Textbook: History of Computers- From Abacus to Smart Phones | Computer Science for Class 7 PDF Download

 Page 1


Jyoti and Tejas have brought an abacus, 
pictures of old computers, a handmade 
slide rule, a cloth with pretty designs 
and some notes written on sheets of 
paper. Other students are looking on and 
wondering how these articles are related 
to history of computers. 
Simple calculations were done in innovative ways with stones, pebbles and even bones. These 
were called counters. A device with more complicated calculation abilities was the abacus, of 
which we can find many versions.
Abacus – 6
th
 century B. C
Computing Squares and sums by arranging counters
Calculation using fingers
Sieve of Eratosthenes: Finding prime 
numbers in 3
rd
 century B.C
Jyoti: We have gathered history of 
computers right from 3rd century B.C.  
It is very interesting to find what people 
did when there were no computers. 
     Information gathering 
Use of counters to aid calculations: 3
rd 
- 6
th
 century B.C 
The first step for gathering information is to list what you know, what you do not know. Next, gather, consolidate, analyse and organise the 
gathered information. 
1
Aim: In this lesson, you will learn:
- Various devices that have been used for computations in the past.
- Major milestones in development of modern day computers
- Development of Internet, browser and other Internet based applications, 
   games and Linux.
History of Computers: From   
Abacus to Smart phones 8
Moz: We have been using computers for the past 40 years. But the origin of the concepts, algorithms 
and the developments in computations date back to the very early times and cultures.
Tejas: In very early days, when there were no computational devices, people used pebbles, bones 
and the fingers of hands to count and calculate. 
Jyoti: They even used ropes and shapes for some measurements. For example: For assuring a right 
angle, people used 3-4-5 right triangle shape or a rope with 12 evenly spaced knots, which could 
be formed into a 3-4-5 right triangle.
1
Page 2


Jyoti and Tejas have brought an abacus, 
pictures of old computers, a handmade 
slide rule, a cloth with pretty designs 
and some notes written on sheets of 
paper. Other students are looking on and 
wondering how these articles are related 
to history of computers. 
Simple calculations were done in innovative ways with stones, pebbles and even bones. These 
were called counters. A device with more complicated calculation abilities was the abacus, of 
which we can find many versions.
Abacus – 6
th
 century B. C
Computing Squares and sums by arranging counters
Calculation using fingers
Sieve of Eratosthenes: Finding prime 
numbers in 3
rd
 century B.C
Jyoti: We have gathered history of 
computers right from 3rd century B.C.  
It is very interesting to find what people 
did when there were no computers. 
     Information gathering 
Use of counters to aid calculations: 3
rd 
- 6
th
 century B.C 
The first step for gathering information is to list what you know, what you do not know. Next, gather, consolidate, analyse and organise the 
gathered information. 
1
Aim: In this lesson, you will learn:
- Various devices that have been used for computations in the past.
- Major milestones in development of modern day computers
- Development of Internet, browser and other Internet based applications, 
   games and Linux.
History of Computers: From   
Abacus to Smart phones 8
Moz: We have been using computers for the past 40 years. But the origin of the concepts, algorithms 
and the developments in computations date back to the very early times and cultures.
Tejas: In very early days, when there were no computational devices, people used pebbles, bones 
and the fingers of hands to count and calculate. 
Jyoti: They even used ropes and shapes for some measurements. For example: For assuring a right 
angle, people used 3-4-5 right triangle shape or a rope with 12 evenly spaced knots, which could 
be formed into a 3-4-5 right triangle.
1
Explorations of various continents and trading brought in the requirements of precise calculations 
of sea routes, accounting, planetary positions, and navigational tables- 16
th
 century.
Mechanical devices were also developed to assist in tedious and repetitive calculations like 
generating calendars of a year, taxing and trading. 
The Slide rule was used  for landing man on 
the Moon. This was used by NASA engineers 
in 1960s for the Apollo mission.                                      
Napier bones- Numbers 0 to 9 were marked 
on a set of ivory sticks in such a way that 
the product of any number can be found 
by placing the sticks side by side.                                          
Pascaline built by Pascal for his
father who was a tax collector.
Stepped reckoner by
Leibniz using flutes.
Schikard’s 
calculating
clock with gears
Tejas: Early mathematicians around the world such as al-Khwarizmi, Panini, and Euclid developed 
many algorithms. 
