Path Wala
Computer
System Overview
1.1
1.1
Introduction
1.3 Mobile System Organization
1.2
Computer Components and
Basic Computer Organization
1.4 Types of Software
INTRODUCTION
Computers are the machines that have revolutionised the world around us. The way we used to
live around 25-30 years ago is very different from how we live today. A modern age student
cannot even imagine life, without email, Internet, print outs, playing music on computers or
smartphones, photos just a click away in the form of smartphones and so on. In short, in every
aspect of life around us, we see computers play a :i;ole directly or indirectly.
Computers deliver so much, diligently and efficiently, all thanks to the wonderful combination
of their hardware and software.
¢) Hardware.The physical electronic components of a computer are called hardware, e.g.,
keyboard, CPU, monitor, printer etc.
¢) _Software. These are the recorded instructions and programs that govern the working of a
computer. Recall that a program is a set of instructions to carry out a specific task or achieve a
special work goal.
In this chapter, we shall discuss computer's functioning in broad sense by discussing computer
system organization and how various types of software aid in computer's overall performance.
1.2
COMPUTER COMPONENTS AND BASIC COMPUTER ORGANIZATION
A computer system comprises of five basic components (see Fig. 1.1) :
(i) Input Unit. It is responsible for taking input for the computer. The input devices
attached to the computer system make the input unit.
(ii) Output Unit. It is responsible for taking input for the computer. The output devices
attached to the computer system make the output unit.
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Of-.i
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It · responsible for proces mg th d ta nd
_1s
(iii) Central Processing Unit (CPU).
.
.
It comprises of two parts .
mstruchons. .
. U 1·t (ALU). It is responsible for carrying out the anthm ti
nd
(a) Arithmetic a Logbic ~
ltiply divide) and making logic decisions (great r than,
instructions (add, su trac, mu
,
less than, equal to).
(b) Control Unit. It is respo_n~ible for
Secondary Storage
controlling and supervising the
processing.
(iv) Primary Memory. It is the internal volatile
memory where data and instructions are
stored during processing.
(v) Secondary Storage Unit. It refers
Central Processing Unit
Control Unit
Input
Device
to the external storage devices
which
provide
permanent
memory to the computer system.
Output
Device
Pnmary Memory
The components of a computer system
make the physical structure of a
computer whereas the logical structure
of a computer system is defined as
Computer Organisation.
l .2 l
Arithmetic/Logic Unit
Figure 1.1 Components of a computer system.
Computer Organisation
Computer organization refers to the logical structure of a computer describing how its
components are connected to one another ; how they affect one another's functioning, and
contribute to overall performance of the computer.
Computers, as you must be knowing, follow the 'IPO' principle i.e., Input ➔ Process ➔ Output
(a certain input is processed to generate specific output). So, the computer organization is
also like this - there are component(s) dedicated to obtain input in different forms,
component(s) dedicated to perform processing part and component(s) to produce output
in different forms.
Thus basic computer organization is as shown in Fig. 1.2. To see the interconnections and basic
working of computer (Computer Organization), scan this QR Code with SIPO app .
CPU
To see
Computer Organization
in action
.
[!]
~
j Registers
I
A computer runs on
electricity power.
I
Memory
•.
Scan
QR Code
BUS
Input
unit
Output
unit
Figure 1.2 Basic Computer Organization.
Storage
unit
l ct u t lk about the
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funct1onal compon nts of a computer, on by on
I put Unit
2
The_ mput unit i~ formed by the input devices attached to the computer. Exampl of p
de\ ices and media are : keyboard, mouse, magnetic ink character reader (MICR), optical m rk
reader (OMR), optical character reader (OCR), joystick etc.
The input unit is responsible for taking input and converting
.• into computer understandable form (the binary code). Since
a computer operates on electricity, it can understand only the
language of electricity i.e., either Oi\. or OFF or high voltage or
low voltage. That means a computer can understand two
stages ON/OFF or High/Low voltage or the binary language
that uses just two symbols: 1 for OJ\; and O for OFF.
An input unit takes the
converts ,t into b n ry form
that It can be understood by t
computer.
All the inputs consisted of data (on which the action was to be performed) as well as the instruction
(the action to be taken).
On th e same lines, the computer input also consists of data and instructions. For example, if
the given input to the computer is Add 2 and 3 then data consists of 2 an d 3 an d instruction is
Add . Similarly, if the given input is Print "Hello World" then data consists of "Hello World"
and instruction is Print.
The input unit is comprised of different input devices th at take the input in different forms and
pass them in digital form to CPU for processing.
Some common input devices are:
(i) Keyboard. Keyboard is a typewriter like device which is used to type in the letters,
digits and commands. For visually challenged people, Braille keyboards are also available
these d ays.
(ii) Mouse. Mouse is pointing device with either a roller on its base or some laser
mechanism. Mouse controls movement of pointer (also called mouse pointer) on screen.
(iii) Microphone (Mic). We can send sound input to computer through a special input
device called microphone or mic in short. A mic converts the sound received into
computer's format, which is called digitiz ed sound or digital audio.
A mic can work if your computer has a special hardware known as sound card.
1.2.3
Output Unit
The output unit is formed by the output devices attached to
the computer. The output coming from the CPU is in the form
of electronic binary signals which needs conversion in some
form which can be easily understood by human beings i.e.,
characters, graphical or audio visual form. This function of
conversion is performed by output units.
Output Unit converts the
output in binary form to
human readable form.
Some popular output devices are :
(i) Monitors. Monitor (or "screen") is the most common form of output from a computer.
It displays information in a similar way to that shown on a television screen. The
picture on a monitor is made up of thousands of tiny coloured dots called pixels.
For visually challenged people, Braille monitors are also available these days.
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COMPUTER SCIE"JCE WITH PYTHON
X
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Printers are the devices tha t deli ver
info rma tion by mea ns of printed
.
· k' I
·
cl1aracters on Pap er · Prin ters com e m van•ety o f form s, e.g., m
Jet, asel')et,
.
dotrnatri'x
.
printers etc. Unlike old style pri_nters,
whi ch prm ted on a pap er, these day s
3D printers
are also available whi ch can prm t/cr eate
3D mo del s.
(iii) Spe akers. Speakers receive the
sou nd in_ form of electric cur ren t from
the sou nd card
and then convert it to sou nd form at
aud ible to user.
(ii) Pnnters.
1.2.4 The CPU (Central Processing Unit
}
The CPU or the Cen tral Proces sing Uni
t is the mai n con trol cen tre and proces
sing unit. It is
also called brain of the com put er as it
gui des, directs, con trol s and gov ern s
the
per
formance of
a computer. The CPU has som e sub -co
mp one nts tha t hel p in carr yin g out the
processing of a
task. These are :
(i) Arithmetic Logic Uni t (ALU)
(ii) Con trol Uni t (CU )
(iii) Registers
(i) Arithmetic Logic Unit {ALU)
The ALU per form s all the four arit
hm etic (+, -,* ,/) and som e log ica l(<
,>,= ,<= ,>= ,!= )
operations. Wh en two num ber s are req
uire d to be add ed, thes e num ber s are
sen t from memory
to ALU whe re add itio n takes place and
the resu lt is put bac k in the mem ory .
