Algorithms - Pseudocode Convention

Note that this conventions are not complete rules for writing algorithms. These are the widely accepted conventions for uniformity and clarity among global audience.

Comment starts with //.
Statement ends with ;
For block statement, the statement must be enclosed within { .. }
Identifier rules:
- An identifier can only start with letter (A-Z, a-z) or underscore( _ ) symbol.
- An identifier can contain alphabet, digits(0-9), and underscore only.
- The identifier must not contain white spaces.
- A keyword can not use as an identifier.
- You can not use punctuation characters (@, #, $, %, &) as identifers.
- So identifier name should be unique.
Assignment Operator ( $:=$ )
It’s same as Walrus operator in Python.
```
int b;
int a := 10;
b := 20;
```
``
Boolean values (true & false)
Boolean operators ( and / &&, or / ||, not / ! )

Array

int a[10];  // for 1D array in Pseudocode and most of others.
int a[10][10];  // In C / C++ and most of others.
int a[10,10];  // for 2D in Pseudocode.

It’s index starts from 0. If explicitly mentioned, the array index starts from the mentioned number, else starts from 0.

// A is an array index starts from 1.
A[1] is the first element here.

// B is an array.
B[0] is the first element here.

Loops

for, while, repeat until repeat until is the substitution for do...while.

i. for loop :

for i := 1 to 10 step 1 do {
	// some work here.
}

ii. while loop :

while < condition > do {
	// some work here.
}

ii. repeat ... while loop :

repeat {
	// some work here.
}  while < condition >

Conditionals

if, if ... else, if ... elseif ... else

if <condition> then { ... }
// for compound statement.

if <condition> then statement.
// for single statement.

if <condition> then { ... } else { ... }
// for else statement.

if <condition> then { ... } elseif <condition> then { ... }
// for elseif stataement.

case {
	: <condition> : <statement>
	// other condition here.
	:else : <statemtent> // for default case.
}

Input and Output

read n; // read variable from user.
write n; // stdout n.

Procedure definition

Algorithm FirstNNaturalNumbers (par1, par2) {

}

Algorithm is always titlecase.

Example

An algorithm to find the maximum number among the list of numbers.

Algorithm MaxNumber (arr, n) {
	// arr is an array of size n starting from index 0.
	// result is a variable to store the max element.

	result := arr[0];

	for i := 1 to n-1 step 1 do {
		if (arr[i] > result) then result := arr[i];
	}

	write result;
}

Example#

Example