Jyoti: Algorism and algorithm stem from Algoritmi, the Latin form of al-Khwarizmi’s name.
Simple devices to aid human calculations- 16th century
Devices with gears and flutes for calculations- 16th-17th century
Jyoti: The first computers were people. This was a job title given to people who did repetitive 
calculations for navigational tables, planetary positions and other such requirements. 
Tejas: Women with mathematical proficiency were often employed for the job. 
Jyoti: I am sure a lot of calculations were involved in building pyramids and Taj Mahal.
Tejas: Of course mathematics and physics knowledge was applied to weave the designs for the 
beautiful old tapestry that we see in many places.
Moz: Good observations. So they started inventing devices for precise calculations and automation 
of certain tasks. One of the important automation which is the Jaquard loom is important in the 
computer history.
Page 3


Jyoti and Tejas have brought an abacus, 
pictures of old computers, a handmade 
slide rule, a cloth with pretty designs 
and some notes written on sheets of 
paper. Other students are looking on and 
wondering how these articles are related 
to history of computers. 
Simple calculations were done in innovative ways with stones, pebbles and even bones. These 
were called counters. A device with more complicated calculation abilities was the abacus, of 
which we can find many versions.
Abacus – 6
th
 century B. C
Computing Squares and sums by arranging counters
Calculation using fingers
Sieve of Eratosthenes: Finding prime 
numbers in 3
rd
 century B.C
Jyoti: We have gathered history of 
computers right from 3rd century B.C.  
It is very interesting to find what people 
did when there were no computers. 
     Information gathering 
Use of counters to aid calculations: 3
rd 
- 6
th
 century B.C 
The first step for gathering information is to list what you know, what you do not know. Next, gather, consolidate, analyse and organise the 
gathered information. 
1
Aim: In this lesson, you will learn:
- Various devices that have been used for computations in the past.
- Major milestones in development of modern day computers
- Development of Internet, browser and other Internet based applications, 
   games and Linux.
History of Computers: From   
Abacus to Smart phones 8
Moz: We have been using computers for the past 40 years. But the origin of the concepts, algorithms 
and the developments in computations date back to the very early times and cultures.
Tejas: In very early days, when there were no computational devices, people used pebbles, bones 
and the fingers of hands to count and calculate. 
Jyoti: They even used ropes and shapes for some measurements. For example: For assuring a right 
angle, people used 3-4-5 right triangle shape or a rope with 12 evenly spaced knots, which could 
be formed into a 3-4-5 right triangle.
1
Explorations of various continents and trading brought in the requirements of precise calculations 
of sea routes, accounting, planetary positions, and navigational tables- 16
th
 century.
Mechanical devices were also developed to assist in tedious and repetitive calculations like 
generating calendars of a year, taxing and trading. 
The Slide rule was used  for landing man on 
the Moon. This was used by NASA engineers 
in 1960s for the Apollo mission.                                      
Napier bones- Numbers 0 to 9 were marked 
on a set of ivory sticks in such a way that 
the product of any number can be found 
by placing the sticks side by side.                                          
Pascaline built by Pascal for his
father who was a tax collector.
Stepped reckoner by
Leibniz using flutes.
Schikard’s 
calculating
clock with gears
Tejas: Early mathematicians around the world such as al-Khwarizmi, Panini, and Euclid developed 
many algorithms. 
Jyoti: Algorism and algorithm stem from Algoritmi, the Latin form of al-Khwarizmi’s name.
Simple devices to aid human calculations- 16th century
Devices with gears and flutes for calculations- 16th-17th century
Jyoti: The first computers were people. This was a job title given to people who did repetitive 
calculations for navigational tables, planetary positions and other such requirements. 
Tejas: Women with mathematical proficiency were often employed for the job. 
Jyoti: I am sure a lot of calculations were involved in building pyramids and Taj Mahal.
Tejas: Of course mathematics and physics knowledge was applied to weave the designs for the 
beautiful old tapestry that we see in many places.
Moz: Good observations. So they started inventing devices for precise calculations and automation 
of certain tasks. One of the important automation which is the Jaquard loom is important in the 
computer history.
Jyoti: The Jacquard loom invented by Joseph Marie Jacquard 
used punched cards to control a sequence of operations. A 
pattern of the loom’s weave could be changed by changing the  
punched card. 