In the sam e way,
other arithmetic ope rati ons are per form
ed (thr oug h AL U only).
For logical operations also, the num ber
s to be compared are sen t
from memory to ALU whe re the compari
son takes place and the
ALU performs arithmetic
result is retu rne d to the mem ory . The resu
(+, -, *,/) and logic
lt of a logical ope ration
is either TRUE or FALSE. These operatio
operati ons.
ns provide the capability
of decision-making to the computer.
{ii} Control Unit (CU)
The CU control s and gui des the inte
rpre tati on, flow and man ipu lati on
of all data and
information. The CU sen ds control sign
als unt il the req uire d ope rations are don
e pro perl y by
ALU and memory. Ano ther imp orta nt
fun ctio n of CU is the program execut
ion i.e., carrying
out all the inst ruc tion s stor ed in the pro
gra m. The CU gets pro gra m inst ruc tion
s from memory
and executes them one after the other.
After gett ing the inst ruc tion s from mem
ory in CU, the
inst ruction is decoded and inte rpre ted
i.e., whi ch ope rati on is to be per form ed.
Then the asked
ope rati on is carried out. After the wor
k of this inst ruc tion is com plet ed, con
trol uni t sends
signal to mem ory to sen d the next instruc
tion in seq uen ce to CU.
The control uni t eve n controls the flow
CU acts as a supervisor by
of dat a from inp ut
devices to mem ory and from mem ory
controlling and guiding
to out put devices.
(i ii} Registers
Registers or processor registers are sma
ll
units of data holding places. The CPU
uses
registers to temporarily hol d som
e
impo.~tant processing-information dur
ing
the time the processing is taking plac
e.
CPU may store some par t data or som
e
memory address or some instruction in
its
processor registers.
the operation taking place.
Modern days' smart machines (e.g.
, washing machines,
microwave oven etc.) also come with
embedded CPUs. In
fact, these embedded CPUs are more
than the CPU as
these also contain little ROM, RAM
and other required
circuitry containing some embedde
d instructions. These
embedded CPUs with accompa
nying memory and
embedded instructions are called mlcr
ocontrollers.
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COMPUTER SYSTEM OVERVIEW
5
1.2 5 The Memory [Main Memory/Pri·mory Memory]
The memory of a computer is more like a predefined working place, where it temporarily keeps
information and data to facilitate its performance. Each memory location has a unique memory
address. When the task is performed, it clears its memory and memory space is then available
for the next task to be performed. When the power is switched off, everything stored in the
memory gets erased and cannot be recalled.
The memory of a computer can be thought of as 'cells'. Each of these cells is further broken
down into smaller parts known as bits (see Fig. 1.3). A bit means a binary digit i.e., either Oor 1.
A number of bits·together are used to store data instructions by their combination.
r=
. . . . . . ···· ··· ········ ··- ········r··r
. .. . . ·· .
0
1
0
0
0
1
1
Bit
Cell 0
Cell 1
0
The memory of computer Is
often called main memory or
primary memory.
................. . .......... .
Figure 1..3 Memory cells.
A bit is an elementary unit of the memory. Eight bits together form a byte.
One byte is the smallest unit which can represent a data item or
a character. Other units of memory are KB, MB, GB, TB etc.
Every higher memory unit is equal to 2 10 of its lower unit.
Following Table 1.1 lists various memory units used.
~BYTE OR
NIBBLE '
A group of 8 bits is called a byte
and a group of 4 bits is called a
nibble.
T ab le 1.1 Units of Computer Memory Measurements
Unit
Short Name
Full Name
Unit
10
Short Name
Full Name
i.e., 1024 GB
1 TB
Terra Byte
2 10 i.e., 1024 TB
1 PB
Peta Byte
2 10 i.e., 1024 PB
1 EB
Exa Byte
Mega Byte
2 10 i.e., 1024 EB
1 ZB
Zetta Byte
Giga Byte
210 i.e., 1024 ZB
1 YB
Yotta Byte
1 Bit
Bit
Binary Digit
8 Bits
1 Byte
Byte
210 i.e., 1024 Bytes
1 KB
Kilo Byte
210 i.e., 1024 KB
1 MB
210 i.e., 1024 MB
1 GB
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Since computer's main memory (primary memory) is temporary, secondary memory space is
needed to store data and information permanently for later use. Some most common secondary
storage media are the hard disk, CD-RWs, pen drive etc. The secondary memory devices are
also known as storage devices.
l .2.5A
Parts of Main Memory/Primary Memory
In the random-access memory (RAM), the memory cells can be accessed for information
transfer from any desired random location. That is, the process of locating a word in memory is
the same and requires an equal amount of memory, thus the name "random access".
The main drawback of RAM memory is that it is a volatile memory. That is, when the power
goes off, the contents of RAM get erased.
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The RAM chips in a com pute r can be of two basi
c type s:
(i) Dynamic RAM (DRAM). These are_ mad e
up of tran sisto rs and capacitors. The amount
f t' e take n to prod uce data requ ired from mem
ory, from the star t of access until the
~va~:bility of data is called memory access time
. Tod ay's DRA M chip s hav e access times
ranging from below 20 to 70 nanoseconds.
(ii) Static RAM. These are mad e up of flipMEMCfaY ACCESS Tl ME
flops 1 and offer
faster access times (abo ut 10 nan osec ond s) than
The amo unt of time ta ken to
DRAMs.
produce data requ ired from
Static RAMs are thus used in spec ializ ed app
lica tion s
mem
ory, from the start of access
while dyn ami c RAMs are use d in the prim ary
stor age
until the availabilit y of dat a, is
sections of mos t com pute rs.
called Mem ory
Access Time .
Read Only Memory (ROM)
As the nam e implies, a read -onl y mem ory (RO
M) is a mem ory unit that perf orm s the read
operation only; it doe s not hav e a writ e capa
bility. This imp lies that the bina ry information
stor ed in a ROM is mad e perm ane nt duri ng the
hard war e pro duc tion of the unit and cannot be
altered by writ ing diff eren t wor ds into it (hen
ce non-volatile). Wh erea s a RAM is a generalpurp ose device who se con tent s can be alte red
duri ng the com puta tion al proc ess, a ROM is
restricted to read ing wor ds that are perm ane
ntly stor ed with in the unit . ROM s are used for
applications in whi ch it is kno wn that the info rma
tion nev er nee ds to be alte red, for example, a
mon itor prog ram con troll ing a machine. These,
how ever , are slow er than RAM.
There are vari ous type s of ROM whi ch are give
n belo w :
(i) PROM (programmab le ROM). Also call
ed OTP (One Time Programmab le). PROM is a
user -pro gram mab le mem ory in whi ch info rma
tion is bur nt usin g special equipment
called a ROM burner.
(ii) EPROM (erasabl e program mab le ROM
). In EPROM, one can prog ram the memory
chip (thr oug h various mec han isms e.g., UV
radi atio n) and eras e it man y times as
need ed. The UV-EPROM can take up to 20 min
utes for eras ing EPROM contents.
