CBSE Informatics Practices Chapter-11 Basic Computer Organization

Chapter-1
Basic Computer
Organization
Done By: Faiz Muhammed
Grade: 11-D

A Computer Memory - is just like a human brain,is used to
store data and instructions. Computer memory is the
storage space in the computer, where data is to be
processed and instructions required for processing are
stored.A collection of cells, each with a unique physical
address.Most computers are byte-addressable.Cell at
address 11111110 contains 10101010.
E.g. for memory size-> if the computer has 64k words,
then this memory unit has 64 * 1024 = 65536 memory
locations. The address of these locations varies from 0 to
65535.

Memory Units – How much memory is required for a
file/data/progam etc. is measured by memory units. Following
are the memory units.

Memory is primarily of three types −
• Cache Memory
• Primary Memory/Main Memory
• Secondary Memory
Cache Memory - Cache memory is a very high speed semiconductor
memory which can speed up the CPU. It acts as a buffer between
the CPU and the main memory. It is used to hold those parts of data
and program which are most frequently used by the CPU.

Types of memory
The advantages of cache memory are as follows −
• Cache memory is faster than main memory.
• It consumes less access time as compared
to main memory.
• It stores the program that can be executed within a
short period of time.
• It stores data for temporary use.
The disadvantages of cache memory are as follows −
• Cache memory has limited capacity.
• It is very expensive.

Types of memory
Primary Memory (Main Memory) - Primary memory
holds only those data & instructions on which the
computer is currently working. It has a limited capacity
and data is lost when power is switched off. It is
generally made up of semiconductor device. These
memories are not as fast as registers. The data and
instruction required to be processed resides in the
main memory.
It is divided into two subcategories RAM and ROM.

Types of memory
Primary Memory (Main Memory) – Difference between RAM & ROM
BASIS FOR
COMPARISON
RAM ROM
Basic It is a read-write memory. It is read only memory.
Use store data to be
currently processed
required for booting
of computer
Volatility It is a volatile memory. It is a nonvolatile memory.
Stands for Random Access Memory. Read Only Memory.
Modification Data in RAM can be modified. Data in ROM can’t be
modified.
Capacity RAM sizes from 64 MB to 8GB. smaller than RAM.
Cost RAM is a costlier memory. cheaper than RAM.
Type Types of RAM are static RAM
and
dynamic RAM.
Types of ROM are PROM,
EPROM, EEPROM.

Types of memory
Primary Memory (Main Memory) – Types of RAM
BASIS FOR COMPARISON SRAM(STATIC RAM) DRAM(DYNAMIC RAM)
Speed Faster Slower
Size Small Large
Cost Expensive Cheap
Used in Cache memory Main memory
Density Less dense Highly dense
Construction Complex and uses
transistors and latches.
Simple and uses capacitors
and very few transistors.
Single block requires 6 transistors Only one transistor.
Charge leakage
property
Not present Present hence require power
refresh circuitry
Power consumption Low High

Types of memory
Primary Memory (Main Memory) – Types of ROM
MROM (Masked ROM)-The very first ROMs were hard-wired devices that contained a pre-
programmed set of data or instructions & are known as masked ROMs & are
inexpensive.
PROM (Programmable Read Only Memory)-PROM is read-only .The user buys a
blank PROM and enters the desired contents using a PROM program. Inside the
PROM chip, there are small fuses which are burnt open during programming. It
can be programmed only once and is not erasable.
EPROM (Erasable and Programmable Read Only Memory)-EPROM can be erased
by exposing it to ultra-violet light for a duration of up to 40 minutes. Usually, an
EPROM eraser achieves this function. During programming, an electrical charge
is trapped in an insulated gate region. The charge is retained for more than 10
years because the charge has no leakage path.
EEPROM (Electrically Erasable and Programmable Read Only Memory)-EEPROM
is programmed and erased electrically. It can be erased and reprogrammed
about ten thousand times. Both erasing and programming take about 4 to 10 ms
(millisecond). In EEPROM, any location can be selectively erased and
programmed.

