# What is an Algorithm?

n computer programming terms, an algorithm is a set of well-defined instructions to solve a particular problem. It takes a set of input and produces a desired output. For example,

An algorithm to add two numbers:

``````Take two number inputs

Add numbers using the + operator

Display the result
``````

Qualities of Good Algorithms

``````Input and output should be defined precisely.
Each step in the algorithm should be clear and unambiguous.
Algorithms should be most effective among many different ways to solve a problem.
An algorithm shouldn't include computer code. Instead, the algorithm should be written in such a way that it can be used in different programming languages.
``````

Algorithm 1: Add two numbers entered by the user

Step 1: Start
Step 2: Declare variables num1, num2 and sum.
Step 3: Read values num1 and num2.
Step 4: Add num1 and num2 and assign the result to sum.
sum←num1+num2
Step 5: Display sum
Step 6: Stop

Algorithm 2: Find the largest number among three numbers

Step 1: Start
Step 2: Declare variables a,b and c.
Step 3: Read variables a,b and c.
Step 4: If a > b
If a > c
Display a is the largest number.
Else
Display c is the largest number.
Else
If b > c
Display b is the largest number.
Else
Display c is the greatest number.
Step 5: Stop

Algorithm 3: Find Root of the quadratic equatin ax2 + bx + c = 0

Step 1: Start
Step 2: Declare variables a, b, c, D, x1, x2, rp and ip;
Step 3: Calculate discriminant
D ← b2-4ac
Step 4: If D ≥ 0
r1 ← (-b+√D)/2a
r2 ← (-b-√D)/2a
Display r1 and r2 as roots.
Else
Calculate real part and imaginary part
rp ← -b/2a
ip ← √(-D)/2a
Display rp+j(ip) and rp-j(ip) as roots
Step 5: Stop

Algorithm 4: Find the factorial of a number

Step 1: Start
Step 2: Declare variables n, factorial and i.
Step 3: Initialize variables
factorial ← 1
i ← 1
Step 4: Read value of n
Step 5: Repeat the steps until i = n
5.1: factorial ← factorial*i
5.2: i ← i+1
Step 6: Display factorial
Step 7: Stop

Algorithm 5: Check whether a number is prime or not

Step 1: Start
Step 2: Declare variables n, i, flag.
Step 3: Initialize variables
flag ← 1
i ← 2
Step 4: Read n from the user.
Step 5: Repeat the steps until i=(n/2)
5.1 If remainder of n÷i equals 0
flag ← 0
Go to step 6
5.2 i ← i+1
Step 6: If flag = 0
Display n is not prime
else
Display n is prime
Step 7: Stop

Algorithm 6: Find the Fibonacci series till the term less than 1000

Step 1: Start
Step 2: Declare variables first_term,second_term and temp.
Step 3: Initialize variables first_term ← 0 second_term ← 1
Step 4: Display first_term and second_term
Step 5: Repeat the steps until second_term ≤ 1000
5.1: temp ← second_term
5.2: second_term ← second_term + first_term
5.3: first_term ← temp
5.4: Display second_term
Step 6: Stop