(iii) EEPROM (electrically erasable prog
rammab le RO M). In EEPROM, the EPROM
is
- erased electrically whi ch is faster. Also, with
EEPROM, selective bytes can be erased
unlike UV-EPROM which erases fully .
(iv) Fla~h EEPROM. It is like EEPROM but
is very fast com para tively (the eras ure of the
entire contents take s less than a seco nd) . Also
, it eras es fully and not selectively.
(v) Mask ROM. Mask ROM refers to a kind of
ROM in whi ch the con tent s are programmed
by the IC manufacturer. It is not a user -pro gram
mab le ROM.
1.2.6 Cache Memory
Pronounced as ~ash, the cache mem ory is a spec
ial high -spe ed
storag
e mec h~s m. It can be either a rese rved sect ion
of mai n
memory or an mde pen den t high -spe ed stor age
device or eve n
on CP:1 chip. Whe~e:7e~ som e data is requ ired
, the CPU first
look s m the cache, if it is ther e or not. If the data
is foun d in
cache, CPU does not access mem ory and hen
ce
becomes very fast.
the proc ess
1. A flip-flop ia a b
CAC HE MEM ORY
The Cache Mem ory is a high
speed mem ory available inside
CPU in orde r to speed up access
to data and instructions stored
in RAM mem ory.
Chapter 1 : COMPUTER SYSTEM OVERVIEW
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A memory cache, sometimes called a cache store or RAM cache, is a portion of memory made of
high-speed static RAM (SRAM) instead of the slower and cheaper dynamic RAM (DRAM) used
for main memory. Memory caching is effective because most programs access the same data or
instructions over and over. By keeping as much of this information as possible in SRAM, the
computer avoids accessing the slower DRAM.
When data is found in the cache, it is called a cache hit, and the effectiveness of a cache is judged
by its hit rate. 95% of the time the processor is working, it is accessing information from cache.
1.2.7 The Storage Unit
Computers need to store and retrieve data for processing.
Since primary memory has a limited storage capacity and is
not permanent, secondary storage devices are used to store
large amount of data permanently. There are various types of
secondary devices available these days.
To specify the storage capacity of storage devices, same units
of memory are used, which are used for measuring primary
memory. That is, we can represent the storage capacity of
storage devices in terms of kilo bytes (KBs), mega bytes (MBs),
gigabytes (GBs) and tera bytes (TBs) as we do for main memory.
ti•foN iui-tilt~
Wi•• 1tf$J · · ·
❖ Hard disks -_, Magnetic
Media
❖
CD ROMs
❖ DVDs
❖
Pen drive
J
Optical
Media
J
Flash
memory
Let us now talk about some most common storage devices.
1. Hard Disks
1.
(i) Storage of 1 KB means
following number of bytes :
the
(a) 1000 (b) 964 (c) 1024 (d) 1064
(ii) One Megabyte is equivalent to
(a) 210 bytes (b) 220 bytes
(c) 230 bytes (d) none of the above
2. What are the functional components of
a digital computer ?
3. What are the components of CPU ?
What is its role ? What is the function
of control unit of CPU ?
4. What role does the input unit play in a
computer ?
5. What is the function of ALU ?
6. What role does the output unit play in
a computer ?
7. What is the function of main memory ?
What are the measuring units of memory ?
8. What are different types of ROM ?
9. What is the role of cache memory ?
10. Which storage device is considered a
portable device ?
The hard disk memories store information on one or more
circular platters (or disks) which are continually spinning.
These rotating disks are coated with a magnetic material
and stacked with space between them. Information is
recorded on the surface of rotating disks by magnetic heads
as tiny magnetic spots.
The hard disks of today have storage capacity measured in
giga bytes upto tera bytes.
2. Compact Disks (CDs)
The compact disks or CDs are optical media. The CDs are
relatively cheap and have a storage capacity of upto 700
Mb. There are three main types of CDs:
(i) CD-ROM (Compact Disk-Read Only Memory).
This is used only to store information and cannot
be used to store data. It is mainly used for CD
distribution e.g., software, games, e-books etc.
(ii) CD-R (Compact Disk-Recordable). It is !li.ainly used
for CD-Rand can be written on only once and disk
can't be erased.
(iii) CD-RW (Compact Disk-Rewritable). CD-RW is an
erasable disk you can write on multiple times.
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3. DVDs
. th t 1 ks the same as a compact disc but is able to hold ab
DVD is an optical storage de:7ice ~ t oonsfer it to the computer about 20 times as fast out
15 times as much informatidon an r;ensity disk (SD), can hold upto 17 gigabytes of da:s a
CD ROM A DVD also calle a 5uper
. .
aor
·
'.
'd DVDs also come in three varieties.
four hours of movies on a si e.
. ..
.
. .
d 1 DVDs i e 1 once recorded 1mt1ally, you cannot write on it
(i) DVD-ROM. Th is 1s rea on y
··
,
•
•
(ii) DVD-R (DVD-Recordable). DVD-R similar to CD-Rs allow users to write on the disc
once but read it many times.
(iii) DVD-RW (DVD-Rewritable). Most writable DVD drives are DVD-RW You can erase
and read many times on them.
4. Flash Memory
A flash drive is a small, ultra-portable storage device with
a 'solid state' memory i.e., it has no
moving parts unlike magnetic storage devices, nor does it m~ke use of_ lasers - u~like ~ptical
drives. Instead, it works in a similar way to RAM. The key difference 1s that data 1s retamed in
Flash memory even when the power is switched off. They are now fairly inexpensive, costing from
~ 250/- upwards. Typical sizes range from 256 Mbytes up to 128 GB and beyond.
5. Blu Ray Disk
Blu-ray Disc (also known as Blu-ray or BO) is an optical disc storage media format. Its main uses
are high-definition video and data storage. The disc has the same dimensions as a standard
DVD or CD. While current optical disc technologies such as DVD, DVD± R, DVD± RW, and
DVD-RAM rely on a red laser to read and write data, the new format uses a blue-violet laser
instead, hence the name Blu-ray. The benefit of using a blue-violet laser (405 nm) is that it has a
shorter wavelength than a red laser (650 nm), which makes it possible to focus the laser spot with
even greater precision. This allows data to be packed more tightly and stored in less space, so it's
possible to fit more data on the disc even though it's the same size as a CD/DVD. Blu Ray disks of
today are capable of storing upto 128 GB of data.
l .2 .8 The System Bus
The system bus_ (or the bus) is an electronic pathway composed of connecting cables and that
connects the ma1or components of a computer system. Through system bus, data and instructions
are passed among the computer system components.
¢)
¢)
¢)
¢)
1.3
The data carrying part of system bus is called data bus.
The control instruction carrying part of system bus is called control bus.
The memory address carrying part of system bus is called Address bus.
Ad s~parate htype of bus called 1/0 Bus connects the Input Output and other external
ev1ces to t e system.
'
MOBILE SYSTEM ORGANIZATION
Modem mobile system are tiny com t
.