Moz: Why do you think Jacquard looms are important?
Tejas: The loom weaves the design on the punched card by 
executing the sequence of operations on the card, one line 
after another. This idea is used in modern programming. For 
example, in a Scratch program the computer executes the blocks  
one by one.
Jyoti: In computers we use an input device like keyboard to input 
data. The punched card is like an input to the loom. 
Moz: Yes. You are right. Babbage used the punched card idea to 
store data in his analytical machine.
Tejas: Boolean algebra which is extensively used in computers was also developed in 19
th
 century 
by the mathematician George Boole. 
Moz: Yes. Boolean logic is one of the most important concepts in computers. You will be 
learning about these concepts of programming soon. Note that the 19
th
 century contributions 
of automating  and the development of algorithm are of immense value to the development of 
electronic computers in the 20
th
 century.
Info
Mechanical computation machines- Early 19
th
 century
Automation with punched cards 18
th
-19
th
 century
Trade, travel, and increase in population (which demanded increase in requirements like clothing, 
food etc.), led to automation of machinery in 18
th
-19
th
 century. Developments in logic and need 
for more complicated calculations led to mechanical computation devices which were designed 
and implemented for varied degree of computations. But, accuracy, speed and precision could not  
be ensured due to the wear and tear of the mechanical components.
Babbage- The Analytical Machine
The anlaytical machine was designed but not built. The main parts of the 
machine were called the “store” and “mill”. Punched cards store data, which 
is equivalent to the memory unit in computers. Mill weaves or processes 
the data to give a result, which is equivalent to the central processing unit 
in computers. He used conditional processing of data. Example: If block in 
Scratch. 
ADA	lovelace-	The	first	programmer
ADA lovelace, a	 friend	 of	 Babbage	 wrote	 the	 first	 sequence	 of	 instructions	
for various tasks for the analytical engine. She used programming concept 
of looping for repetitive actions. Example: repeat block in Scratch. She 
used subroutines in her programs.
Hollerith desk 
It consisted of a card reader which sensed the holes in the cards, a gear driven mechanism 
which could count and a large wall of dial indicators to display the results of the count. For 
example: a car speedometer is a dial indicator. This was used for U.S census 1890.
Page 4


Jyoti and Tejas have brought an abacus, 
pictures of old computers, a handmade 
slide rule, a cloth with pretty designs 
and some notes written on sheets of 
paper. Other students are looking on and 
wondering how these articles are related 
to history of computers. 
Simple calculations were done in innovative ways with stones, pebbles and even bones. These 
were called counters. A device with more complicated calculation abilities was the abacus, of 
which we can find many versions.
Abacus – 6
th
 century B. C
Computing Squares and sums by arranging counters
Calculation using fingers
Sieve of Eratosthenes: Finding prime 
numbers in 3
rd
 century B.C
Jyoti: We have gathered history of 
computers right from 3rd century B.C.  
It is very interesting to find what people 
did when there were no computers. 
     Information gathering 
Use of counters to aid calculations: 3
rd 
- 6
th
 century B.C 
The first step for gathering information is to list what you know, what you do not know. Next, gather, consolidate, analyse and organise the 
gathered information. 
1
Aim: In this lesson, you will learn:
- Various devices that have been used for computations in the past.
- Major milestones in development of modern day computers
- Development of Internet, browser and other Internet based applications, 
   games and Linux.
History of Computers: From   
Abacus to Smart phones 8
Moz: We have been using computers for the past 40 years. But the origin of the concepts, algorithms 
and the developments in computations date back to the very early times and cultures.
Tejas: In very early days, when there were no computational devices, people used pebbles, bones 
and the fingers of hands to count and calculate. 
Jyoti: They even used ropes and shapes for some measurements. For example: For assuring a right 
angle, people used 3-4-5 right triangle shape or a rope with 12 evenly spaced knots, which could 
be formed into a 3-4-5 right triangle.
1
Explorations of various continents and trading brought in the requirements of precise calculations 
of sea routes, accounting, planetary positions, and navigational tables- 16
th
 century.
Mechanical devices were also developed to assist in tedious and repetitive calculations like 
generating calendars of a year, taxing and trading. 
The Slide rule was used  for landing man on 
the Moon. This was used by NASA engineers 
in 1960s for the Apollo mission.                                      
