Download 1.1 Electronic Computers Then and Now 1.2 Computer Hardware

1.1 Electronic Computers Then and Now
The first electronic computer was built in the late 1930s by Dr.John Atanasoff and
Clifford Berry at Iowa State University in USA. They designed their computer to assist
graduate students in nuclear physics with their mathematical calculations.
The first large-scale, general purpose electronic digital computer, called the ENIAC, was
completed in 1946 at the University of Pennsylvania with funding from the US army.
These early computers used vacuum tubes as their basic electronic component. Today
new generations of computers were considerably smaller, faster, and less expensive than
previous ones.
Using today’s technology, the entire circuitry of a computer processor can be packaged in
a single electronic component called a computer or microprocessor chip. These chips
are installed in watches, PDS’s (Personal Digital Assistance), GPS systems, cameras,
home appliances, automobiles, and of course computers.
Modern computers are categorized according to their size and performance.
Personal computers : Used by a single person
Mainframes: Large , very powerful, real-time transaction processing systems, banking
networks, ATMs reservations systems for airline, motels, etc..
Supercomputers: Largest capacity and fastest computers, used by research laboratories
and computationally number crunching application such as weather forecasting.
The elements of a computer system fall into two major categories: Hardware and
Software. Hardware is the equipment used to perform the necessary computations and
includes the central processing unit(CPU), memories, monitor, keyboard, mouse, printer,
and spiker. Software consist of the programs that enable us to solve problems with
computer by providing it with lists of instruction to perform.
1.2 Computer Hardware
Hardware of a computer consist of the following components:
Main memory
Secondary memory, which includes storage devices such as hard disks,
CDs, DVDs, and flash drives.
Central processing unit.
Input devices, such as keyboards, mouse, touch pads, scanners,
joysticks
Output devices, such as monitors, printers, and speakers.
Memory
Consists of memory cells, which is consist of ordered sequence of storage locations.
Address of a memory cell : the relative position of a memory cell in the computers’s
main memory.
Contents of a memory cell : The information stored in a memory cell , either a
program instruction or data.
Bits and Bytes : Binary refers to a number system based on two numbers, 0 and 1, so
a bit is either a 0 or a 1. Generally there are eight bits to a byte.
Storage and Retrieval of Information in Memory: A computer can either store a
value into a memory interims of binary number representations or retrieve a value
from the memory
Main Memory :Main memory stores programs, data and results. Most computers
have two types of main memory.
Random-Access-Memory(RAM) :Used for temporary storage of programs and data.
Everything in RAM will be lost when the computer is switch is off.
Read-Only-Memory(ROM) : Used for permanently storage of programs and data.
The computer can retrieve, but cannot store, information in ROM, hence its name ,
read-only.
Secondary Storage Devices: These devices are used to store huge amount of
information. These are Hard disk, CDs,DVDs and flash memories.
Hard Disk :Hard disks are attached to their disk drives and coated with a magnetic
material. Each data bit is a magnetized spot on the disc, and the spots are arranged in
concentric circles called tracks. The disc drive read/write head accesses data by
moving across the spinning disk to the correct track and then sensing the spots as they
move by. Hard discs hold from one to several hundred gigaBytes(GB) of data, but
clusters of hard drives that stores data from an entire network may provide as much as
a terabyte(TB) of storage.
Term
Byte
KiloByte
MegaByte
GigaByte
TeraByte
Abbreviation
B
KB
MB
GB
TB
Equivalent to
Comparison to Power of 10
8 Bits
1,024 (bytes)
>10**3
1,048,576(bytes)
>10**6
1,073,751,824(bytes)
>10**9
1,099,511,627,776(bytes)
>10**12
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Main
Memory
Input devices
(Keyboards,
Mouse,
Touch Pads,
Scanner,
Joystick)
Central
Processing
Unit(CPU)
Output
devices
(monitor,
Printer,
Speaker,)
Secondary Storage
(Disk,Falsh Memory, DVD,CD)
Components of a Computer
Optical Drives :For storing and retrieving data on compact discs(CDs) or digital
versatile disks(DVDs) that can be removed from the drive. One CD can hold 680 MB
of data. A DVD uses smaller pits packed in a tighter spiral, allowing storage of 4.7
GB of data one one layer. Some DVDs can hold four layers of data- two on each sidefor a total capacity of 17 GB, sufficient storage for as much as nine hours of studioquality video and multi-channel audio.
Flash Drive(USB)(Universal Serial Bus):Flash drives(stick memory) have no moving
parts and all data transfer is by electronic signal only. Typical USB flash drives store
1 to a few GB of data , but 64 GB drives are also available.
Information stored on a disk is organized into separate collections called files: One
file may contain a C program. Another file may contain the data to be processed by
the program(a data file) or a file may contain a picture information. A file could
contain results generated by a program(an output file).