·
power compared to their b ·
P1:1 ers m your hand. Although they have less computing
igger versions they handl d 1·
ch as
making calls through radio signals, offer~ ca
~. _verse type of applications su
display audio/video/graphical cont t b hg _mer~ utilities, handling touch sensitive screen,
en ut avmg httle batte b d
Thus, the system organizatio f
b'
ry ase power etc.
.
n a mo 1le system has
1 ck
d iagram
of a mobile system is as show . p·
components to handle all these. Thebo
nm 1g. 1.4.
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Chapter 1 : COMPUTER SYSTEM OVE RVIEW
9
Olaplay Subsystem
Touch sensitive Interface
Keyboard
,-
Camera Unit
(Image Signal
Processor)
Display screen
----- - - - - - - - -CPU
RF Transceiver
I
SIM
Radio Signal
Management
COMMUNICATIONS
PROCESSOR
(Digital Signal
Processor)
APU (Application
Processing Unit)
Storage
GPU (Graphic
Processing Unit)
External
Storage
Power Management
Battery
pack
Battery
management
CODEC
DAC
Memory
Charger
Audio
Subsystem
Mic
Speaker
Figure 1.4 Mobile System Organization.
major
days
These
components of a mobile
syst em are integrated on
a single ch ip called
System on a Chip (SoC) .
The Soc chips consume
less power compared to
othe r alternatives .
Let us talk about these functional components of a mobile system one by one.
A mobile system's CPU handles diverse types of applications but has a little power compared to
computers as mobile systems run on battery power.
l . Mobile Processor (Mobile CPU)
This is the brain of a smartphone. The CPU receives commands, makes instant calculations,
plays audio/video, stores information and sends signals throughout the device.
The CPU of a mobile system has majorly two sub-processor 2 types : (i) Communications
Processing Unit (ii) Applications Processing Unit (APU)
(i) Communications Processing Unit. [Mobile System I/O Unit] This subsystem is
responsible for making and receiving phone calls on a mobile handset. It has a digital
signal processor that helps it work with RF Transceiver and the Audio subsystem.
is responsible for connecting SIM (which
provides a type of modem) to the base stations through radio signals. (3GILTE/4G
based cellular networks).
¢) Radio Signal Management Unit
(ii) Applications Processing Unit (APU). This subsystem is responsible for governing,
controlling all types of operations taking place on a mobile system by running various
types of mobile applications (apps).
2. I n fact , major subsystems are like processors in themselves
signal processor .
e.g., Radio Signal Management system can be termed as Radio
COVP
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.
"din display facilities, touch sensitive interface and
This subsystem is responsible for prov1
g
touch sensitive keyboards.
3
s
ni
.
Thi ubunit is designed
to d e1·iver a tightly bound image processing package. andI enable an
ss
.
d •deo experience. It has an integrated Image S1gna Processor
improved overall picture an v1
.
b ·1 · .
d th
.
l'k
· tan t image capture, high-resolution support, zmage sta z zzatzo11, an o er
ensures things
1 e ms
image enhancements.
4 f A-1....·I
<;,
--L--
Mom rm,
Like its other counterparts, a mobile system also needs memory to work. A mobile system's
memory is comprised of following two types of memories :
(i) RAM (Random Access Memory). It is the work memory of your mobile system. The
installed mobile apps, when run, are first loaded in the RAM and then executed. These apps
remain in the RAM after you are no longer using them and then they are shifted to background.
The more RAM you have on a smartphone, the better the performance and faster the phone will
generally be. RAM does not store information once the device is turned off.
(ii) ROM (Read Only memory). The ROM or Read Only Memory is a part of mobile system's
internal storage and it is not accessible for users to write on and is thus referred to as Read Only
Memory. The ROM is basically Flash memory or technically EEPROM (electrically erasable and
programmable read only memory).
This ROM part of a mobile system internal storage is where
operating system resides. It also has some preinstalled apps in
this memory sections which cannot be deleted on users' end
either. ~sis the reason why you don't get full internal memory
as advertised on the Box, because a part of it has been used to
house operating system and other pre-installed apps.
RAM memory is volatile, it loses
its contents when you switch off
the device .
5 . Storage
.. ,...,..,6-~
~
1.2
1. What are major functional components
of a mobile system ? ·
2. What is the role of Communication
processor of a mobile system ?
3. How does a mobile system manage and
draw power ?
4. What is the role of display management
unit of a mobile system ?
5. How does memory of mobile function ?
6. How does t he CPU of a mobile system
work?
The external storage of a mobile system is also called
ex~andable storage. It comes in the form of SD cards, or
micro SD cards etc. It is the storage which can be removed
e~sily by you and can be used for storing pictures, music,
videos and the likes. To an extent, even the cloud storage
can also be categorized as external storage.
6
· _Power Management Subsystem (Battery)
This subsystem is
'bl
b .1
responsi e for providing power to a
mo ~ e system. The mobile systems work on limited power
provided through
ch
has a batte m
an atta ed battery unit. This subsystem
charger ryd anagement system that works with a battery
an a battery unit
d
mobile syst
.
.
, an provides power to th e
em m required form.
Chapter 1 · COMPUTER SYSTEM O ✓ERYIEW
1.4
Path Wala
11
TYPES OF SOFTWARE
A computer sy 5t em consists of hardware and software for its proper functioning.
Ha rdware represents the physical and tangible components of the computer i.e., the components
that can be seen and touched. Input devices, output devices, CPU, hard disk, printer etc. are
examples of computer hard}vare.
Sofhoare represents the set of programs that govern the operation of a computer system and
make the hardware run. Software can be classified broadly into two categories.
1. System Software
2. Application Software
Follm, ing sections discuss system software and application software in details.
1.4.1 System Software
A computer is mere a machine that knows nothing of itself. Rather it requires instructions for
each and e\ erything it performs. These instructions are provided to it through software. The
sotn,·are that controls internal computer operations (viz. reading data from input devices,
transmitting processed information to the output devices, checking system components, converting
data, instructions to computer understandable form etc.) is known as system software.
The system software can further be classified into two categories :
1. Operating System
2. Language Processor.
Let us discuss each one of these individually.
SYSTEM~SOfTWARE
The
software
that
controls
internal computer operations is
called System Software.
1.4. l A Operating System
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. An operating system is
an important component of a computer system which controls all other components of the
computer system.
Major components of a computer system are :
1. The Hardware
2. The Operating System
3. The Application program routines (compiler, linkers,
database management systems, utility programs)
OPERATING' Sys'fEM
An Operating System is a
program which acts as an
interface between a user and
the hardware (i.e., all computer
resources).
4. The Humanware (users)
where hardware provides th<.· basic computing resources, the 11pplicatio11 program ro11ti11es define the
ways in which these resources arc used to solvt.• the computing problems of the users and the
Operating System controls and coordinates the use of the hardware among the various
application programs for the various users.
An operating system's major role is to execute a program. How an operating system executes a
program, is covered in chapter 4.
There are different types of operating systems available today to cater to varied type of
requirements. These are : Single user OS, M11/tiuser OS, Time sharing OS, Real time OS,
Multiprocessing OS, Distributed OS etc.
