What is Computation?

Lecture Notes

I have prior knowledge on computation and programming, so I will recall instead of noting something new.

• computation
• algorithm
• Binary Search

• Computation is the process of counting something. It comes from the word “compute” which means “to count”.

  Computers do computation. That’s why they are called computer, they do computation.

  Computers are not human. Well, at the time when I write this you may have heard of AI which seems to give “life” to computer but that’s nothing compared to life. Computer only memorize and do things as we told them. Explicitly. If we ask the computer to “calculate the area of this square using this formula”, then the computer will do the job.

  You might be thinking that it is basic. But wait, that’s not all.

  What if we give our computer the formula of a “triangle area” instead of a “square area”? Guess what, computers don’t understand it and will use triangle area instead of square formula. Why this happens? It’s because computer will only do the task they are told to. If we told them to calculate the area of a square but we give them the formula of a triangle area, then the computer will use the triangle area formula.

  Explicit is the key.

• As said in the previous tab section, computers only know how to memorize and do things (explicitly). For computers to memorize, we simply declare it to the computer. It’s something similar to, “this is a pen”, in a way that “x is 9”. It’s [object] = [value]. That is how we declare a variable for the computers to memorize. And they are good at it.

  Algorithm, on the other hand, is equivalent to a recipe, a procedure text, or “how to do things orderly”. Let’s say we want to toast a bread.

  1. Prepare two slices of bread.
  2. Plug the toaster into a wall socket.
  3. Put the bread slices into the toaster.
  4. Pull down the lever on the toaster that makes the bread comes down.
  5. Wait for the timer to end.
  6. As soon as the toaster finished toasting the bread, it will pull out the bread.
  7. Take out the bread. 8 Serve the bread on a plate.

  Above is an example of algorithm for humans. For computers, it’s quite the same but they need extra details and meticulous instructions. For example:

  1. Prepare two slices of bread

  is equivalent to:

  1. Pick up the bread bag.
  2. Move to nearby desk.
  3. Put bread bag on the desk.
  4. Open the bread bag.
  5. Take two slices of bread out of the bag.
  6. Put the bread on a temporary plate.

• I have seen how binary or bisection search on YouTube. Guess what? I watched searching algorithm at 2 AM when I was should have slept.

  In short, binary search is a searching algorithm to find the best value from a simple true/false condition. For example: a number guessing game with binary search.

  Take a number between 0 and 100, the computer will guess it.

  The way the computer guess the number is by asking the whether the value is greater than or less than.

  Say you think of 45. The computer will take a random number and ask you back with a True or False question.

  Computer: "Is your number lower than 50?"
  You: "Yes"
  Computer: "Is your number lower than 25?"
  You: "No"
  Computer: "Is your number lower than 37?"
  You: "No"
  Computer: "Is your number lower than 43?"
  You: "No"
  Computer: "Is your number lower than 46?"
  You: "Yes"
  Computer: "Is your number lower than 44?"
  You: "No"
  Computer: "Your number is 45."
  

Problem Sets

There are 6 problem sets in this topic. I intentionally made all problem sets hidden under an expandable details.

import math

x = float(input("Input a value for X: "))
y = float(input("Input a value for Y: "))
exponent = x ** y
log2ofx = math.log(x, 2)

print(f"\n")
print(f"{x} raised to the power of {y} is {exponent}")
print(f"The log base 2 of {x} is {log2ofx}")

Projects

I got some inspirations while watching some videos about “DIY Jet Engine” on YouTube.

• Project 1

• Scales with different starting value

  Idea: Sometimes you want to measure liquid or granular solid objects (like salt), but you need a container. This container has weight, but we only interested in the weight of the stuff and not with the container.

  Goal: Write a program that measures the weight of something while disregarding the weight of the container used to contain the “something”.

  Pseudocode:

  1. User input weight in kg (true_weight).
  2. Check if true_weight is either int or float.
  3. If true_weight is neither int or float, return error message and ask user to input again.
  4. If true_weight is either int or float, ask user whether they use container or not (has_extra) with default answer of “N”.
  5. If user input has_extra is NOT in list of accepted values (“y”, “Y”, “n”, “N”, “”), return error message and ask user to input again.
  6. If user input has_extra is IN list of accepted values (“y”, “Y”, “n”, “N”, “”), check whether has_extra again.
  7. If has_extra is either “y” or “Y”; ask user to input weight for the container (extra_weight)
  8. If has_extra is either “n”, “N”, or “”; return true_weight
  9. Check if extra_weight is either int or float.
  10. If extra_weight neither int or float, return error message and ask user to input again.
  11. If extra_weight either int or float, return print(f"Weight: {true_weight - extra_weight} kg)

  Code:

  # Greetings
  greetings_msg = "Welcome to Virtual Scales"
  ver = "0.2"
  print(greetings_msg)
  print(f"version {ver}")
  
  # Base variables
  valid_responses = ["y", "Y", "n", "N", ""]
  
  # Input
  true_weight = input("Enter weight in kg: ")
  
  # Input validation
  while true_weight.isdigit() != True:
      print("Your weight is NOT a number")
      true_weight = input("Enter weight in kg: ")
  
  # Input
  has_container = input("Do you use container? [y/N] ")
  
  while has_container not in valid_responses:
      print("Error: Invalid response")
      has_container = input("Do you use container? [y/N] ")
  
  if has_container in valid_responses[3:6]:
      print(f"Weight: {float(true_weight)} kg")
  else:
      extra_weight = input("Enter container weight in kg: ")
      
      while extra_weight.isdigit() != True:
          print("Your container weight value is NOT a number")
          extra_weight = input("Enter container weight in kg: ")
      
      new_weight = float(true_weight) - float(extra_weight)
      print(f"Weight: {new_weight} kg")