Types of memory
Secondary Memory
This type of memory is also known as external memory or non-
volatile. These are slower than the main memory. These are used for
storing data/information permanently. CPU directly does not access
these memories, instead they are accessed via input-output
routines. For example Tape, disk, CD-ROM, DVD,pen drive etc.
Magnetic Tape
mass auxiliary storage device

Secondary Storage Devices
Hard disk
Fixed Head HDD / Movable head HDD
A hard disk is a set of stacked disks. Each disk has data recorded
electromagnetically in concentric circles, or tracks, on the disk
Hard Drive Types
1. Parallel Advanced Technology Attachment (PATA)
2. Serial ATA (SATA)
3. Small Computer System Interface (SCSI)
4. Solid State Drives (SSD)
Upto 12 TB sized HDD is available in the market

A Compact disc read-only memory (CD-ROM)- is a storage device that
can be read but not written to. The surface of a CD is made of a
polycarbonate layer with molded spiral tracks on the top. The data are
stored on the CD as a series of minute grooves which are known as
'pits' encoded on these spiral tracks. The areas between the 'pits' are
known as 'lands'. A CD burner is used to write (burn) the data on a
CD.A sensor reads data through light(laser) reflection.

DVD - Short for digital versatile disc or digital video disc, a
DVD or DVD-ROM is a disc capable of storing a significant
amount more data than a standard compact disc. DVD-ROM
drives that utilize these discs were first sold in 1997.Works
similar to cd but store data densely due to it’s faster speed.
DVDs have differing capacities.
• One of the most common DVDs is the single-sided, single-layer disc,
capable of holding 4.7 GB.
• The single-sided, double-layer disc is capable of holding between
8.5-8.7 GB.
• The double-sided, single-layer disc is capable of holding 9.4 GB.
• Although rare, the double-sided, double-layer disc is capable of
holding up to 17.08 GB.

Pen drive - is small storage device shaped like a pen with
built-in data storage that connects to a computer by a USB
port. It is based on old EEPROMS technology that allows
writing and erasure processes. When a pen drive is
connected to a USB port, it activates. Otherwise, it lies
dormant. Pen drives are used to store data. These flash
drives vary in storage capacity (64 MB to 128 GB) and are
removable and rewritable.

How data are deleted from
RAM – Data once stored in ram are not removed but are
replaced with new one or become inaccessible ,due to their
label(address) are detached from current program.
ROM – Deletion depends on rom type.(Read previous slide)
Magnetic tape - If the tape technology uses magnetic servo
tracks, they also will be destroyed and the tape will be
rendered useless. Note, however, that degaussing has to be
performed properly. The tapes need to be exposed to a
strong enough magnetic field for the correct amount of
time to completely destroy the data

How data are deleted from
Hard disk – When we format a hard drive or delete a
partition, we are only deleting the file system, making the
data invisible, or no longer actively indexed, but not gone.
CDRW/DVDRW – Through crystal rearrangement.
Pen drive/flash memory - The electrons in the cells of a
flash-memory chip can be returned to normal ("1") by the
application of an electric field, a higher-voltage charge.
Flash memory uses in-circuit wiring to apply the electric
field either to the entire chip or to predetermined sections
known as blocks. This erases the targeted area of the chip,
which can then be rewritten.

How data are recovered from
RAM:
We can't (in practice). RAM
needs to be constantly
refreshed to keep
"remembering", when the
computer is turned off the
charge leaks out after a
minute or so.
1.Freeze the chip, pop it into another computer, and run the
linux command dd to copy the raw data to disk.
After we have the raw data, copy it to a new partition using dd
again and run an undelete program on the partition. Undelete
should pull out any files that fall under a recognizable format
(ex pictures, etc...). The rest could be further processed but
not easily unless we know what you're looking for.

ROM – It depends on the type of ROM being used.
Magnetic tape - The procedure for recovering data from
magnetic tapes is very specialised and there are few
organisations capable of successfully achieving this(through
their specilised tool) and it depends on the condition of
tape also.
Hard disk – If hdd circuit is damaged then it will be replaced
and data will be recovered,this procedure is easy but if data
loss from disk track then it become harder to recover.if files
are removed due to command given mistakenly or
formatted mistakenly and no data then after over written
then these can be recovered from recua like software or we
can approach hdd repair & recovery company for the same
,they work in specialized environment ,specialist open hdd
and recover data bitwise that is too much harder process.