Napier bones- Numbers 0 to 9 were marked 
on a set of ivory sticks in such a way that 
the product of any number can be found 
by placing the sticks side by side.                                          
Pascaline built by Pascal for his
father who was a tax collector.
Stepped reckoner by
Leibniz using flutes.
Schikard’s 
calculating
clock with gears
Tejas: Early mathematicians around the world such as al-Khwarizmi, Panini, and Euclid developed 
many algorithms. 
Jyoti: Algorism and algorithm stem from Algoritmi, the Latin form of al-Khwarizmi’s name.
Simple devices to aid human calculations- 16th century
Devices with gears and flutes for calculations- 16th-17th century
Jyoti: The first computers were people. This was a job title given to people who did repetitive 
calculations for navigational tables, planetary positions and other such requirements. 
Tejas: Women with mathematical proficiency were often employed for the job. 
Jyoti: I am sure a lot of calculations were involved in building pyramids and Taj Mahal.
Tejas: Of course mathematics and physics knowledge was applied to weave the designs for the 
beautiful old tapestry that we see in many places.
Moz: Good observations. So they started inventing devices for precise calculations and automation 
of certain tasks. One of the important automation which is the Jaquard loom is important in the 
computer history.
Jyoti: The Jacquard loom invented by Joseph Marie Jacquard 
used punched cards to control a sequence of operations. A 
pattern of the loom’s weave could be changed by changing the  
punched card. 
Moz: Why do you think Jacquard looms are important?
Tejas: The loom weaves the design on the punched card by 
executing the sequence of operations on the card, one line 
after another. This idea is used in modern programming. For 
example, in a Scratch program the computer executes the blocks  
one by one.
Jyoti: In computers we use an input device like keyboard to input 
data. The punched card is like an input to the loom. 
Moz: Yes. You are right. Babbage used the punched card idea to 
store data in his analytical machine.
Tejas: Boolean algebra which is extensively used in computers was also developed in 19
th
 century 
by the mathematician George Boole. 
Moz: Yes. Boolean logic is one of the most important concepts in computers. You will be 
learning about these concepts of programming soon. Note that the 19
th
 century contributions 
of automating  and the development of algorithm are of immense value to the development of 
electronic computers in the 20
th
 century.
Info
Mechanical computation machines- Early 19
th
 century
Automation with punched cards 18
th
-19
th
 century
Trade, travel, and increase in population (which demanded increase in requirements like clothing, 
food etc.), led to automation of machinery in 18
th
-19
th
 century. Developments in logic and need 
for more complicated calculations led to mechanical computation devices which were designed 
and implemented for varied degree of computations. But, accuracy, speed and precision could not  
be ensured due to the wear and tear of the mechanical components.
Babbage- The Analytical Machine
The anlaytical machine was designed but not built. The main parts of the 
machine were called the “store” and “mill”. Punched cards store data, which 
is equivalent to the memory unit in computers. Mill weaves or processes 
the data to give a result, which is equivalent to the central processing unit 
in computers. He used conditional processing of data. Example: If block in 
Scratch. 
ADA	lovelace-	The	first	programmer
ADA lovelace, a	 friend	 of	 Babbage	 wrote	 the	 first	 sequence	 of	 instructions	
for various tasks for the analytical engine. She used programming concept 
of looping for repetitive actions. Example: repeat block in Scratch. She 
used subroutines in her programs.
Hollerith desk 
It consisted of a card reader which sensed the holes in the cards, a gear driven mechanism 
which could count and a large wall of dial indicators to display the results of the count. For 
example: a car speedometer is a dial indicator. This was used for U.S census 1890.
Jyoti: These were used for limited purposes like solving mathematical equations, decoding messages, 
or for tables of firing artillery in world war II.
Moz: Yes. These computers were based on binary representation of data and boolean algebra.
Tejas: Early 20
th
 century saw many analog computers which were mechanical or electrical or 
electromechanical devices. 
Jyoti: In 1945, Von Neumann devised the “Stored program architecture”. This changed the way a  
program was written and altered. 
Moz: Yes. The program and data were stored in memory and instructions were processed one 
after the other. 
Tejas: The input was typed on a terminal which looks like a monitor with keyboard in the front, or 
on cards. Each instruction was typed on one card and the deck of cards was read by a card reader 
and stored in memory. 
Moz: Those who submitted the program had to wait till their program was processed to obtain 
the printed output.
