Upload
kingsley-sayyd-idiagbor
View
19
Download
0
Tags:
Embed Size (px)
DESCRIPTION
Introduction to Computer Appreciation for beginning students at Elementary grades.
Citation preview
Basic Computer Science for
Beginners
By
Kingsley Idiagbor, B.Sc(Hons), PGDCs
December 2002
1
COMPUTERDEFINITION: Computer is an electronic machine used for processing data, store and produce an output to the userDATA: Data is the raw information that is fed into the computer.Data comes in three forms: letters (like a,b,c..)numerals (such as 1,2,3...) and special characters (e.g. $, @,/ ..)INPUT: Input is the process of feeding data into the computer.OUTPUT: is the processed data that is communicated to the user. The output is also
CATEGORIES OF COMPUTER
There are four major categories of computer:
Microcomputers: These are computer systems
that have the microprocessor in one case.They
are further subdivided into palmtop,
notebook, laptop and desktop computers.
2
Input Process Output
Storage
2. Minicomputers: These are more powerful than the
microcomputers and can support a number of users
performing different tasks. Most powerful mini-computers
are called super mini-computers
3. Mainframe: They are large systems that can
handle hundreds of users. They store large amounts
of data and process transactions at high rate.
Mainframes require several rooms to store.
4. Super-computers: They are the most
powerful category of computers and also the most
expensive. They are used for such applications as
weather forecasting, engineering designs and testing,
space exploration and other tasks, which require long
and complex calculations.
TYPES OF COMPUTER
We have three different kinds of computers:
i) Analog computers;
ii) Digital computers and
iii) Hybrid computers
Analog computers
These are devices that measure one form of
physical quantities or another like temperature, pressure,
speed and so on. Examples of analog computers are
thermometer, barometer, speedometer and hygrometer
3
Digital computers:These are devices that are used for
counting. Examples include adding machine, billing machine, electronic wrist-watch and calculator
Hybrid computersThese devices combine the functions of
measuring physical quantities as well as counting.
Electronic computers like desktop computers and
notebooks are examples of hybrid computers
PARTS OF A COMPUTERThere are four major parts of a computer:1. Monitor;2. System Unit (which contains the CPU,hard
disks & others)3. Disk drive (provides slot for diskettes)
4. Keyboard
Monitor
System Unit
Disk drive
Keyboard
4
PERIPHERALSThese are those external devices that
must be attached to the System unit for them to work.Examples of Peripherals:i) mouse;ii) light pen;iii) printer;iv) plotter;v) modem (modulator-demodulator);vi) UPS (Uninterruptible power supply);vii) scanner;viii)telephone;ix) data projectors;x) microphoneamong several others. Some peripherals, not a major part, are becoming indispensable features of a modern PC (Personal Computer). Examples are the mouse, scanner and printer
HARDWAREThis is the physical component of the computer which we can see and touch
Hardware is made up of four types of devices or units. These include: input devices, processing devices, output devices and storage devices.
INPUT DEVICESInput devices are those devices that are used for feeding in data into the computer.Enlisted below are various input devices:i) keyboardii) mouse;iii) scanner
5
iv) light pen;v) joystick (for playing computer games);vi) voice input;vii) touch screens;viii) trackball;PROCESSING DEVICES
These are units that process data from one form to another. The CPU (central processing unit) which is generally regarded as the 'heart' or the 'brain' of the computer, is a major processing device. Another example is the Modem (modulator-Demodulator) which is processes data for communication purpose. The modem enables the computer to dial a telephone or access the INTERNET (more on this later on the course) by dial-up methodOUTPUT DEVICES They are devices that computer uses to produce output (information)or the unit that is used to communicate with the user. They may include:a) monitor;b) printer;c) data projectors;d) plotters;e) computer output microfilm;f) voice output (such as we find in Robot technology)
6
STORAGE DEVICESStorage is the fourth and final
operation in the information processing cycle (earlier mentioned). As the name implies, storage devices are those devices used for storing data and programs for later use. We have primary storage (main memory inside the system unit) and the secondary storage devices. The latter is sometimes calledAuxillary storage. In the section that follows, we are going to look at some of them in detail:
MONITORMonitor is the part of the computer that looks like television set. It is variously called as CRT (Cathode Ray tube), VDU (Visual display unit), Screen or just Display.
The output that is displayed on the computer cannot be touched, as it were, and is called soft copy output.Pixel: also called 'picture element’ are the individual dots that make up the text or graphic and can be illuminated. The greater the number of pixels, the better the screen resolution.Resolution: This is the clarity of a monitor and is determined by the number of pixels that can be illuminated.