Pen drive – When the data are loss due to file system corruption or
accidently deleted and not over written,then data recovery software
can be used to recover the loss data. These software works at
hardware level and read each memory cell for recovery.

Security issue
RAM– RAM is used to store sensitive non-persistent
information in a lot of cases. Encryption keys would be a
common example.Sometimes it is possible to remove
RAM and place it into another device to dump the
contents.
ROM - Customs Roms are open-source and they have all
chance to steal data. But the developers stick to Their
ethics and refrain from such practices. Also security
teams watch what kind of additions are made to the
source codes.
Hard disk -Once our computer becomes infected with
malware, a cybercriminal can hijack our computer and
do almost anything they wish. A lot of malware these
days is programmed to seek out valuable or sensitive
data and send it back to the criminals.

Software - is an organized instructions/code
written by programmers using any of various
special computer languages for specific
purpose.
Purpose:
• Main purpose of software is to convert data into
information
• In business decision making
• Scientific investigation and engineering problem
solving
• Torun embedded system(t.v.,auto. washing
machine,dvd player etc.)
• Office automation
• Education

Types of software:
(1)Application software: It handles specialized/
common tasks a user wants to perform, such
as banking, hotel management, any data
processing, word processing etc.
(2)System software: controls the basic functions
of a computer & hides complexity of computer
system from user and application software.
E.g. Operating System, Compiler, Interpret etc.
(3)Utility software: Which helps to manage,
maintain and control computer resources. E.g.
are antivirus software, backup software and
disk tools.

System software:
OPERATING SYSTEM
An Operating System (OS) is a
system program that controls and
manages the computer
resources(resource manager) so
that application software can run
on it.
Example: Microsoft Windows,
Solaris, Linux, MAC OS,Ubuntu,
Apple’s i-Phone OS etc.

HOW OPERATING SYSTEM WORKS
In any computer or mobile device, the operating
system can be termed as the back bone when it
comes to software. This is because it has to be
there before other programs can be run.It works
as a middleman (interface) between machine and
user.
At the simplest level, an operating system does
two things:
•It manages the hardware resources of the
computer system. These resources include such
things as the processor, memory, disk space, etc.
•It provides a stable, consistent way for
applications to deal with the hardware without
having to know all the details of the hardware.

FUNCTIONS OF OPERATING SYSTEM
• Processor management
Loads, schedules and execute process/programs.
• Memory management
Allocates /De-allocation of memory for program execution.
• Device management
Communicate and controls various I/O devices.
• Storage management
Manages and controls the storage device to provide space to
program for execution & data save.
• Application interface
API/drivers provide a way for applications to make use of hardware
• User interface
structure for interaction between a user and the computer

TYPE OF OPERATING SYSTEM
* Single-User, Single Task Operating System:
These operating systems work on single task & single user at a time.E.g. DOS
* Single-User, Multi-Task Operating System:
These operating systems works on more than one task and process them
concurrently at a
time.E.g. windows 95 or later version of windows
* Multiuser Operating System:
In these OS, multiple users are allowed to access the same data or
information at a time via a network. E.g. Unix,Linux,Windows7,8,8.1,10.
* Multiprocessing Operating System:
Here, a single process runs on two or more processors. All the
processing and their management takes place in a parallel way,
hence this OS are also called as Parallel Processing. E.g. Linux, UNIX
and Windows 7.
* Embedded Operating System:
These are embedded in a device, which is located in ROM.E.g. OS of
microwaves,washing machine.
* Distributed Operating System:
In these OS, the computers work in co-operation with each other.

SYSTEM SOFTWARE/PROGRAMMING SOFTWARES
Language processor/Programming Language
As the computer understand machine language(0/1) where as Humans
understand High level/Human Lang.
Language Processors does the conversion task(high level to machine lang.)
These are of 3 types Language processors
1.Compilers-It convert high-level language code to machine code in one session. It
takes time because it have to translate high-level code to lower-level machine
language all at once and then save the executable object code to memory.
2.Interpreters-It translates code like a compiler but reads the code and
immediately executes that code, and therefore it is initially faster than a compiler.
3.Assemblers-It translates an assembly language program into machine language.
One-pass assemblers go through the source code once. Any symbol used before it
is defined will require "errata" at the end of the object telling the linker or the
loader to
"go back" and overwrite a placeholder which had been left where the as
yet undefined symbol was used.
Multi-pass assemblers create a table with all symbols and their values in the first
passes, then use the table in later passes to generate code.

