Algorism is the technique of performing basic arithmetic by writing numbers in place value form and applying a set of memorized rules and facts to the digits. One who practices algorism is known as an algorist. [1]

Algorism is derived from the name of a Persian mathematician, Al-Khwārizmī (c. 780–850), who wrote a treatise on arithmetic with Hindu-Arabic numerals in the 9th century. His name was Latinized as Algoritmi, and his work was translated into Latin in the 12th century under the title Algoritmi de numero Indorum (Algoritmi on the numbers of the Indians). [2]

Algorism was the dominant method of arithmetic in Europe from the 13th to the 16th centuries, and it largely superseded earlier calculation systems that used a different set of symbols for each numerical magnitude, such as Roman numerals, and in some cases required a device such as an abacus. [3]

Algorism introduced the concept of the decimal fractions as an extension of the notation, which in turn led to the notion of the decimal point. This system was popularized in Europe by Leonardo of Pisa, also known as Fibonacci. [4]

The word algorithm also derives from algorism, but it has a more general meaning of any set of rules specifying a computational procedure. Occasionally algorism is also used in this generalized meaning, especially in older texts. [5]

1. Algorism – Wikipedia. https://en.wikipedia.org/wiki/Algorism
2. Algorithm Definition & Meaning – Merriam-Webster. https://www.merriam-webster.com/dictionary/algorithm
3. Algorism vs. Algorithm – What’s the difference? | Ask Difference. https://www.askdifference.com/algorism-vs-algorithm/
4. Solar core – Wikipedia. https://en.wikipedia.org/wiki/Solar_core
5. Algorithm – definition of algorithm by The Free Dictionary. https://www.thefreedictionary.com/algorithm

To illustrate how algorism works, let’s look at some examples of algorithms that use the technique of writing numbers in place value form and applying rules to the digits. We will use pseudocode to describe the steps of the algorithms.

This algorithm takes two numbers as input from the user and displays their sum as output.

Algorithm: Add two numbers
Step 1: Start
Step 2: Declare variables num1, num2 and sum
Step 3: Read values num1 and num2 from the user
Step 4: Add num1 and num2 and assign the result to sum
        sum = num1 + num2
Step 5: Display sum
Step 6: Stop

This algorithm takes three numbers as input from the user and displays the largest number among them as output.

Algorithm: Find the largest number
Step 1: Start
Step 2: Declare variables num1, num2, num3 and max
Step 3: Read values num1, num2 and num3 from the user
Step 4: Assign num1 to max
        max = num1
Step 5: If num2 is greater than max, then assign num2 to max
        if (num2 > max) then
            max = num2
Step 6: If num3 is greater than max, then assign num3 to max
        if (num3 > max) then
            max = num3
Step 7: Display max
Step 8: Stop