TYPES OF MONITORSWe have two major kinds of monitors: monochrome monitors and colour monitorsMonochrome Monitors: They are computer terminals that display a single colour such
7
as amber, green or white on a black background; or black
characters against white backgroundColour MonitorsThey are more expensive than the monochrome
monitors and are more desirable because
colour enables users to more easily read and
understand the information on the screen.
Several Graphic standards have been developed and they include:CGA: (Colour Graphics Adapter);EGA (Enhanced Graphics Adapter)VGA (Video Graphics Array)SVGA (Super Video Graphics Array)
Each standard provides for a different number of pixels and colours and offer even higher resolution screens.
With the development of mobile
computing in the form of truly portable
computers that could be conveniently carried
by hand or in a briefcase, came a need for an
output display that was equally portable.
Today, we have what we call the Flat panel
Monitors that are actually LCD (stands for
Liquid Crystal Display) and plasma
screens.There are also the TFT (stands for
8
thin-film transistors) monitors that makes
use of LED (Light emitting diodes).
Printers
Printers are very important peripheral
in that they produce hard copy output that
the user can carry about unlike the soft copy
output from monitors.
How are Printers Classified?
Printers can be classified by how they
transfer characters from the printer to the
paper. This is either by impact or non-impact
Impact printers
These transfer the image onto the paper by
some type of printing mechanism striking the
paper, ribbon, and character together.
Examples of impact printers include:
a) dot-matrix printer
b) daisy wheel printer
c) chain printer
d) band printer
Non-Impact printers
9
There are also a variety of non-impact
printers. These include ink-jet printer,
thermal printer and page printers like the
laser jet printer.
Choosing a Printer
Besides understanding the features and
capabilities of the various types of printers
that are available, one must consider other
factors before choosing a printer. Such
factors include how much output will be
produced, the speed as well as the quality of
the text and graphics. Laser-jet is very
desirable for printing heavily text documents
while ink-jet printer is the best bet for
graphics intensive documents.
Terms associated with Printers
DQ Draft quality
NLQ Near Letter quality
LQ Letter quality
CPS Characters per second
PPM Papers per minute
BRIEF HISTORY OF COMPUTERS
Computing has a long history and started with man’s search for the best method of easy counting and manipulation of items
1
and number of materials and other resources. The Chinese and the Ancient Babylonians made use of the Abacus. During the renaissance period however, notable scientists like Blasé Pascal, James-Marie Jacquard, and Charles Babbage devised better counting devices. We had the punched cards by Jacquard, Herman Hollerith’s tabulating machine that eased the 1890 American census and became the older cousin of the IBM computers. The first electronic computer was the ENIAC and was developed by IBM in the year 1946. They were very large and produced large amount of heat because of the use of vacuum tubes. They were the first generation computers. The development of transistors gave birth to the second-generation computers, which were not as large and produced less heat. In 1969, Ted Hoff invented IC (Integrated circuit) and together with Gordon Moore developed the 8008 microprocessor in INTEL. Microcomputers were born. In 1975, average person could now purchase personal computers. In 1980, IBM gave Bill Gates of Microsoft Corporation, a contract to come out with an operating system. His MS-DOS and later several releases of ‘Windows’ have changed the face of computing world-over.
INTERNET is the information superhighway that started as ARPANET in late 60s but became popular in the mid 1990s. With the advent of INTERNET came e-commerce, e-mail, virtual research, and teleconferencing. Suffice it to say that the INTERNET is perhaps the greatest gift of computing to man
1
and has changed the way that he views his world.
COMPUTER TIMELINE [summary]
1400 BC Abacus
1800 AD James-Marie JacquardWeaving1 loom machine /cards
Fig: Jacquard’s punched cards
1890 Charles Babbage [generally
regarded as Father of computer]
analytical engine
1890.1924 Herman Hollerith’s
tabulating machine
1937 Atanasoff-Berry-Computer [ABC]
1946 von Neumann & Mauchley –ENIAC
1952 Grace Hopper programs computer
using symbolic code. Note that
1
Fig: Charles Babbage’s Analytical Engine
Ada Lovelace, a woman, was the
first programmer
1957 FORTRAN programming language
1958 Computers built with transistors
1969 Ted Hoff of Intel developed a
microprocessor codenamed Intel
4004;
ARPANET-forerunner of INTERNET
1970 4th generation computers
1975 MITS-the first commercial PC
1976 Steve Jobs & Steve Wozniak built
the first Apple ® computer
1980 Bill Gates –MS-DOS
1981 IBM PC introduced
1983 Mitch Kapor –Lotus 1-2-3
1984 Apple introduces Mac computers
1989 Intel 80486 microprocessor for
486 computers
1990 Microsoft released Windows 3.0
1995 Microsoft released Windows 95 w/
FAT-32 addressing system &
Internet browser in one
1995 Pentium technology
1
1996 More domain registration for
INTERNET
1997 Nanotechnology & miniaturization
of computers
1998 Microsoft released Windows 98
April 8, 2023
What is a program?