S.N
O.
COMPILER INTERPRETER
1.
Scans the whole program in
one
go.
Translates program one
statement
at a time.
2.
the errors (if any) are shown
at the end together.
errors are shown line by line.
3.
Main advantageof compilers
is it’s execution time.
Due to interpreters being slow in
executing the object code, it is
preferred less.
4.
It converts the the
instructions into
systematic code.
It doesn’t convert the
instructions instead it directly
works on source language.
5 E.g. C, C++, C# etc. E.g. Python, Ruby, Perl, MATLAB
etc.
Difference between Compiler
and Interpreter:

Application software:
* General/Generic Purpose application
software These are ready to use software for
daily use purpose
e.g. word processor,spread
sheet,presention,DBMS etc.
* Specific Purpose application
software Softwares which are
designed for specific task
e.g. Payroll,Hotel Mgmt,Hospital Mgmt,Stock
Mgmt etc.

software
1. Word Processing Packages:
is a software which is used to process text. It
allows the user to type, view, edit, manipulate,
store and retrieve text material. With word
processors we can create well formatted
documents that may contain text and even
graphics. We can create letters, statements,
leaflets etc with a word-processing package.

software
2. Electronic Spreadsheets
is a software tool for manipulating data in
tabular form. A spreadsheet is a grid of
rows and columns. The intersections of
rows and columns are called cells.
In a spreadsheet cell, text, numbers or
formulas can be entered. Any formula
entered is automatically evaluated and
displayed by the program.

* General/Generic Purpose application software
3. Graphics and Multimedia Packages
Are software designed for creating and manipulating
images using a computer. Drawings, graphics and
pictures can be created and edited using graphic
Software.
Adobe photoshop, Paintshop pro, Ulead photo impact
etc. are popular image editing software for the windows
environment.

4. Database Management Systems
is a software used to manipulate large volumes of data
stored in well organized manner, called a database. A
database is a repository of related collections of data.
For example, a company database might contain
information about customers, suppliers, employees,
sales and inventory.The DBMS stores data in a way that
allows it to access those data at any time.

5. Desk Top Publishing (DTP) Packages :
DTP packages can be used for creating professional
quality documents and publications.DTP software
integrates the processes of design, typesetting and
pasteup into one task down. Through DTP We can
create an entire publication such as a textbook on a PC.
Examples of DTP Packages are Aldus PageMaker,
CorelDraw, Microsoft publisher etc. Some examples of
Indian, multilingual packages are, prakashak, Lipi, ISM,
Patrika etc.

* Specific Purpose application software
Softwares which are designed for specific task.E.g.
• Payroll- for employee salary purpose
• Medical store management
• Hospital management
• Hotel management
• Library management
• Airline/Railway/Bus reservation system
• Stock/Inventory management
• And there may be many more

Utility software:
that assist OS in carrying out certain specialized tasks are
called utility software.
 Antivirus - An anti-virus scans the system for any virus
and if detected, gets rid of it by deleting or isolating it.
 Compression tools - Compression tools are utilities
that assist operating systems in shortening files so that
they take less space.

 Disk Cleanup - Disk cleanup tools assist users in
freeing up disk space.
 Disk Defragmenter - Disk defragmenter is a disk
management utility that increases file access speeds
by rearranging fragmented files on contiguous
locations.
 Backup - Backup utility enables backing up of files,
folders, databases or complete disks.
 File management tools - Utility software providing
regular file management tasks like browse, search,
update, preview, etc. are called file management
tools.
 Restore – This utility restores the backup earlier taken.

CBSE Informatics Practices Chapter-11 Basic Computer Organization

CBSE Informatics Practices Chapter-11 Basic Computer Organization

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CBSE Informatics Practices Chapter-11 Basic Computer Organization