We are not discussing these operating systems types here as it is beyond the scope of the syllabus.
l .4.1 B Language Proce~sors
Path Wala
. 1t)rpe of a computer softv.,are that can translate the source cod
ocessor is a spec1a
.
f h
A language pr
ch '
ode Here you should know the meaning o t e terms source cod
into an object code or ma me c
.
e
or object code.
.
.
fers
to
the
program-code
written
by
a
programmer
m
a high level
e) A source co de re
C
programming language (HLL) such as in C, Jav~, ++ etc.
.
e) An object code refers to a code usually in machme language or bmary code, a language
that computer can understand easily and run on hardware.
So, you can safely say that language processors are software that conve_r t sourdc~ codes into object
codes. There are three types of language processors : assembler, compz 1er an mterpreter.
(i) Assembler. This language processor converts the program written in assembly language
into machine language.
(ii) Interpreter. An interpreter is a type of system software that translates and executes
instructions written in a computer program line-by-line, unit by unit etc.
(iii) Compiler. A Cqmpiler is another type of system software that translates and executes
instructions written in a computer program in one go.
The translated machine code runs fast (faster execution time) as now computer does not require
any type of conversion to run it i unlike source code which requires con version into
object/machine code before it can be executed.
Chapter 4 (section 4.3) discusses the working of compilers and interpreters in details.
1.4 .2 Applicati on Software
This type of software pertains to one specific application. For instance, a software that can
perform railway reservation functions cannot prepare result for a school.
These are the programs written by p rogrammers to enable computer to perform a specific task
such as_ pro~ess~g words, inventory control, handling calcu lations and figures, medical
accounting, financial accounting, result p reparation, railw ay reservation, billing etc.
Application software can further be subdivided into four categories :
~>APPLICATION SOFTWARE
l. Packages
2. Utilities
An Application Software is the
3. Customised Software
set of programs necessary to
4. Developer Tools
carry out operations
specified application.
1.4 .2A Packages
for
a
Only syste~ software does not suffice for efficient use of computers because t_h_e _s_y_st-em
so=are eXIsts m_ostly for the benefit of the computer. Other programs i e the application
~tt aret adre ralmeqmred to make the computer useful for people. Application. s~ftware has been
en o o
ost every task imagm·able fr
d
. .
, om wor processing to selecting a college to attend ·
As applications may be numerous (fr
th
ds
software for each one of them. Rathe:: ousan to millions of them), it is not feasible to design
individual users in the mann ·t .
general software are designed that may be used by
er
i
suits
their
needs and
·
software are known as packages.
requirements. Such general-app1·ica ti'0 n
om:
Some major and most common cate ories O f
(i) Word Process·
S f
g
general application software (packages) are:
mg o tware
("") 5
(iii) Database Man
zz preadsheets
agement Systems
(i ) D k
(v) Graphics, multimedia and
. v es top Publishing Software
,
presentation applications.
13
CO\I\PU
Path Wala
1.4 .28 Utilities
Utilities are those helpful program s that ensure the
s~ooth fu~~t~oning of the compute r. Utility programs or
simply Uhhhes are meant to assist your compute r. Some
utilities h~lp you backup data, some help remove
outdated files or recover data that has been accidentally
~rased. ~ome make it easier to find and arrange the
mforma hon you need. And some help you avoid virus
attacks or clean viruses, if any. In other words, the utility
program s perform house-k eeping functions.
application
Utilities are those
by
computer
programs that assist the
performing housekeeping functions
like backing up disk or scanning /
viruses
cleaning
Informatio n etc.
or
arrangingj
It is an establish ed truth that everythi ng comes with certain pros and cons. Software also are not
an exceptio n to it. Utilities bridge the gaps by helping to solve the problem s and maximiz e your
compute r's potentia l. Some importa nt utilities are being discusse d below.
1. Text Editor. This utility program is used for creating, editing text files.
2. Backup Utility. This utility program facilitates the backing -up of disk. Back-up means
duplicat ing the disk informa tion so that in case of any damage or data-loss, this backed
up data may be used.
3. Compre ssion Utility. This utility program facilitates compres sion of files. Large files can
be compres sed so that they take less storage area.
4. Disk Defragmentor. A file is fragmen ted when it becomes too large for your compute r
to store in a single location on a disk. When this happens , your compute r splits the file
up and stores it in pieces. You can use fragmen ted files, but it takes your compute r
longer to access them.
Disk Defragmentor utility program speeds up disk access by rearrang ing the files and
free space on your compute r, so that files are stored in contiguo us units and free space
is consolid ated in one contiguo us block.
s. Antivirus Software. This utility program ensures virus-free work environment. A computer
virus is a maliciou s compute r program that disrupts normal function ing of a compute r.
An antivirus software scans your disk for viruses and removes them, if any virus is
found. Moreove r, some antivirus software remains present in memory all the time so
that they can detect the viruses (as soon as they occur) and countera ttack them.
Application Software
Word processors
Spreadsheets
Graphic
design
software
Databases
System Software
Hardware
Operating
System
CPU, disks, mouse,
printer, etc.
Language
processors
Utilities
Device
drivers
Figure 1.5 Working hierarchy in a computer.
Presentation
software
Path Wala
COMPUTER SCIENCE WITH PYTHO
14
.
.
. to a business
,.,_!
reqmrements
cifically created software according
..tJUS
.
.
.
spe
IS
This type of software
. d veloped to meet the general reqmrements of a busmess. For instance
type of so ftware IS e uterize its' Accounts' department and gets a software that can scr\'c ,ita
.
o cOmpis business software. There are many readymade busmess
company wan ts tftware
softwares
nee d s. Suc h a So to a variety of business needs. Examples of these software are Inventory.
can cater
These
Management System (for managing inventory details of a company), Payroll system (for
handling payroll of a company's employees), Financial Accounting, Hotel Management and
Reservation System etc. Although there are standard business software available in market, yet
some companies prefer getting customized (tailor~made) software as per their sprcific
requirements. However, such softwares cannot be directly installed at any o ther user's
workplace as the requirements of the second user may differ from tlw first and tlw software
may not fit in the requirements of the new user.
1.4 .2C Business Software.
Software Libraries
l .4 .3
When programmers develop software and programs, lhcy h,wL~ a prl'w l'illl'l1 sl'l of
~ode/~nctions, classes, scr!pts etc. available to do a variety of tasks, which they l'.1 11 rnw dirl•clly
m the1~ code. These ?redefmed sets of codes are ca lled software liL>rtHit•s. /\ softw.ue librnry is 11
1
predefined_ and av~1lable to use, suitt;? of data and prngr:u. .... t4 codl' in llw for m of pn wrillt•11
code/funct1ons/scnpts/classcs etc. th al can be ust.·d in the devl'lopnw nl of 1ww soflwnn'
programs and applica ti ons.
The c:,oftware libra ri es combine codes/ fun ct ion s / scrip ts / clnssL'H dr. 0 11 tlw h.11-, is 1)1 tlwir
, (unc•t·1nrw 1·tt y, u progrnrnnwr lll'L'd 8 to ,1dd tli,11
.
.
.
