MECHANICAL COUNTING AND CALCULATING DEVICES
Subject :
Computer Studies (ICT)
Term :
First Term / 1st Term
Week:
Week 2
Class :
JSS 1 / Basic 7
Previous lesson :
The pupils have previous knowledge of
HISTORICAL DEVELOPMENT OF COMPUTERS: EARLY COUNTING DEVICES
in their previous classes
Topic :
MECHANICAL COUNTING AND CALCULATING DEVICES
Behavioural objectives:
At the end of the lesson, the pupils should be able to
- define mechanical counting devices
- state mechanical counting devices
- Give examples of early mechanical devices
- Mention the various stages of mechanical computer development
Instructional Materials:
- Wall charts
- Pictures of different types of houses
- Related Online Video
- Flash Cards
Methods of Teaching:
- Class Discussion
- Group Discussion
- Asking Questions
- Explanation
- Role Modelling
- Role Delegation
Reference Materials:
- Scheme of Work
- Online Information
- Textbooks
- Workbooks
- 9 Year Basic Education Curriculum
- Workbooks
Content:
Mechanical Counting and Calculating Devices
As a result of the disadvantages of the early counting devices, more advanced mechanical counting and calculating devices were invented. Some of these devices are;
- Abacus (Chinese)
- Napier’s Bone (John Napier)
- Slide Rule (William Oughtred)
THE ABACUS
The Abacus is made up of beads threaded on iron rods. The iron rods are fixed to a rectangular wooden frame. It is used for addition and subtraction only. It could not carry out complex mathematics. The Abacus was early used for arithmetic tasks, it was developed in China about 5000 years ago. It was successful that its use spread from china to many other countries.
NAPIER’S BONE
After the Abacus, the next significant development was the Napier’s Bone made by John Napier in the year 1617. John Napier was a mathematician, physicist, and astronomer from Scotland. His most important achievement was the discovery of logarithms. He also made the use of the decimal point in arithmetic and mathematics common. Napier’s bone is a manually-operated calculating device for calculation of products and quotients of numbers.
Using the multiplication tables in the rods, multiplication can be reduced to addition and division to subtractions. More advanced use of the rods can even extract square roots. Napier’s bone is not the same as logarithms, with which Napier’s name is also associated. The complete device usually includes a base board with a rim; the user places Napier’s rods inside the rim to carry out multiplication or division. The board’s left edge is divided into 9 squares, holding the numbers 1 to 9. The Napier’s rod is made up of of strips of wood, metal or heavy cardboard. Napier’s bone is three-dimensional, square in cross section, with four different rods embedded on each one.
SLIDE RULE
The slide Rule which is also called the slip-stick in the United States of America was invented around 1620-1630 shortly after John Napier’s publication of the concept of logarithms. It is a mechanical analogue computer. The slide rule is used mostly for multiplication, division, and also for functions as roots, algorithms and trigonometry, but is not normally used for addition or subtraction.
Slide rules come in different range of styles and generally appear in a straight or circular form with a standardized set of markings (scales) essential to performing mathematical operations.
The use of slide rule continued to grow through the 1950s and 1960s even as digital computing devices were being gradually introduced.
Presentation
The topic is presented step by step
Step 1:
The class teacher revises the previous topics
Step 2.
He introduces the new topic
Step 3:
The class teacher allows the pupils to give their own examples and he corrects them when the needs arise
Conclusion
The class teacher wraps up or concludes the lesson by giving out a short note to summarize the topic that he or she has just taught.
The class teacher also goes round to make sure that the notes are well copied or well written by the pupils.
He or she does the necessary corrections when and where the needs arise.
EVALUATION
- Mention two examples of mechanical counting/calculating devices
- Who invented the Speeding clock?
- To perform Multiplication on the Speeding clock, ………… was added to it
- The slide rule was invented by …………..
- Another name for Slide Rule is ……………