Program is a set of instructions that are
fed into a computer to carry out a task.
The computer is lifeless and you can really
not do any thing without programs. We can type
our letters with the computer because of a program
that makes the computer to allow us to do so. The
program could be a simple one like instructing the
computer to add two numbers together or could be
a complex one like forecasting what the weather
would be like in Calabar tomorrow.
Programming Language
If I want you to do something for me, that is an
instruction, isn’t it? You cannot actually carry out
the instruction if you did not understand my
1
language. It is so with the computer, too. To be
able to write a program, the instructions should be
written in a language that the computer can
understand easily. Such a language is called a
programming language.
Examples of programming language
1. BASIC (which stands for Beginners All-
purpose Symbolic Instruction Code)
2. FORTRAN (Formula Translator)
3. COBOL (Common Business Oriented
Language)
4. ADA
5. Pascal
6. C
7. C + + (pronounced C plus plus)
8. HTML (Hyper Text Mark-up Language –
used for web page authoring in the
INTERNET)
9. JAVA
10. ALGOL (Algorithmic Language)
1
There are many other languages that can be used
for writing programs. These are just a few of them.
SOFTWARE
Software is the collection of programs in the
computer, which we can see at times but cannot
touch.
Types of software
There are three major types of software, namely:
a) System software;
b) Application software and
c) Utility software
System software
These are programs that control the operations of
any computer. Some of these operations include
starting up the computer (booting), loading,
executing (that is carrying out instructions).
1
System software includes operating system and
language translators or what we call compilers.
Some operating systems include:
a) MS-DOS [Microsoft Disk Operating System]
b) WFWG (Windows [3.11] For Work Groups)
c) Windows 95 or 98
d) Windows 2000 Professional
e) Windows ME (Millennium Edition)
f) Windows XP (Windows Experience)
Application software:
These are programs that are designed to carry out
specific tasks for us. Application software is
sometimes referred to as packages. Again, there
are different types of application software namely:
a) Word-processing : This software enables us
to type letters, memos and documents. E.g.
MSWord, WordPerfect, Lotus AmiPro,
WordStar, Write, MultiWrite, Windows
WordPad and so on.
1
b) Spreadsheet: We use spreadsheets to
manage tables, prepare financial reports or
calculate scores for an examination report
sheet in the school. E.g. MSExcel, FoxPro,
LOTUS 1-2-3
c) Computer Graphic software: This
makes it possible for the user to manipulate
charts, pictures and several beautiful
designs with the computer. E.g. COREL
DRAW 10, ADOBE PhotoShop, ADOBE
Illustrator, PRINTMASTER Gold Deluxe and
so on.
d) Database: This software allows the user
to enter data such as the names of students
in a school with their ages and classes and
enables the user to retrieve such information
at a later date.
UTILITY SOFTWARE
This software takes care of the management and
the security of the files inside the computer. We
1
have Anti-virus packages like Dr Solomon Virus
Scan, McAfee, NDD, Norton Utilities. There are
also utility software that clears up the hard disks of
nonsense files when the disk is nearly full.
Central Processing Unit
This is the main control unit of the computer. It can
be said to be the brain of the computer or the heart
and so on.
Parts of the CPU
The CPU consists of the control unit and the ALU
(which stands for Arithmetic/Logic unit). These two
work together using the program (instructions fed in
by the programmer, you remember) and the data
that are stored in the main memory to perform.
Therefore the parts of the CPU include
a) control unit;
b) ALU and
c) Main memory
1
Main Memory
The main memory stores three items. These
include:
a) the operating system e.g. Windows 95/98 or
windows XP that directs and monitors the
activities of the computer equipment;
b) the application software that will direct the
work that is to be done by the user whether
it to type a letter or design a card;
c) the data, which is currently being processed
by the application software
What is Byte?
What is Memory address?
In the main memory, each location is called a byte.