In order to use lht• rcwri lt·en
domain.
common
~ibranec:, to itc:, cod_c. For instance, if yo u r sofl wnn• l'l'CJUi l'L'H1-,onw lw.ivy rn.1l lw 111 i1 t ic,1l w ork llu•11
yr>u r:d.;d n<Jt ~nlc the ~un cli onH/m d, , c> lc. for <'0111pl vx 11 w tli1·m.i tic.i l lu 1H·lio11H. 1-!.itill'I' wl111t
y <JtJ n.:td t<) do 1s lh,1t t·o 1n r lucl e/impor l ;111 nvu il ,ihlt•
SOrTWARE LIBRARIES
math babCc.l c.,<Jflware Ji brn ry in your prngrn in . Tlll'n
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' 1 ~ ~~i i,. librnry in
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t.11
COMPUTER SYSHM OVERVIEW
LET
~
Us
Path Wala
REVISE
re and software.
Computers , an deliver performance because of an efficient co111bi11at1011 of hardwa
e represent the reco rded
While hardware refers to physical electronic components of a computer, softwar
inscructionslsoftware that govern its operation.
interconnections and work
Computer organization refers to logical structure of a computer describing their
dependency.
Unit, Output Unit.
The {unctional components of a computer include : input unit, CPU, Memory, Storage
ng it to digital form.
<& The Input unit is responsible for obtaining input from user and converti
a set of instructions and produces output.
<& The CPU (Central Processing Unit) processes the received input as per
s.
<& The CPU has these sub-components : ALU, Control Unit and Register
tic operations and logic operations (e.g.,
<& The ALU (Arithmetic of Logic Unit) is responsible for carrying out arithme
comparing two values).
% The Control Unit controls or supervises the processing taking place.
memory address during the
Registers are small data holding areas within CPU that hold data, instructions and
processing.
processing.
% The main memory or memory holds the data and programs for the
% Main memory can either be ROM or RAM.
instructions.
~ ROM is read only memory that stores some prewritten
for manipulating data during processing.
'<& RAM is Random access memory that can be read and written and is used
as soon as power goes off.
'<& The primary memo,y (RAM) is volatile in nature as all contents are erased
recently accessed data.
<& The cache memory is a special high speed memory storing the most
% The storage unit stores the contents permanently.
y discs.
% Major storage devices are hard disks, CD, DVD, flash drive and Blue-Ra
output and processing.
<& A mobile system handles complex types of operations including input,
Management subsystem, Display subsystem,
% Major functional components of a mobile system are Radio Signal
power management subsystem, CPU, Memory and storage subsystems.
n of a computer system and make the hardware run.
'Q. Software represents the set of programs that govern the operatio
software.
'a: The software that controls internal computer operations is called system
the user and the hardware.
% An operating system is a program which acts as an interface between
OS, time-sharing OS, real-time OS,
'<'u TherP are different types of OSs available - single program OS, multiprogram
multiprocessing OS etc.
to machine language.
'<'u A language processor converts a program written in high level language
language code to machine code, (ii) compiler
% ThPre ar<' three language prcx·Pssors: (i) assembler which converts assembly
and (iii) interpreter which convert high level language code to machine code.
ns for a specified application.
% Application software is a set of programs necessary to carry out operatio
and (iii) customised software.
% There are three categories of application software : (i) packages (ii) utilities
of the utilities are : text editors, backup
~ Utility programs assist the computer in maintaining its performance. Some
utilities, compression utilities, disk defragmentors, and antivirus software.
ents.
<:t. Customised software is tailor made software according to user's requirem
available to programmers for use in the
'<& Software libraries are sets of prewritten code/functions/classes etc.
development of new code.
~
]
.
{._ ) bj e ct i v e TYPe Qu e s t '· o n s
Multiple Choice Questions
1. Which
Of
Path Wala
OTQs
.
?
h following components is the mam memory of computer .
t e
(b) DVD
(a) CD
(c) Internal hard drive
(d) RAM
2 Which component of a comPuter connects the processor to the other hardware ? .
· (a) System Bus
(b) CPU
(c) Memory
(d) Input Umt
3
Which of the following is referred to the brain of computer ?
(a) Processor
(b) RAM
·
(c) ROM
(d) Hard drive
4. What is the name of programs that control the computer system ?
(a) Hardware
(b) Keyboard
(c) Software
(d) Mouse
5. The physical components of a computer are called ?
(a) Software
(b) Hardware
(c) ALU
(d) CPU
6. Which of the following is the common measurement of unit or computer memory ?
(a) IQ
(b) Byte
(c) Terabyte
· (d) Gigabyte
7. What is the name of the component that used to both read and writes data ?
(a) ROM
(b) RAM
(c) Hard Drive
(d) Cache Memory
8. The CPU is also known as:
(a) The Brain
(c) The Central Processing Unit
(b) The Processor
(d) All of these
9. Which smaller unit of the CPU directs and coordinates all activities within it and determines the
sequence in which instructions are executed, sending instructions sequence to other smaller unit.
(a) CU
(b) ALU
(c) PROCESSOR
. (d) All of these.
JO. Which smaller unit of the CPU performs all arithmetic and logic functions in a computer?
(a) CU
(b) ALU
(c) PROCESSOR
(d) All of these.
11. Component of CPU which is responsible for comparing the contents of two pieces of data is
(a) ALU
(b) CU
(c) memory
(d) register
12. In a computer, CU stands for
(a) control unit
(b) cache unit
(c) calculating unit
(d) communication unit
13. Arithmetic and logic unit alo
·th
I
·
·
kn own as
ngwi contra umt of a computer' combined into a single unit,
15
(a) central processing unit
(c) I/0 unit
(b) memory unit
(d) operating unit
I.
Path Wala
J,apter 1 · COMPUTER
17
SYSTEM OVERVIEW
14. \Vnrd Processor and Desktop Publishing program are the examples of
(d) none of these
(c) cpu
(/J) software
(11) H,miwc1re
1, Opt' rc1tmg System is an example of
(11) Applic-.1tion Software
(c) Utilit) program
lo.
(b) System software
(d) none of these
\ dis!-. fragnwntor is an example of
Application Software
(t) Utilit) program
(t1)
(b) System software
(d) none of these
17. Flash memor> and Blu Ray disk are the examples of
(c) cpu
(lJ) software
(t!) Hardw,1re
(d) none of these
lS. Fl.1sh memor) is a type of ___ memory
(b) RAM
(11) Pnmar)
(d) all of these
(c) secondary
14. Which of the following memory types will store the data or information permanently?
(b) cache
(d) Hard disk
( •) RAM
(c)
Flash Memory
20. \ \ hich of the following memory types cannot store the data or information permanently ?
(b) cache
\'') RAM
(L, Flash Memory
(d) Hard disk
Fill in the Blanks
1. _ _
refers to the logical structure of a computer describing their interconnections and dependency.
