Computer Basics
A computer is an electronic machine that stores, retrieves
and process data
It cannot think or reason; it can carry out instructions
given to it
Ability to accept, store and execute program makes the
computer an invaluable and all-purpose business tool
Properties of a computer system
Volume of data
Accuracy
Repetitiveness
Complexity
Speed
Many more….
Organization of a computer
Components of a computer system
Six components
Hardware
Software
Data/ Information
Procedures
Humanware / People
Communications
Hardware
Refers to machine or physical equipment
Compromises the electronic and the electromechanical parts
of the computer system
Can be
On-line
Ex. Keyboard, Mouse etc
Off –line
Ex. Printer, Scanner etc.
Software
Instructions that tell the hardware
how to perform a task
Is a sequence of instructions, which directs a computer to
perform certain functions
Categorized as
System Software
Application Software
Data/ Information
Procedures
Descriptions of how things are done
Appear in documentation manual, which contain the guidelines
for using the hardware and software
Humanware
Refers to the persons who design,
program and operate a computer
Categorized as
System Analyst
Programmer
End User
Communications
Becomes an element of the computer system when one computer
system is set up to share data and information electronically with another
computer system.
Computer Generations
Computer Generation
The term “generation” is used to distinguish between varying
hardware technologies.
There are total five computer generations:
First Generation (1942-1955)
Second Generation (1955-1964)
Third Generation (1964-1975)
Fourth Generation (1975-1989)
Fifth Generation (1989-Present)
First Generation (1942-1955)
Too bulky in size, requires large rooms.
Thousands of vacuum tubes were used which consumes and
produces large heat.
Magnetic Drum was used as memory
Punch card was used for I/O
Programs were written in machine language.
Example: UNIVAC I, IBM 650, Mark II etc.
Second Generation (1955-1964)
Made of semiconductor materials (Transistors).
Less power consumption/Production
Use of magnetic core memory and the discovery of magnetic
disk as secondary memory
Transmission of data
using telephone line
Programs are written in higher level language (COBOL,
FORTRAN, ALGOL etc.)
Example: IBM 7030, CDC 1604, RCA 301 etc.
Third Generation (1964-1975)
IC technology was used.
Semiconductor memory was used
More than one user can use it at a time
Huge use of high level language
Transmission of data
using computer system and satellite
Use of monitors
Example: IBM 360/370, PDP-8, GE 600 etc.
Fourth Generation (1975-1989)
Use of VLSI technology
Microprocessor based computer
Huge storage capacity
Use of package program and Object Oriented Programming
Use of interactive graphics
Use of Internet
Example: IBM PC and its clones, Apple II, CRAY-1 etc.
Fifth Generation (1989-Present)
Use of Artificial Intelligence
Will be capable of reasoning, learning, making inferences
and behaving like human.
Use of multiple microprocessor
Use of optical fiber
Use of magnetic bubble as memory
Voice recognition, the ability to understand and obey spoken
words.
Classification of Computer
Classification of Computers
Analog computer
Example: Speedometer, Slide rule operational amplifier etc
Digital Computer
Supercomputers
Mainframe Computers
Minicomputers
Microcomputers, or Personal Computers
Hybrid Computer
Supercomputers
— They
are used for problems requiring complex calculations.
— They
are applied to the solution of very complex and sophisticated scientific
problems and for national security purposes of some advanced nations.
— Because
of their size and expense, supercomputers are relatively rare.
— Supercomputers
are used by universities, government agencies, and large businesses.
— They
are generally used in the mapping of human gnome, forecasting weather etc.
Example: The Cray X-MP
Mainframe Computers
Can support hundreds or thousands of users, handling massive
amounts of input, output and storage.
They provide greater processing speed, greater and high
speed storage , a larger variety of input/output devices, multiprogramming and
time-sharing.
Mainframes are also used as e-commerce servers, handling
transactions over the Internet.
CPU speed: 600 MIPS to 10000 MIPS
Example: UNIVAC 1180, Cyber 170 etc
Minicomputers
They are physically smaller, less expensive and have small
storage capacity compared to mainframe.
They are ideally suited for processing tasks that do not
require access to huge volumes of stored data.
Some of the larger and expensive minicomputers are capable
of supporting a number of terminals in time-shared mode.
CPU speed: 10 to 30 MIPS
Example: IBM S/34, PDP 11 etc
Microcomputers
— Commonly
known as PC, refers to a type of computer system that was designed for use by a
single person.
— Notebook
(laptop) computers are used by people who need the power of a desktop system,
but also portability.
— Handheld
PCs (such as PDAs) lack the power of a desktop or notebook PC, but offer
features for users who need limited functions and small size.
— The
brain of microcomputer is the microprocessor; it is a silicon chip containing
necessary circuits to perform arithmetic/logic operations and to control
input/output operations.
Example: IBM PC, PS/2, Apple Macintosh etc
Number Systems
Common Number Systems
Characteristics of Number Systems
1) The
digits are consecutive.
2) The
number of digits is equal to the size of the base.
3) Zero
is always the first digit.
4) The
base number is never a digit.