Jyoti: If the programmer had to change the program, they had to type in another card and insert 
it in the deck of cards. 
Analog computers- First general purpose computers- first half of 1900-1940
The war time requirements for artillery firing, communication of strategies using complicated 
codes led to electromechanical computers where magnetic storage and vacuum tubes were first 
used. Babbage’s punched card was used to input data.
1936 : Alan Turing regarded to be the father of modern Computer Science provided a 
formalisation for the concept of algorithm and computations.
1941 : Konrad Zuse	 inventor	 of	 the	 program-contro lled	 computer,	 built	 the	 first	 working	
computer. This computer was based on magnetic storage.
1942 : Atanasoff-Berry computer which used vacuum tube, binary numbers, was non 
programmable. 
1943 : Colossus a secret British computer with limited programmability built using vaccum 
tubes,	 was	 built	 to	 break	 the	 German	 wartime	 codes.	 It	 was	 the	 first	 computer	 to	 read	 and	
decipher the codes using cryptography.
1944 : Harvard Mark I an electromechanical computer built out of switches, relays, rotating 
shafts, and clutches had limited programmability. It used punched paper tape instead of the 
punched cards. It worked for almost 15 years. Grace Hopper was the primary programmer. 
She	 invented	 the	 first	 high	 level	 language	 called	Flow-Matic which later developed into 
COBOL.	 She	 also	 constructed	 the	 first	 compiler.	 She	 found	 the	 first	 computer	 “bug”:	 a	 dead	
moth that  got into the Mark I and whose wings were blocking the reading of the holes in 
the paper tape. The word “bug” had been used to describe a defect since at least 1889 
but Hopper is credited with coining the word “debugging” to describe the work to eliminate 
program faults. 
Info
Mechanical computation machines - 20
th
 century
Digital computers- 1940 to 1970
Census, elections, research in various fields and many such advances in different fields required 
increased speed, precision and immediate results. In the mid 1940s, stored program digital 
computer architecture was designed with CPU and memory to hold instructions and data.
Page 5


Jyoti and Tejas have brought an abacus, 
pictures of old computers, a handmade 
slide rule, a cloth with pretty designs 
and some notes written on sheets of 
paper. Other students are looking on and 
wondering how these articles are related 
to history of computers. 
Simple calculations were done in innovative ways with stones, pebbles and even bones. These 
were called counters. A device with more complicated calculation abilities was the abacus, of 
which we can find many versions.
Abacus – 6
th
 century B. C
Computing Squares and sums by arranging counters
Calculation using fingers
Sieve of Eratosthenes: Finding prime 
numbers in 3
rd
 century B.C
Jyoti: We have gathered history of 
computers right from 3rd century B.C.  
It is very interesting to find what people 
did when there were no computers. 
     Information gathering 
Use of counters to aid calculations: 3
rd 
- 6
th
 century B.C 
The first step for gathering information is to list what you know, what you do not know. Next, gather, consolidate, analyse and organise the 
gathered information. 
1
Aim: In this lesson, you will learn:
- Various devices that have been used for computations in the past.
- Major milestones in development of modern day computers
- Development of Internet, browser and other Internet based applications, 
   games and Linux.
History of Computers: From   
Abacus to Smart phones 8
Moz: We have been using computers for the past 40 years. But the origin of the concepts, algorithms 
and the developments in computations date back to the very early times and cultures.
Tejas: In very early days, when there were no computational devices, people used pebbles, bones 
and the fingers of hands to count and calculate. 
Jyoti: They even used ropes and shapes for some measurements. For example: For assuring a right 
angle, people used 3-4-5 right triangle shape or a rope with 12 evenly spaced knots, which could 
be formed into a 3-4-5 right triangle.
1
Explorations of various continents and trading brought in the requirements of precise calculations 
of sea routes, accounting, planetary positions, and navigational tables- 16
th
 century.
Mechanical devices were also developed to assist in tedious and repetitive calculations like 
generating calendars of a year, taxing and trading. 
The Slide rule was used  for landing man on 
the Moon. This was used by NASA engineers 
in 1960s for the Apollo mission.                                      
Napier bones- Numbers 0 to 9 were marked 
on a set of ivory sticks in such a way that 
the product of any number can be found 
by placing the sticks side by side.                                          
Pascaline built by Pascal for his
father who was a tax collector.
