to control read and write accesses
of storage cells. Even though typical SRAMs use six transistors to store each bit, there are SRAMs that
use eight, ten or more transistors to store a single bit. When the number of transistors is reduced, the
size of the memory cell decreases. Each SRAM cell can be in three different states called read, write
and standby. A cell is in the reading state when data has been requested and it is in writing state
when the data in the cell is modified. The cell is in the standby state when it is idling.
42. TYPES OF ROM
1. Programmable Read-Only Memory (PROM) – Can be programmed to record
information, but the recorded information can’t be changed once programmed.
2. Erasable Programmable Read-Only Memory (EPROM) - Can be programmed to
record information and can be erased to record new information.
3. Electrically Erasable Programmable Read-Only Memory (EEPROM) - Can be
programmed to record information and can be erased to record new information
only by using electrical signals
43. BUSES
It is a subsystem that concepts various computer components with CPU and transfers
data/instructions between them. They are of 3 types:
1. Address Bus – Carries address of a memory location or an input/output port
2. Data Bus – Carries the actual data TO and FRO memory location
3. Control Bus – Carries control signals such as clock signals.
44. INPUT-OUTPUT UNIT
This unit is responsible for getting data from input devices and sending output to
output devices. It comprises of:
1. Ports – Connections to IO devices.
2. Input Devices – Devices which provide input in various forms
3. Output Devices – Devices which get the result and produce it in human-
understandable form.
45. CLASSIFICATION OF MICROPROCESSORS
Microprocessors are classified:
1. By the width of data format (4-bit, 8-bit, 16-bit, 32-bit, 64-bit, or 128bit)
they process,
2. By their instruction set (CISC or RISC).
46. CACHE MEMORY
Pronounced as cash, the cache is a special high speed storage mechanism.
Memory cache is a portion of the high-speed static RAM (SRAM) and is effective
because most programs access the same data or instructions repeatedly. By keeping
as much of this information as possible in SRAM, the computer avoids accessing the
slower DRAM, making the computer perform faster and more efficiently. They are of
three types:
1. Level 1(L1) – Built inside the CPU package
2. Level 2(L2)
3. Level 3(L3)
} External to CPU and reside on
the motherboard
47. SECONDARY MEMORY DEVICES
Since primary memory has limited storage capacity and is not permanent, secondary storage devices are used
to store large amount of data permanently. They are as follows:
1. Floppy Disk – The floppy disk was one of the oldest type of portable storage devices but there use is now
discontinued.
2. Hard Disk – The hard disk stores information on one or more circular platters which are continuously
spinning. The tracks are divided into sections called sectors.
3. Compact Disk – They are a form of optical media which is relatively cheaper and have storage capacity of
up to 700Mb.
4. DVD – They look same as CD’s but can save up to 15 times the data stored on a CD.
5. Thumb Drives – They are a data storage device that includes flash memory with an integrated USB
interface. USB flash drives are typically removable and rewritable, and physically much smaller than an optical
disc. Most weigh less than 30 grams.
6. Blu-Ray Disk -Blu-ray or Blu-ray Disc (BD) is a digital optical disc data storage format. It was designed to
supersede the DVD format, in that it is capable of storing hours of video in high-definition (720p and 1080p)
and ultra high-definition resolution (2160p). The main application of Blu-ray is as a medium for video material
such as feature films and physical distribution of video games for the PlayStation 3, PlayStation 4, and Xbox
One. The name "Blu-ray" refers to the blue laser used to read the disc, which allows information to be stored
at a greater density than is possible with the longer-wavelength red laser used for DVDs.
48. PORTS
Ports are used to connect external devices to computer.
1. Serial Ports
2. Parallel Ports
3. Universal Serial Bus(USB) Ports
4. AGP Ports
5. InfraRed Ports
6. Bluetooth
7. PS-2 Port
8. Firewire
49. EVOLUTION OF PROGRAMMING LANGUAGES
A program serves the purpose of commanding the computer. The efficiency of a
program highly depends in which programming language it is made. These
programming languages are of two types:
1. Low-Level Programming Languages(machine and assembly language)
These are machine oriented and require extensive knowledge of computer circuitry.