Just as a house on a street has a unique address
that shows the location on the street, each byte in
the main memory of a computer has an address
that indicates its location in memory.
2
The number that shows the location of a
byte in memory is called a memory address
Bit: is short form of binary digit. The computer
basically understands only two things 1 and 0. This
in Mathematics is called number base two or binary
scale.
Nibble: 4 bits make up a nibble
Byte: 8 bits make up a byte or
2 nibbles make a byte
1024 bytes equal 1 kilobyte (KB) (However, this is
often abbreviated to 1000 bytes, so we say that
1kB is equal to 1000 bytes instead of 1024 bytes)
The size of main memory is normally measured in
kilobytes. When memory exceeds 1000kB (1
million bytes), it is referred to in megabytes (MB).
1000MB (that is one billion bytes) then it is called
Gigabyte.
Types of memory
1. RAM – This stands for Random Access
Memory. This is volatile in that whenever
2
there is a power outage, everything stored in
the memory is wiped off. This is where the
computer stores the program that it loads
during booting (later on this course) and also
the place that the computer temporarily
stores the data that is being fed in, before
you save the work. Saving is the act of
transferring the work that you are doing to
the hard disk where you can retrieve at a
later time.
2. ROM: This stands for read-only
memory. This is made up of all the
instructions that were stored in by the
makers of the computer. These instructions
enable the system (computer is also called
system) to start up or boot, for example.
ROM cannot be altered (changed) or
modified like the RAM.
3. PROM: This stands for programmable
read-only memory. Here, you can be
2
allowed to program what you want the
computer to do but once this is done, you
cannot again change anything. Note that it is
only in the PROM that this programming can
be allowed not the ROM.
4. EPROM: This stands for Erasable
Programmable read-only memory
5. EEPROM: This stands for Electronically
Erasable Programmable read-only memory
What is booting?
This is the initial start-up procedure of the
computer. When you put on the computer, it tests
itself and loads the operating system into the main
memory of the computer. When it is doing this, the
computer is not ready for use yet and is said to be
booting.
Cold Booting
This occurs when the computer is switched on with
the plugs correctly wedged into the socket in the
mains. As a general rule, you put on the CPU first
2
before the monitor. When you finish with the
computer, i.e. at shutdown, you put off the monitor
first before the CPU.
Warm Booting
Warm booting means to reset the computer. In this
case, one does not have to put off the computer
before switching it on again. To warm boot, three
keys on the keyboard have to be pressed together.
These keys are Control (Ctrl) key, Alternate (Alt)
key and the Delete key (Del)..
It is suggested that using your left hands (for
a right handed person) press CTRL and ALT keys
together, while at the same time you use the right
hand to hit the DEL key. When you do this, you are
warm booting the computer.
AUXILIARY STORAGE DEVICES
These are devices that store data or the output
from the computer for later use.
Generally, we have the rigid and the removable
auxiliary storage devices
2
Types of Auxiliary Storage devices
1. Magnetic disk storage ;
2. Magnetic tape ;
3. Optical disks ; e.g. CD-ROM (Compact disk-
read-only memory) ,CD-i(Compact disk-
interactive), CD-R (Compact disk-
recordable) , CD-RW (Compact disk-
rewritable)
4. solid-state devices ;
5. Mass storage devices and
6. Special-purpose storage devices , e.g. smart
cards and optical cards
Of these types of storage devices, we will discuss
only the magnetic disk storage. It is the most widely
used storage medium for all types of computers.
Diskettes
The removable type is called the diskette. Since
they are thin and flexible, they are sometimes
2
called floppy disks or simply, floppies. They are
convenient, reliable and inexpensive.
There are two sizes of diskettes: 3½” floppy
disk and 5¼” floppy.
2
Care of diskettes
1. They should be prevented from direct
sunlight;
2. Heavy objects should not be placed on top
of diskettes;
3. Do not expose diskettes to hot places or
high temperatures;
4. Avoid touching the magnetic medium with
bare hands;
2
5. Do not press the diskettes with your biro pen
or pencil when writing on the label. That
explains why felt pens are recommended.
6. Avoid bringing diskettes close to magnets or
magnetic materials;
7. They should not be brought near dust,
smoke or water
Hard Disks
This type of magnetic disk storage is rigid and is
fixed inside the system unit. Hard disk is
completely sealed and therefore is less prone to
damage. Example is Winchester® disk, Western
Digital® disk, Maxtor® disk and Seagate® disk.