5) When
1 is added to the largest digit, a sum of zero and a carry of one results.
Quantities/Counting (1 of 3)
Quantities/Counting (2 of 3)
Quantities/Counting (3 of 3)
Conversion Among Bases
The possibilities:
Quick Example
Decimal to Binary
Decimal to Binary
Technique
Divide by two, keep track of the remainder
First remainder is bit 0 (LSB, least-significant bit)
Second remainder is bit 1 etc.
Example
Decimal to Octal
Decimal to Octal
Technique
Divide by 8
Keep track of the remainder
Example
Decimal to Hexadecimal
Decimal to Hexadecimal
Technique
Divide by 16
Keep track of the remainder
Example
Binary to Decimal
Binary to Decimal
Technique
Multiply each bit by 2n, where n is
the “weight” of the bit
The weight is the position of the bit, starting from 0 on
the right
Add the results
Example
Octal to Decimal
Octal to Decimal
Technique
Multiply each bit by 8n, where n is
the “weight” of the bit
The weight is the position of the bit, starting from 0 on
the right
Add the results
Example
Hexadecimal to Decimal
Hexadecimal to Decimal
Technique
Multiply each bit by 16n, where n
is the “weight” of the bit
The weight is the position of the bit, starting from 0 on
the right
Add the results
Example
Octal to Binary
Octal to Binary
Technique
Convert each octal digit to a 3-bit equivalent binary
representation
Example
Hexadecimal to Binary
Hexadecimal to Binary
Technique
Convert each hexadecimal digit to a 4-bit equivalent binary
representation
Example
Binary to Octal
Binary to Octal
Technique
Group bits in threes, starting on right
Convert to octal digits
Example
Binary to Hexadecimal
Binary to Hexadecimal
Technique
Group bits in fours, starting on right
Convert to hexadecimal digits
Example
Octal to Hexadecimal
Octal to Hexadecimal
Technique
Use binary as an intermediary
Example
Hexadecimal to Octal
Hexadecimal to Octal
Technique
Use binary as an intermediary
Example
Exercise – Convert ...
Exercise – Convert …
• Exercise
– Convert ...
• Exercise
– Convert …
• Binary
Addition
• Two
1-bit values
• Binary
Addition
• Two
n-bit values
– Add
individual bits
– Propagate
carries
– E.g.,
• Multiplication
• Decimal
(just for fun)
• Multiplication
• Binary,
two 1-bit values
• Multiplication
• Binary,
two n-bit values
– As
with decimal values
– E.g.,
• Binary
Subtraction
• Just
like subtraction in any other base
– Minuend 10110
– Subtrahand - 10010
– Difference 00100
• And
when a borrow is needed. Note that the
borrow gives us 2 in the current bit position.
• .
• Binary
Subtraction
• And
more ripple -
• Binary
Subtraction
• But
what happens when we want to do the following:
• Compliments
• Subtraction
in any number system can be accomplished through the use of complements.
• A
complement is a number that is used to represent the negative of a given
number.
• Compliments
• There
are two types of compliments for each number base system.
– Have
the r’s complement
– Have
the (r-1)’s complement
• Base
2 have 2’s complement and 1’s complement
• Complementary
Arithmetic
• 1’s
complement
– Switch
all 0’s to 1’s and 1’s to 0’s
Binary
# 10110011
1’s
complement 01001100
• Complementary
Arithmetic
• 2’s
complement
– Step
1: Find 1’s complement of the number
Binary
# 11000110
1’s
complement 00111001
– Step
2: Add 1 to the 1’s complement
00111001
+ 00000001
00111010
• Operation
with 2’s complement
• Add
4 and -6
• Will
use the 2’s complement of -6 or 1010
– 4
0100
– -6 1010
– 1110
• And
taking the 2’s complement of 1110 get 0001 + 1 = 0010
MEMORY
Memory
Classification of Memory
Memory Capacity
Memory Hierarchy
Storage Evaluation Criteria
Storage capacity
It is the amount of data, which can be stored in the storage
unit.
Higher Capacity is desired.
Access time
This is the time required to locate and retrieve stored data
from the storage unit, in response to a program instruction.
Faster access time is preferred.
Storage Evaluation Criteria
Cost per bit of storage
This is the cost of a storage unit for a given storage
capacity.
Lower cost is desirable.
Random Access
If the time taken to access data from the storage unit is
independent of the location of the data in the storage unit, it is called
random access storage.
Volatile
If the storage unit can retain the data stored in it, even
when the power is turned off or interrupted, it is called non-volatile storage.
If the data stored are lost, when the power is turned off or
interrupted, it is called volatile storage.
Non-volatile storage is desirable.
Primary storage units are volatile and the secondary storage
units are non-volatile.
Cache Memory
System performance suffers when processor waits for data
from slow memory device.
Cache memory is introduced between the CPU and the main
memory.
Cache is a high speed memory for holding recently accessed
data in main memory.
Cache Memory
The amount of cache memory has a tremendous impact on the
computer's speed.
Two types of cache:
Level-1 L1 cache: CPU resident cache
Level-2 L2 cache: Motherboard resident cache.