Machine language uses binary codes(0 and 1) and assembly language uses symbolic
names for machine operations(READ, ADD etc.)
2. High-Level Programming Languages(HLL’s)
These programming languages offer English like keywords and use of variables and
constants. Thus, they are easy to use. The programs written in HLL’s are converted into
machine language using compilers.
First Generation Programming language
50. GENERATION OF PROGRAMMING LANGUAGES
• Also called machine language
• Consists of 0 and 1 only
• No compiler required
First Generation Programming
language
Second Generation Programming
language
Third Generation Programming
language
Fourth Generation Programming
language
•Based on solving using constraints given to the program, rather than using an algorithm written by a programmer.
•Prolog, OPS5 and Mercury are examples of fifth-generation languages.
Fifth Generation Programming
language
• Also called assembly language
• Used mnemonics instead of 0 and 1
• Assembler was used to translate code into machine language
• Designed to be easier to understand by humans
• Used basic English keywords
• Fortran, COBOL, ALGOL are some of them
• Designed to be closer to natural language
• SQL is one of the examples.
51. OBJECT-ORIENTED PROGRAMMING
Object-oriented programming (OOP) is a programming paradigm based on the concept of "objects",
which may contain data, in the form of fields, often known as attributes; and code, in the form of
procedures, often known as methods. A feature of objects is that an object's procedures can access and
often modify the data fields of the object with which they are associated (objects have a notion of "this"
or "self"). In OOP, computer programs are designed by making them out of objects that interact with one
another. There is significant diversity of OOP languages, but the most popular ones are class-based,
meaning that objects are instances of classes, which typically also determine their type.
Many of the most widely used programming languages (such
as C++, Object Pascal, Java, Python etc.) are multi-paradigm
programming languages that support object-oriented
programming to a greater or lesser degree, typically in
combination with imperative, procedural programming.
Significant object-oriented languages include Java, C++, C#,
Python, PHP, Ruby, Perl, Object Pascal, Objective-C, Dart, Swift,
Scala, Common Lisp, and Smalltalk.
52. BASIC CONCEPTS OF OOP
• Data Abstraction - Data abstraction is the reduction of a particular body of data to a simplified
representation of the whole. Abstraction, in general, is the process of taking away or removing
characteristics from something in order to reduce it to a set of essential characteristics.
• Encapsulation - Binding together the data and functions that manipulate the data, and that keeps both
safe from outside interference and misuse. Data encapsulation led to the important OOP concept of
data hiding. Data encapsulation is a mechanism of bundling the data, and the functions that use them
and data abstraction is a mechanism of exposing only the interfaces and hiding the implementation
details from the user.
• Modularity - Modularity refers to the extent to which a software/Web application may be divided into
smaller modules. Software modularity indicates that the number of application modules are capable of
serving a specified business domain. Modularity is successful because developers use prewritten code,
which saves resources. Overall, modularity provides greater software development manageability.
53. ADVANTAGES OF OOP
• Re-use of code – Linking of code to objects allows related objects to share code.
• Ease of Comprehension – The classes can be set up to closely represent the generic
application concepts and processes.
• Ease of fabrication and maintenance - Implementation details are hidden from other
modules and other modules has a clearly defined interface. It is easy to maintain
and modify existing code as new objects can be created with small differences to
existing ones.
• Easy redesign and extension – The same concepts facilitate easy redesign and
extension.
54. DISADVANTAGES OF OOP
• With OOP, classes tend be overly generalized.
• The relations among classes become artificial at times.
• The OOP program’s design is tricky.
• One needs to do proper planning and proper design for
OOP programming.
• To program with OOP, programmer needs proper skills
such as design skills, programming skills, thinking in
terms of objects etc.