The hard disk itself consists of round metal
platters on which the data are stored and the read-
write head, which is used to access the data that is
sought.
The storage capacity of hard disks is
measured in megabytes and more recently
gigabytes (that is millions and billions of
2
characters) of storage. This is just like you have
60-leave or 80-leave notebooks that will store more
notes than the 40-leave notebooks.
We also have removable hard disks
especially in some notebook computers and these
are used to ensure higher security of the stored
data. There are also hard cards. The hard card is a
circuit board that has a hard disk built onto it. They
provide an easy way to expand the storage
capacity of a personal computer
Protecting data stored on a disk
Regardless of whether you are using floppy disk or
hard disks, you must have to protect the data that
you store on the disk from being lost. The disk
storage is re-usable since the stored data may be
overwritten and replaced by new ones. This is
clearly a desirable feature because we are afforded
the privilege of replacing or removing unwanted
files. However, it also poses the problem and
possibility of accidentally removing or replacing the
2
file that we wanted to keep. Therefore, to protect
programs and data stored on disks, we may:
a) Write-protect the diskette:
This is done by using the write-protect
notch that is located at the lower side of
the diskette. So, to prevent writing to a
diskette, you will have to move a plastic
cover to open the window. If the write-
protect notch is closed however it means
that the drive can write or copy
something on the diskette. Once again, if
the window is open, the drive will not
write on the diskette or floppy disk.
b) Back-up storage: Another good
way to protect our programs or data
stored on disks is by creating back-up
storage. This simply means creating a
copy of important programs and data on
one diskette to another diskette. The
3
diskette is equally a convenient medium
that is used to back up the data stored
on a hard disk of a personal computer.
Today, we now have recordable and
rewritable compact disks that can store
the entire contents of a hard disk as a
back-up storage. This is made possible
by the use of CD-Writers.
COMPUTER VIRUS
A computer virus is a computer code or
program that is capable of replicating itself and
transferring itself from one computer system to
another. Usually, virus can do such things as
change programs or destroy data. They may even
at times format the entire hard disk or blow up a
monitor or disable a printer.
When the host program (that is the program
with the virus) is shared, the virus is spread. As the
host program is copied to friends through diskettes,
the INTERNET, bulletin boards and other usual
3
channels, the virus is also copied along. It infects
the software with which it comes in contact.
They are not detected immediately. Some of
them are like time bombs waiting for particular date
to do their havoc. People who copy the host
software are unaware that the virus exist because it
is coded in such a way as to hide from computer
users for weeks or even months. There are over
9000 viruses known and continue to increase by
day and with the advent of the INTERNET even by
the minute. Major kinds of computer virus include
Boot sector viruses (that prevent the computer from
booting properly), anti-CMOS viruses and Trojan
horses.
Examples of computer virus
December 13 Polyboot A eek80 virus
Black Jesus WM.opey97
Howlen Croween B Klein
Jerusalem virus Holy Moses
3
To neutralize the codes of the viruses, we use the
antiviruses such as Dr Solomon AntiVirus kit,
Norton AntiVirus, McAfee Virus Scan among
others. Antiviruses have to be regularly updated if
they are to be effective.
HOW TO AVOID COMPUTER VIRUS
These are some techniques to at least minimize
viruses and their damaging effects:
The computer should be warm booted when
switching suspicious programs or
applications.
Write-protect your diskettes when they are
to be inserted into suspicious computer
systems
Always use Antivirus to scan any suspicious
diskettes before opening any file inside
them.
In using the INTERNET and bulletin board
service, open e-mail accounts with servers
3
that provide antivirus software that will scan
all incoming mails.
Do not open or download any e-mail
attachments from unknown sources until
they are scanned.
Even when these tips are followed, they cannot be
total guarantee that your system or diskette could
be virus-free when you engage in swapping (that is
copying software). There fore the best method is to
perhaps avoid swapping. Use only registered and
licensed software and avoid tolerating diskettes
from unknown sources from being inserted into
your system.
3
NETWORK
When two or more computers are
connected together, they are said to
form a network.
For computers to ‘see’ each other on a
network, they have to follow the same
set of rules, commands or
configurations called protocol
Examples of protocols:
a) FTP File transfer protocol
b) TCP/IP Transfer control
protocol/Internet or
Intranet protocol
c) NetBEUI British standard
protocol
d) WAP Wireless Applications
protocol
e) HTTP hyper text transfer
3
protocol.