Stepped reckoner by
Leibniz using flutes.
Schikard’s 
calculating
clock with gears
Tejas: Early mathematicians around the world such as al-Khwarizmi, Panini, and Euclid developed 
many algorithms. 
Jyoti: Algorism and algorithm stem from Algoritmi, the Latin form of al-Khwarizmi’s name.
Simple devices to aid human calculations- 16th century
Devices with gears and flutes for calculations- 16th-17th century
Jyoti: The first computers were people. This was a job title given to people who did repetitive 
calculations for navigational tables, planetary positions and other such requirements. 
Tejas: Women with mathematical proficiency were often employed for the job. 
Jyoti: I am sure a lot of calculations were involved in building pyramids and Taj Mahal.
Tejas: Of course mathematics and physics knowledge was applied to weave the designs for the 
beautiful old tapestry that we see in many places.
Moz: Good observations. So they started inventing devices for precise calculations and automation 
of certain tasks. One of the important automation which is the Jaquard loom is important in the 
computer history.
Jyoti: The Jacquard loom invented by Joseph Marie Jacquard 
used punched cards to control a sequence of operations. A 
pattern of the loom’s weave could be changed by changing the  
punched card. 
Moz: Why do you think Jacquard looms are important?
Tejas: The loom weaves the design on the punched card by 
executing the sequence of operations on the card, one line 
after another. This idea is used in modern programming. For 
example, in a Scratch program the computer executes the blocks  
one by one.
Jyoti: In computers we use an input device like keyboard to input 
data. The punched card is like an input to the loom. 
Moz: Yes. You are right. Babbage used the punched card idea to 
store data in his analytical machine.
Tejas: Boolean algebra which is extensively used in computers was also developed in 19
th
 century 
by the mathematician George Boole. 
Moz: Yes. Boolean logic is one of the most important concepts in computers. You will be 
learning about these concepts of programming soon. Note that the 19
th
 century contributions 
of automating  and the development of algorithm are of immense value to the development of 
electronic computers in the 20
th
 century.
Info
Mechanical computation machines- Early 19
th
 century
Automation with punched cards 18
th
-19
th
 century
Trade, travel, and increase in population (which demanded increase in requirements like clothing, 
food etc.), led to automation of machinery in 18
th
-19
th
 century. Developments in logic and need 
for more complicated calculations led to mechanical computation devices which were designed 
and implemented for varied degree of computations. But, accuracy, speed and precision could not  
be ensured due to the wear and tear of the mechanical components.
Babbage- The Analytical Machine
The anlaytical machine was designed but not built. The main parts of the 
machine were called the “store” and “mill”. Punched cards store data, which 
is equivalent to the memory unit in computers. Mill weaves or processes 
the data to give a result, which is equivalent to the central processing unit 
in computers. He used conditional processing of data. Example: If block in 
Scratch. 
ADA	lovelace-	The	first	programmer
ADA lovelace, a	 friend	 of	 Babbage	 wrote	 the	 first	 sequence	 of	 instructions	
for various tasks for the analytical engine. She used programming concept 
of looping for repetitive actions. Example: repeat block in Scratch. She 
used subroutines in her programs.
Hollerith desk 
It consisted of a card reader which sensed the holes in the cards, a gear driven mechanism 
which could count and a large wall of dial indicators to display the results of the count. For 
example: a car speedometer is a dial indicator. This was used for U.S census 1890.
Jyoti: These were used for limited purposes like solving mathematical equations, decoding messages, 
or for tables of firing artillery in world war II.
Moz: Yes. These computers were based on binary representation of data and boolean algebra.
Tejas: Early 20
th
 century saw many analog computers which were mechanical or electrical or 
electromechanical devices. 
Jyoti: In 1945, Von Neumann devised the “Stored program architecture”. This changed the way a  
program was written and altered. 
Moz: Yes. The program and data were stored in memory and instructions were processed one 
after the other. 
Tejas: The input was typed on a terminal which looks like a monitor with keyboard in the front, or 
on cards. Each instruction was typed on one card and the deck of cards was read by a card reader 
and stored in memory. 
Moz: Those who submitted the program had to wait till their program was processed to obtain 
the printed output.
Jyoti: If the programmer had to change the program, they had to type in another card and insert 
it in the deck of cards. 