2. RAM and ROM are the types of _ _ _ memory .
3. The _ __ is responsible for carrying out arithmetic and logic operations.
4. The _ _ _ of the CPU controls or supervises the processing taking places.
5 The small memory providing units inside the CPU are called the _ __
6. The _ __ memory is a special high speed memory storing the most recently accessed data.
7. The power unit of a mobile system is called _ __
8. The set of programs nccl'ssary to carry out operations/tasks pertaining to a specific application, are
called ______
9. Software that control s and manages inll'm,11 computer opL'rations is called ______
10. Utility progrnm s
Ml'
a typt• of ______ .
11. Antivirus software is a tnw of ______ .
12. Windows OS is a type of ______ .
True/False Questions
1. A computer system consists of both hardware and software.
2. Hardware is a set of instructions called programs that the computer uses to carry out tasks while
Softwar(' are all thl' parts of the computer you can see and touch, also known as peripherals.
3. Thl' two smallL'r units of the Processor are CU and ALU.
18
Path Wala
\1 m M mory hold d t
t: 1bl by the CPU
nd m tru t1
b n
pr
d
t
A mob ile y tern also cont ains a CPL: .
A mob ile syste m work s with elec tnaty .
7 A mobile system has its own Jittle pow er unit
8. A cache mem ory is a type of RAM.
9
f ;inguagc processors are a type of applicati
on software.
IC c ustum iscd softw are is a type of sy.-:,tem sofh-vare.
NOTE : Answers for OTQs are given at the end of the
book.
S"oh,e~ ProbleW1s
I.
Slate the basic units of t/ie computer. Name the s11bu11its that
make up the CPU, and give Ille funcJ,on of
of the units.
Solu tion. The basic units of a com pute r ar(!:
1. Inpu t unit
2. Cent ral Proc essin g Unit (C PU)
3. Outp ut Unit
4. Memory.
The CPU has two subu nits: the control unit (CU)
and the arithmetic logic unit (ALU ).
The control unit cont rols the entire oper ation bein
g ca rried out.
The ALU perfo rms the arith meti c and logical o pera
tions.
2.
3.
What is the ftmction of memory ? What are its meas uring
units ?
Solution . The mem ory temp orari ly hold s the data
and infor mati on duri ng proc essing.
The smal lest unit of mem ory is a byte (8 bits). A
byte can store one char acter in bina ry form . Other
meas uring units are kilobyte (KB) equa l to 1024 10
(2 ) byte s, Meg abyt e (MB) equa l to 1024
KB,
Giga byte (GB) equa l to 1024 MB and Tera byte (TB)
equa l to 1024 GB.
Give examples for each of system software and applicatio
n software. Explain the function of each type.
Solu tion. Exam ples of syste m softw are are :
(i) Oper ating syste m
(ii) Lang uage Proc esso r
(iii) App licat ion Softw are
Exam ples of Ope ratio n Syst em are: Single user OS,
multiuser OS, batch processing OS, multiprocessing
OS etc.
As the nam es suggest, single user OS supp orts singl
e user wher eas multiuser OS can supp ort m_ultipl;
users. The batch processing OS processes the batch
es (grou ps) of jobs (processes given to it) an
multiprocessing OS is capable of hand ling mult iple CPU
s at the same time.
The examples of language processors are : (i) Inter prete r
(ii) Com piler (iiL) Assembler
An interpreter conv erts and executes an HLL prog
ram into object prog ram line by line whert:'.as a
compiler converts an HLL prog ram into object prog ram
in one go and once the prog ram is error frCC
it can be executed later. An assembler conv erts an assem
bly lang uage prog ram into object program
Lxamples of application software are : (i) Cust omis ed Softw
are (ii} Gen('ral soft" are.
The cuE.tomised software perta ins to the requ irem ents
of a specific user for who m the sott\, are ha~
been developed. General software is deve lope d keep
ing in mind gc>neral spe1.. itications of J problel11•
MPUTER SYSTEM OVERVIEW
Path Wala
19
. , J111'111CJ1 I/ /111/ '11m1 d1•.,f 11u /,vc rtad' 111i:111ory ?
. write
,
\\11y zs. p1 i111ary 111c11rnrii
• lermccl ac; ,c1LSfmctrvc
. read from in the primc1ry memory, the rnntl'nl'l of the: m mory
o Iuhon. When a memory
S
. loc a fion is
\\'llt d remain the
.
are n< )t aIt ercc.I ·rI1crc fore, .i prirn<1ry
memory ii;; h.'rmcd a 'nm
.
destructive, read' same , they
.
memory smcc the re a d opera t.10n cIoes not cIestruct the cnnlcnlo of a memory word.
4
.
a wnte
When th,
1
contents of the memory word .irc ovcrwntttm.
the prC'v1ous
. Pace,
. operation takes
Th
· opcr,1tion destructs
· , memory as the wntc
•
'd
·d
term
memory
mary
pn
c
us,
wntc
estruct1Ve
as
e
t t. f
15
,
th c con ens o a memory word.
5. What is the difference between RAM and ROM ?
refers. to ra n d.om access memory where both read and write operations ct1n t.1kc
th RA
B tRAM
Solution.
MIS a volatile memory; its contents are lost when power is turned off.
e
u
Pace.
1
ROM ref~rs to read only memory where only read operation can take place. The ROM is a
non-volatile memory.
Both RAM and ROM are parts of the primary memory.
What is Cache memory? Why is it considered crucial for a microprocessor's performance?
6
Solution. Cach e memory is a special high-speed memory that stores most recently used d a ta in
o rd er to speed u p the process of instruction execution. A cache can speed up d a ta re trieval
b ecau se recently used data is likely to be used again by the computer.
7. Wh at is the role of CPU of a mobile system ?
Solution. A mobile system has to cater to a variety of operations and applications and its CPU h as to
m an age all these. Thus th e CPU of a mobile system has many sub-processors that h elp it control and
manage diverse applications. The CPU of a mobile manages all these types of applications and operations :
~ M an ages communications while connecting to radio transceivers and SIM.
~
Manages audio through ADC (analog to digital converter) and DAC (digital to analog converter).
~ M anages display and touch sensitive sensors and in terface.
~ Works in tandem w ith memory and storage.
8.
Wha t are various categories of software ?
Solution. There are broadly two categories of software :
1. System Software. This type of software controls internal computer operations. The system
software can further be classified in two categories :
(i) Operating System. An operating system is a program which acts as an interface between a user
and the hardware.
(ii)
Language Processor. This program is responsible for converting an HLL code (High Level
Language code) into machine understandable code.
2. Application Software. An application software is the set of programs necessary to carry out
operations for a specified application.
9.
What is the difference between an interpreter and a compiler ?
nd
Solution. An interpreter converts an HLL program into machine language line by line ath
simultaneously executes the converted line. Also, an interpreter must always be present in e
memory along with the program for its execution. If an error occurs in a line, the line is displayed
and interpreter does not proceed unless the error is rectified.
th
A compiler converts an HLL program in machine language in one go. If there are errors in e
program, it gives the error list along with the line numbers. Once the errors are removed, error-free
obj<.> ct code is made available and after this compiler is no more needed m the memory.
20
Path Wala
7 Why is 11 requm~d ?
hat pertains to one application.
.