Primary Memory
Two Types
q Random
Access Memory (RAM).
q Read
Only Memory (ROM)
Random Access Memory
Dynamic RAM
Static RAM
Read Only Memory
Use of ROM
Classification of ROM
ROM(Strict ROM)
Programmable ROM
Erasable Programmable ROM
Electrically Erasable Programmable ROM
Electrically Alterable ROM
Ø A
type of EEPROM that can be modified one bit at a time.
Ø Writing
is a very slow process and requires higher voltage (usually around 12V) than is
used for read access.
Flash Memory
Why ROM?
THANK YOU
Secondary Memory
Secondary Memory
Nonvolatile
Slow compared to primary memory
Less costly & high capacity
Magnetic Storage Devices
Magnetic storage and magnetic recording refers to the
storage of data on a magnetized medium.
Example:
Hard Disk
Floppy Disk
Magnetic Tape
How Data is Organized on a Magnetic Disk
Track
Sector
Cluster
Hard Disk
The hard disk drive is the main storage device within a
computer.
It is where all the applications software and data is kept.
Data stored on a hard disk can be accessed much more quickly
than data stored on a floppy disk.
A hard disk spins between 5,400 to 15,000 RPM inside its
metal casing, which is why it makes that whirring noise.
Storage capacity of a Disk
Storage capacity of a disk
=
No. of recording surfaces(Cylinders) X No. of tracks per surfaces X No. of sectors per track X No. of bytes per sector
Storage capacity of a Disk
Calculate the capacity of a hard disk having 1632 cylinders,
12 tracks, 54 sectors per track.
Speed of a Disk
Seek time
The time it takes to position the head at the track is known
as seek time.
Rotational Delay or Rotational Latency
The time it takes for the beginning of the sector to reach
the desired sector is known as rotational delay.
Access time = Seek + Latency
Transfer rate
The time it takes to transfer the data is known as transfer
time.
Advantages of Hard Disk
Large storage capacity.
Stores and retrieves data much faster than a floppy disk or
CD-ROM.
Data is not lost when you switch off the computer.
Cheap on a cost per megabyte compared to other storage
media.
Hard disks can be replaced and upgraded as necessary.
Can have two hard disks in a machine, one can act as a
mirror of the other and create a back up copy.
Disadvantages of Hard Disk
Hard disks eventually fail which stops the computer from
working.
Regular 'head' crashes can damage the surface of the disk,
leading to loss of data in that sector.
The disk is fixed inside the computer and cannot easily be
transferred to another computer
Floppy Disk
Used to transfer small files between computers and make
backup copies to protect against lost work.
3.5”disk can store up to 1.44 MB of data which is
approximately equivalent to 300 pages of A4 text.
Spins at 300 RPM
Takes 0.2 second to find data
Optical Storage
Optical storage is a term from engineering referring to the
storage of data on an optically readable medium.
Compact Disk Read-Only Memory (CD-ROM)
Digital Versatile Disk Read-Only Memory (DVD-ROM)
CD
A Compact Disc (also known as a CD) is an optical disc used
to store digital data.
The CD, available on the market since late 1982, remains the
standard playback medium for commercial audio recordings to the present day.
Standard CDs have a diameter of 120 mm and can hold up to 80
minutes of audio.
There is also the Mini CD, with diameters ranging from 60 to
80 mm; they can store up to 24 minutes of audio.
Advantages
Data cannot be erased from CD-ROMs.
Small and portable.
Very cheap to produce.
CD-ROMs have a much larger storage capacity than floppy
disks.
CD-R
These disks are blank but have been designed to be written
onto once only.
The 'cd-writer' drive uses a laser to burn onto the spinning
surface of the CD-R media.
Once the pit is burnt it cannot be erased.
CD-RW
'CD Read-Write'.
This technology allows the same area of the disk to be
over-written many times (about a 1000 times).
There are two problems with the CD-RW disks
some drives have a problem reading CD-RW disks that have
been burnt by other manufacturers' drives.
CD-R disks are now so cheap that it is less hassle to simply
use a blank disk!
DVD
DVD (also known as "Digital Versatile Disc" or
"Digital Video Disc") is a popular optical disc storage media format.
Its main uses are video and data storage.
Most DVDs are of the same dimensions as compact discs (CDs)
but store more than six times as much data.
Advantages
Very large storage capacity
Sound and picture quality is excellent which makes them
suitable for video and sound
DVD players can read CD-ROMs.
Flash Memory Stick
Flash is a 'solid state‘ memory i.e. it has no moving parts
unlike magnetic storage devices, nor does it make use of lasers -unlike optical
drives.
It works in a similar way to RAM.
The key difference is that data is retained in Flash memory
even when the power is switched off.
They are now fairly inexpensive.
Advantages
More compact shape.
Operate faster.
Hold much more data.
Have a more durable design.
USB ports appear on almost every current PC and laptop. USB
drives can also operate faster than an optical disc drive, while storing a
larger amount of data in a much smaller space.
Comparison of Primary & Secondary Memory