Analog computers- First general purpose computers- first half of 1900-1940
The war time requirements for artillery firing, communication of strategies using complicated 
codes led to electromechanical computers where magnetic storage and vacuum tubes were first 
used. Babbage’s punched card was used to input data.
1936 : Alan Turing regarded to be the father of modern Computer Science provided a 
formalisation for the concept of algorithm and computations.
1941 : Konrad Zuse	 inventor	 of	 the	 program-contro lled	 computer,	 built	 the	 first	 working	
computer. This computer was based on magnetic storage.
1942 : Atanasoff-Berry computer which used vacuum tube, binary numbers, was non 
programmable. 
1943 : Colossus a secret British computer with limited programmability built using vaccum 
tubes,	 was	 built	 to	 break	 the	 German	 wartime	 codes.	 It	 was	 the	 first	 computer	 to	 read	 and	
decipher the codes using cryptography.
1944 : Harvard Mark I an electromechanical computer built out of switches, relays, rotating 
shafts, and clutches had limited programmability. It used punched paper tape instead of the 
punched cards. It worked for almost 15 years. Grace Hopper was the primary programmer. 
She	 invented	 the	 first	 high	 level	 language	 called	Flow-Matic which later developed into 
COBOL.	 She	 also	 constructed	 the	 first	 compiler.	 She	 found	 the	 first	 computer	 “bug”:	 a	 dead	
moth that  got into the Mark I and whose wings were blocking the reading of the holes in 
the paper tape. The word “bug” had been used to describe a defect since at least 1889 
but Hopper is credited with coining the word “debugging” to describe the work to eliminate 
program faults. 
Info
Mechanical computation machines - 20
th
 century
Digital computers- 1940 to 1970
Census, elections, research in various fields and many such advances in different fields required 
increased speed, precision and immediate results. In the mid 1940s, stored program digital 
computer architecture was designed with CPU and memory to hold instructions and data.
Jyoti: Microprocessor revolution brought in the explosion of usage of computers in every field.
Tejas: The size of computers started decreasing and the speed started increasing.
Jyoti: The storage space also started increasing.
Tejas: Most importantly the reliability of computers increased and the cost started decreasing.
Moz: Yes. Invention of microprocessors revolutionised the computer development and due to the 
reduction of cost, by 1990, owning a personal computer became common.
Computers with Microprocessors- 1970 onwards 
Use of microprocessors in computers increased reliability, precision and reduced size and cost.
This led to uses of computers in offices, colleges, personal use and exploration of computer usage 
in every field. 
First generation computers
These computers made from 1945-55 were named ENIAC, EDVAC and UNIVAC. The 
processor (or CPU) in these computers were made of vaccum tubes. They were  the size 
of an entire room, over 5 meters high and very costly to maintain.
Second generation computers 
These computers developed after 1955 and had transistors in the place of vaccum tubes in 
the processor. Transistors were more reliable, much cheaper and smaller. This generation 
computers had more computing power, were smaller in size, easier to maintain and were 
more affordable than the previous generation.
Third generation computers 
These computers developed in the 1960’s, used integrated circuits. The trasistors were 
miniaturised and kept on silicon chips called semiconductors, which drastically increased 
the	speed	and	efficiency	of	computers.
Fourth generation computers 
These  were developed in the 1970s and used microprocessors or chips. The 
microprocessors were smaller than a postage stamp and had tremendous computing 
capabilities.
Fifth generation computers 
These were developed in 1980s and used the concept of Artificial	 Intelligence. The 
different	 types	 of	 fifth	 generation	 computers	 are	 Desktop, notebook or laptop, palmtop, 
server, Mainframe and Super Computer. 
Desktop computers are based on ICs. •	
Notebook or laptop computer is same as desktop but can be carried around. •	
Palmtop is a miniature version of notebook with limited capabilities. •	
Server is a powerful version of desktop capable of catering to various applications in •	
a network environment.
Mainframe is a powerful version of server and is capable of handling huge applications •	
and data processing.
Super	 computer	 has	 multiprocessors	 to	 perform	 typical	 scientific	 applications	 that	 need	 •	
trillions of information per second while processing. 
Info Info
Computation machines- Second half of 19
th
 century
Computation machines- After 1970s
These computers were built using vacuum tubes, transistors and integrated circuits, and are classified 
into the first three generations of computers respectively. The classification of generations is  
based on technology, speed, storage, reliability and cost.