Introduction to computer and programming Lec 01 Part 02 (Brief History of Computer)

Main ideas / concepts covered

Early mechanical computing (Pascaline)

• Introduces the Pascaline, an early mechanical calculator invented by French mathematician and philosopher Blaise Pascal in 1642.
• Describes how addition and subtraction work using:
  • Input dials: each dial uses a stylus to rotate and enter digits
  • Output windows: display results
  • A drum with digits 0–9
  • Subtraction via nine’s complement: subtraction is performed by showing nine’s complement values

Method for addition using the Pascaline

• Digits are entered by position (tens, ones, etc.).
• Procedure (example: 38 + 42):
  • Enter the first addend:
    • Enter 3 (tens place) then 8 (ones place)
  • Enter the second addend:
    • Add 4 to the tens place and 2 to the ones place
  • Carry handling:
    • If a digit sum reaches 10:
      • Ones place becomes 0
      • 1 carries into the next higher place
• Example explicitly shown:
  • 38 + 42 = 80 (demonstrated via dial operations)

Clearing / resetting after an operation (Pascaline)

• To start a new calculation, the stored value must be cleared:
  • Set all input dials so they show 9
  • Then add 1 to the lowest-order digit
  • The resulting carry effectively resets the output windows back to 0

Method for subtraction using nine’s complement

• Subtraction uses nine’s complement:
  • A horizontal slat is moved to reveal the top output row containing nine’s complement values
• Procedure (example: 80 − 50):
  • Reveal the nine’s complement output row
  • Enter the minuend (80) using the nine’s complement method
  • Enter the subtrahend (50) in the normal way
    • Notes indicate the ones place may effectively be 0, so fewer digits may need entry
• Result shown:
  • 80 − 50 = 30

Demonstration of another mechanical calculator (pinwheel)

• A presenter demonstrates a “pinwheel mechanical calculator” purchased online.
• Claims and context:
  • “Last produced in 1958”
  • Presented as about 56 years old at the time of filming
• Controls and features:
  • Input counter/dials for entering numbers
  • Clear lever
  • Output / turn counter
  • A rocker/release mechanism to align digits with the correct place value
  • A direction lever:
    • Clockwise → addition and multiplication
    • Counterclockwise → subtraction and division
• Example operations shown:
  • Multiplication via repeated addition
    • 2 × 1 = 2
    • 2 × 2 = 4
    • Notes that the turn counter can be ignored for interpreting addition/multiplication
  • Addition example
    • Mentions 4 + 25 = 29 (not shown fully step-by-step in the excerpt)
  • Subtraction example
    • 25 − 3 = 22
• Division procedure (repeated subtraction; no negative handling):
  • Division is implemented as repeated subtraction.
  • The presenter clears/locks the turn counter, treating it as the division output/quotient.
  • When subtraction would go negative:
    • The machine signals (bell sound) and an invalid state appears
    • The operator adjusts (shift-and-try-again)
  • Outputs:
    • Quotient on the turn counter (multi-digit)
    • Remainder on another counter
  • Example stated:
    • Dividing 3120 64 by 13 (subtitle transcription is messy)
  • Final shown output:
    • 243 with remainder 5

Jacquard loom and punch card computing as ancestry of computers

• Introduces ~200-year-old Jacquard technology associated with Joseph-Marie Jacquard.
• Punch card “programming” analogy:
  • A fabric design is translated to graph paper
  • The craftsperson transfers the design into punch cards
  • Each punch card row corresponds to one row of the pattern
  • Cards are assembled into a sequence (“chain of punch cards”)
  • The card chain is attached to a loom:
    • Holes select threads, allowing hooks to pass
  • The loom weaves fabric by moving threads over and under using the shuttle
• Workshop/studio context:
  • Mentions “for spina studio,” preserving authenticity in Nepal
  • References “probably the last generation of Jacquard craftsmen in Nepal”
  • Intends to keep the Zakar/Jacquard tradition alive (spelling varies in subtitles: “zakardom,” “zakar,” “jacquard”)

---

Instructional / methodology bullet points (as presented)

Pascaline: Addition procedure (including carry handling)

• Enter each digit using the stylus:
  • Each dial has 10 sections (0–9)
  • Insert the stylus into the correct spoke section for the desired digit
  • Rotate clockwise until the spoke reaches the fixed stop / metal indicator
• For 38 + 42 (example):
  • Enter 3 in the tens place and 8 in the ones place
  • Add 4 to the tens place and 2 to the ones place
  • If a digit sum reaches 10:
    • Ones digit becomes 0
    • Carry 1 adds into the next higher place
• Output appears in the output windows after the dial movements

Pascaline: Clearing the stored value

• Set all input dials to 9
• Then add 1 to the lowest-order digit
• This carry operation resets output windows back to 0

Pascaline: Subtraction procedure using nine’s complement

• Move the horizontal slat to reveal the nine’s complement output row
• Enter the minuend using nine’s complement values
• Enter the subtrahend in the normal manner for the relevant digit places
  • Subtitle notes that the ones place may not require entry if it is effectively zero for that step
• The resulting output windows show the subtraction answer

Pinwheel mechanical calculator: Lever direction for operations

• Pull out the lever
• Rotate the lever:
  • Clockwise → addition and multiplication
  • Counterclockwise → subtraction and division
• Reset/clear mechanisms:
  • Reset both input and turn counters as needed
  • Align digits by moving the display to the correct starting position (to match place value)

Pinwheel mechanical calculator: Division as repeated subtraction

• Before division:
  • Clear/reset the turn counter (since it represents the quotient/output)
  • A feature/switch may prevent erasing the output during division
• Division steps (as described):
  • Align the divisor subtraction starting digit properly
  • Repeatedly subtract the divisor from the current value:
    • If subtraction would go negative (machine cannot represent it):
      • It “dings/bells” and shows an invalid state
      • Shift and try again
  • Continue until the machine signals termination and produces the final quotient/range
• Reading outputs:
  • Quotient from the turn counter (red numbers after rollback in the demo)
  • Remainder from a separate counter

Jacquard loom / punch card “programming” methodology

• Translate pattern design to graph paper
• Convert the graph design into punch cards:
  • Each punch card corresponds to one row of the pattern
• Assemble punch cards into a sequence/chain
• Attach the card chain to the loom’s machine
• Holes in the cards determine which threads are lifted/selected
• Weave fabric using a shuttle and thread path (over/under)

---

Speakers / sources featured (as identifiable from subtitles)

• Blaise Pascal — credited as the inventor of the Pascaline (1642)
• Joseph-Marie Jacquard — credited with Jacquard technology and the punch card technique
• A video presenter/demonstrator (unnamed) — demonstrates a pinwheel mechanical calculator, including operations (addition, multiplication, subtraction, division) and reading outputs