Types of Network
There are two major kinds of network
based on the geographical distribution
of the computers:
a) Local Area Network (LAN)
and
b) Wide Area Network (WAN)
Local Area Network: This is when the
computers are connected together
within the same area such as building
or campus
Wide Area Network: In this type of
network, computers connected together
are in wide geographical area like
different cities or even countries.
The INTERNET is a good example of WAN.
What is Server?
3
What is Client?
Networking is very advantageous
for file sharing as well as
resource sharing.
When computers are networked, you
wouldn’t have to buy separate printers
for each of them. All you have to do
is buy a single printer for all of
them to share. Note that they have to
have the same protocol, which is the
set of rules and regulations governing
the exchange of information between
computers in a network.
Now, a server is the network control
unit that is dedicated to handling the
communicating needs of the other
computers in a network. These other
computers are referred to as clients.
Whatever is to be shared among the
computers in such a network, say, a
3
printer has to be connected to the
server. Using LAN, all the computers
and the server can use the printer.
In a network, communication
channels are very essential. Wires and
cables are used, although wireless
systems such as light beams, radio
waves or carrier-connect radio are now
prevalent. VSAT (very small aperture
terminals) has largely improved the
efficiency of Wide Area networks in
both Intranet and INTERNET access.
NETWORK TOPOLOGY
Network topology describes the
configuration or physical layout of
the equipment (such as computers and
peripherals) in a communications
network.
Types
a) star network
3
b) bus network
c) ring network
Gateway: is a combination of both
hardware and software that allow users
on one network to access the resources
on a different type of network.
Bridge: is a combination of hardware
and software that is used to connect
similar networks.
Nodes: Devices connected to a
network, such as terminals, printers
or other computers are referred to as
nodes.
Hub: This is a device that connects
all the workstations or client
computers in a network to the server.
We have 9- port, 16-port hubs and so
on.
3
ADVANCED ESSAYS
1800 ADJacquard's Punched Cards
4
1800 ADJacquard’s Punched Cards In the early 1800s, a French silk weaver called Joseph-Marie Jacquard invented a way of automatically controlling the warp and weft threads on a silk loom by recording patterns of holes in a string of cards. In the years to come, variations on Jacquard’s punched cards would find a variety of uses, including representing the music to be played by automated pianos and the storing of programs for computers
IBM 80-column punched card format. See also:Charles Babbage’s Analytical Engine & Herman Hollerith’s tabulating machines
1890 ADHerman Hollerith's Tabulating Machines
4
It is often said that necessity is the mother of invention, and this was certainly true in the case of the American census. Following the population trends established by previous surveys, it was estimated that the census of 1890 would be required to handle data from more than 62 million Americans.
In addition to being prohibitively expensive, the existing system of making tally marks in small squares on rolls of paper and then adding the marks together by hand was extremely time consuming. In fact it was determined that, if the system remained unchanged, there was no chance of collating the data from the 1890 census into any useful form until well after the 1900 census had taken place, by which time the 1890 data would be of little value.
a
The solution to this problem was developed during the 1880s by an American inventor called Herman Hollerith, whose idea it was to use Jacquard's punched cards to represent the census data, and to then read and collate this data using an automatic machine. a
4
While he was a lecturer at MIT, Hollerith developed a simple prototype which employed cards he punched using a tram conductor's ticket punch, where each card was intended to contain the data associated with a particular individual.
From this prototype, he evolved a mechanism that could read the presence or absence of holes in the cards by using spring-mounted nails that passed through the holes to make electrical connections.
Herman HollerithCopyright (c) 1997. Maxfield & Montrose Interactive Inc.
a
Hollerith's final system included an automatic electrical tabulating machine with a large number of clock-like counters that accumulated the results. By means of switches, operators could instruct the machine to examine each card for certain characteristics, such as profession, marital status, number of children, and so on.
4
a
When a card was detected that met the specified criteria, an electrically controlled sorting mechanism could gather those cards into a separate container. Thus, for the first time it was possible to extract information such as the number of engineers living in a particular state who owned their own house and were married with two children. Although this may not tickle your fancy, having this capability was sufficient to drive the statisticians of the time into a frenzy of excitement and data collation.
In addition to solving the census problem, Hollerith's machines proved themselves to be extremely useful for a wide variety of statistical applications, and some of the techniques they used were to be significant in the development of the digital computer. In February 1924, Hollerith's company changed its name to International Business Machines, or IBM. (See also Hollerith's punched cards.)
a
These notes are abstracted from the book Bebop BYTES Back(An Unconventional Guide to Computers) Copyright Information
4