The names of all files stored on a disk are listed in the disk’s directory. This
directory may be divided into one or more levels of subdirectories or folders.
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Central Processing Unit
The Central Processing Unit(CPU) has two roles.
A)Coordinating Operations of Computer
B)Performing Arithmetic and Logical operations on data.
The CPU follows the instructions contained in a computer program to determine
which operations should be carried out and in what order. The CPU stores the results
in main memory.
The CPU can perform such arithmetic operations as addition, subtraction,
multiplication, and division. The CPU can also compare the contents of two memory
cells and make decision based on the result of that comparison. A CPU’s current
instruction and data values are stored temporarily inside the CPU in special highspeed memory locations called registers(high speed memory location).
Input/Output Devices
We use Input/Output devices to communicate with the computer. They allow us to
enter data for a computation and to observe the results of that computation.
We use a keyboard as an input device and monitor(display screen) as an output
device. A keyboard has keys fro letters, numbers, and punctuation marks plus some
extra keys for performing special functions.
A mouse is an input device used to select an operation.
A monitor provides a temporary display of the information that appears on its screen.
If you want a printed version(hard copy) of some information you must sent that
information to an output device called printer.
Computer Networks
Computers are linked together in networks so they can be communicate with one
another. In a local area network(LAN), computers and other devices in a building are
connected by cables or wireless network, allowing them to share information and
resources such as printers, scanners, and secondary storage devices. A computer that
controls access to a secondary storage devices such as a large hard disk is called a file
server.
A network that links many individual computers and local are networks over a large
geographics area is called a wide area network(WAN). The most well known WAN
is the Internet, a network of university, corporate, government, and public-access
networks. The Internet is designed by the US Defense Department’s 1969 ARPAnet
Project. The most widely used aspect of the internet is the World Wide Web(WWW),
the universe of Internet-accessible resources that are navigable through the use of a
graphical user interface(GUI).
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If you have a computer with a modem, you can connect to the information through a
telephone line or television or fiber-optic cable. A modem(modulator/demodulator)
converts binary computer data into audio tones that can be transmitted to another
computer over a normal telephone circuit. At the computer on th receiving end,
another modem converts the audio tones back to binary data. Today’s modems
transmit over 50,000 or 100,000 bits per second or if you have a digital subscriber
line (ADSL), the associated modem can transmit 1.5 million bits per second.
1.3 Computer Software
Mainly there are two main software groups in a computer. These are Operating
system(OS) and Application software.
Operating System
To make the hardware friendly to the user operating system is used. The collection of
computer programs that control interaction of user and computer hardware is called
Operating System. Most of the operating system are written using C language and has a
lot of sub modules in it. OS manages allocation of computer resources. Usually part of
the OS is stored permanently in a read-only memory (ROM) chip work as a starter of the
operating system is called booting the computer.
Here is a list of some of the operating System’s capabilities.
Communicating with the computer user.
Managing allocation of memory, of processor time, and of other
resources for various task.
Managing Input/Output operations among the user programs and OS.
Accessing data from secondary storage.
Writing data to secondary storage.
Command-Line Interface
UNIX
MS-DOS
VMS
Graphical User Interface
Macintosh OS
Windows
OS/2 Warp
UNIX + X Window System
Widely Used Operating System Families Categorized by User Interface Type
Application Software
Application programs are developed to assist a computer user in accomplishing specific
task. For example , a word-processing application MS Word, WordPerfect, or a
spreadsheet application Lotus or Excel programs or a database management application
such as Access or dBASE systems are well known application programs. User can also
create their own application programs by using any programming language and solve a
specific problem.
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Computer Languages
To solve a given problem using computer, user prefer high-level programming languages.
There are many high-level programming languages are available these days.
Language
FORTRAN
COBOL
LISP
C
Prolog
Ada
Smalltalk
C++
C#
VisualBasic
Java
Application Area
Origin of Name
Scientific
Formula Translation
Business data processing
Common Business Oriented Language
Artificial Intelligence
List Processing
System programming
Predecessor language was named B
Artificial Intelligence
Logic Programming
Real-Time distributed sys. Ada Augusta Byron Collaborated..
GUI
Objects “talk” to one another with message
Support OOP
Incremental modification of C
Support OOP,General purpose
Support OOP,General purpose
Supports web programming
Source file is written by a programmer for the solution of a specific problem. A source
file containing the text of a high-level language program. The software developer creates
this file by using an editor or word processor . Using a compiler this source program is
compiled. During compilation grammar rules are checked.(syntax checking) If the
program is syntactically correct, compiler saves in an object file . Object file consist of
machine language instructions. Using linker program object file is converted into
machine language code which is an executable file and ready to run. Running this file
given problem will be solved.
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