Wl,nt is nppl1cnt1011 ,oftwa11:.
h rout
ftw ire 1s a software t
• ·
stem software cannot carry out t
"olut1on. Apphcat1on so (
.
. required because sy
.
I' t' n software can easily do.
Appli ca tion so ft ware is
Performed by the user which app ica io
1· t· n software comes in various categon
'
To perform various kind s of act1.v1·r,es, the app ,ca io
•
10
n
(i) Packages
(ii) Utilities
(iii) Business Software
( · ) Developer Tools.
h ,L
. beIow. Study each stalt:.ment and eternune w tc,,
. are given
Fiveivstatements about interpreters and compilers
d
·
11 . of them hold true for a compiler or for an interpreter.
(') takes one statement at a time and executes it.
generates an error report at the end of translation of the whole program.
(iii) stops the translatzon
{,' st error is encountered.
. process as soon as ti Ie ;Ir
(iv) slows speed of execution of program loops.
(v) translates the entire program in one go.
u\
Solution. Interpreter : (i), (iii), (iv) ;
q
Compiler : (ii), (v)
uid e Ii n es Io NCERT Que s Ii on s
[NCERT Chapter 1]
1. Name the software required to make a computer functional. Write down its two primary services.
Ans. Operating System. Two of its primary services are : managing CPU and managing primary
memory.
2. How does the computer understand a program written in high level language ?
Ans. The program written in high level language is first converted/translated into machine language
by a language processor, which is then handed over to a computer. Thus, the computer is able to
understand the programs written in high level language.
3. Why is the execution time of the machine code less than that of source code ?
Ans. The translated machine code runs fast (faster execution time) as now the computer does not
requ,ire any type of conversion to run it ; unlike source code which requires conversion into
object/machine code before it can be executed.
4. What is the need of RAM ? How does it differ from ROM ?
Ans. The RAM is needed for the smooth running of a computer's operations as it provides memory
for reading as well writing; its contents can be modified as and when required. ROM, on the other
instructions
stores somefrom
hand,
ROM. which are permanent. ROM cannot be written onto. One can only
read instructions
Thus RAM along with ROM, is required for the smooth functioning of a computer system.
5. What is the need for secondary memory ?
Ans. The primary memory holds the data and instructions only during processing and alter that, it
gets erased. One cannot store data and instructions permanently on RAM.
·
·
To permanently store data and instructions the secondary
memory 1s reqmred.
,
Path Wala
SYSTEM OVERVIEW
Ch opter I . COMPUTER
21
p11il'r co1111111111icate u•ith ench otlzer ?
6. Ht>W rio d/fcrent conrpo11rnto:; of the co111
ects the
r com mun icate thro ugh the bus whic h conn
Ans. Different com pon ents of a com pute
m.
functional com pon ents of a com pute r syste
do the following:
13. Nn111c the input or outp ut device used to
(n) To output audio
(b) To enter textual data
(c) To make hard copy of a text file
(d) To display the data or information
(e) To enter audio-based command
(f) To build 3D models
in enter ing data
(g) To assist a visually-impaired indiv idual
(e) MIC
(d) mon itor
(c) prin ter
(b) keyb oard
Ans. (a) spea ker
(g) Braille Keyboard
(f) 3D prin ter
:
n, programming tool) of the following software
14. Ide11tifiJ the category (system, applicatio
(d) Text editor
(c) Ubu ntu
(b) Assembler
(a) Com pile r
g tool
are (c) system software (d) prog ram min
Ans. (a) syst em soft ware (b) syst em softw
GL OS SA RY
Bit
A binar y digit.
Byte
A grou p of eight bits.
AW
Application
Software
Compiler
Operating System
CPU
Mem ory
EPROM
arithmetic and logic a l operations.
Arith metic Logic Unit that carries out
of a specified appli catio n.
Software perta ining to the operations
ts all the errors along
mach ine langu age in one go and repor
Prog ram that converts HLL prog ram into
with their line numbers.
en a user and the hardw are.
Prog ram which acts as an interface betwe
entire opera tion.
the given process and supervises the
Cent ral Processing Unit that carries out
uter.
to store data and progr ams in a comp
An organ ized collection ,of cells used
ble and electrically
ory, a device that is ultraviolet-erasa
Erasable prog ramm able read -only mem
repro gram mabl e.
own programs and data.
PROM programmer, you can bum in your
Programmable read-only memory. With a
read the contents of
a read-write mem ory because you can
Random-access memory. It is also called
RAM
nts into it.
a memory locat ion or write new conte
e storage of programs
Mom ) This device provides non-v olatil
Read-only mem ory. (ROM Rymes with
ROM
locat ion by supplying its address.
and data . You can access any memory
tion of a comp uter system.
Set of progr ams that govern the opera
Softw are
mach ine understandable form.
converts a high level langu age code into
Language Processor Software that
operations.
Software that controls internal comp uter
System Softw are
perfo rming housekeeping functions.
A software that assists the comp uter by
y Softw are
PROM
Utilit
OMPUTER
22
I t~ E WI rt I
/THON
X:
Path Wala
.
t
t .
Wh d
1. Briefly explain the basic architecture of a computer.
at oes compu er tnpu consist of?
t unit?· What is its significance?
·
2. What do you understan db Y mpu
· th e fu nc t·10n o f CPU in a computer system ? What are its subunits ?
3. What 1s
•
are per forme d by the control unit ?· Can we call it the control centre of computer
4. What functions
.
.
_
system ? Why ?
does ALU
unit
which
not,
If
?
urut
independent
an
it
Is
?
ALU
the
by
performed
are
functions
What
_
5
work in coordination with ?
6. Distinguish between CPU and ALU.
7. What is the function of output unit in a computer system ? Give examples of some output devices.
8. What role does memory play in the functioning of computer system ?
9. Define each of the following :
(a) byte
(b) kilobyte
(c) megabyte
(d) gigabyte
(e) terabyte.
10. What is the meaning of the term volatile primary memory ? What can be done to overcome the
problems of volatility ?
11. Distinguish between internal and external memory.
12. What is the role of memory in a computer functioning ? What types of memory does the computer work
with?
13. What are RAM and ROM ? How are they alike ? How are they different ? What are EEROM, PROM and
EPROM?
14. What is cache memory ? How is it useful ?
15. What are major functional components of a mobile system ?
16. Draw a block diagram depicting organization of a mobile system.
17. What is the role of power management unit in a mobile system ?
18. What does the communication processor do ?
19. What is the role of application processing unit in a mobile system ?
20. How does display subsystem of a mobile system work ?
21. What are different categories of software ? Give examples.
22. ~at is system softw~~e ? What role does it play in the functioning of the computer ?
23. Discuss the role of utility software in the context of computer perform
ance.
.
· th e importance
24 • What 1s
of an OS ?
f
25. How are software libraries useful ? Name some softwa l'b .
re 1 ranes o Python.
.
26 H
?
ow is system software different from application soft~
.
are .
27. What is the utility of these software ?
(i) disk fragmentor
(ii) backup software.
.
28. To run your computer system, what t es of s f
O
tware are necessary ? What role does each type play 111
YP
computer's functioning ?