Common Pseudocode

General notes

This "language" works like JavaScript, where each new line is treated as a statement with an implicit "semicolon" (which we don't have in Pseudocode) at the end of each line.

Indentation is done Python style, but without the need for the : at the end of the parent "statement".

Code format

Comments

Single line comment:

// This is a single-line comment
x = 5  // This is an inline comment

Multi-line comment:

/*
    This is a multi-line comment
    that spans multiple lines
*/
x = 10

Input and Output

Read in a user input to the variable userInput: input userInput

Read in a user input to the variable outputInput following an output of Please enter an input:

output "Please enter an output: "
input outputInput

"Print" the value in the variable outputToUser to the "standard output" (or the equivalent place): output outputToUser

Data Types

Explicitly declare variable types (optional in most pseudocode):

number age = 25
string name = "John"
number price = 19.99
boolean isActive = true
array numbers = [1, 2, 3]

Type conversion:

stringValue = "123"
numValue = convert stringValue to number  // or number(stringValue)
stringFromNum = convert age to string  // or string(age)

Assignment

Declare a variable without an initial value: define variableName

Assign the variable newNumber to the value of 7: newNumber = 7

Assign the variable currentNumber to newNumber: currentNumber = newNumber

Example with define:

define counter
define userName
define isValid

counter = 0
userName = "John"
isValid = true

Constants

Define a constant (value cannot be changed):

constant PI = 3.14159
constant MAX_USERS = 100

Strings

"This is a string", 'This is also a string', `This yet again, is a string`

`
This is a multiline string
`

"""
This is also a multiline string
"""

Booleans

true = True = TRUE, false = False = FALSE fAlse, fALSE, trUe, and tRuE are not booleans.

Operators

Addition: 1 + 1 Subtraction: 1 - 1 Multiplication: 1 * 1 Division: 1 / 1

To the power of (exponentiation): 1 ^ 1 or 1 ** 1 or 1 to the power of 1 Remainder (modulus): 1 % 1 or 1 modulus 1 or remainder after 1 / 1

Advanced operator usage: num = num + 1 = num++ num = num * age = num*=age num = num ^ 1000 = num^=1000

num = 8
ans = num/3
num = num % 3
``` = ```pscode
num = 8
ans = num/3
num%=3

Sine (sin), Cosine (cos), Tangent (tan), Cosecant (csc), Secant (sec), and Cotangent (cot): sin of 30, cos of 60, tan of 20, csc of 50, sec of 70, cot of 40

Sine inverse (sin^-1), Cosine inverse (cos^-1), Tangent inverse (tan^-1), Cosecant inverse (csc^-1), Secant inverse (sec^-1), and Cotangent inverse (cot^-1): sin^-1 of 30, cos^-1 of 60, tan^-1 of 20, csc^-1 of 50, sec^-1 of 70, cot^-1 of 40 (or **) (NOTE: to the power of doesn't work here).

Concatination: "Hello" " " "World" results in "Hello World" num = 10; "Hello the number is {num}" results in "Hello the number is 10"

Comparison Operators

Equal to: x equals y or x is equal to y or x == y Not equal to: x does not equal y or x is not equal to y or x != y Greater than: x is greater than y or x > y Less than: x is less than y or x < y Greater than or equal to: x is greater than or equal to y or x >= y Less than or equal to: x is less than or equal to y or x <= y

Example:

if age >= 18
    output "You are an adult"
else
    output "You are a minor"

Logical Operators

AND: condition1 AND condition2 or condition1 and condition2 or condition1 && condition2 OR: condition1 OR condition2 or condition1 or condition2 or condition1 || condition2 NOT: NOT condition or not condition or !condition

Examples:

if age >= 18 AND age < 65
    output "You are a working-age adult"

if username == "" OR password == ""
    output "Please fill in all fields"

if NOT isLoggedIn
    output "Please log in first"

Conditional Statements (if, else if, else, switch)

Check if currentNumber is equal to 5, if so print hi 5, if not check if it is equal to 7, if so print hi 7, if not print hi not 5 or 7:

if currentNumber equals 5 // or if currentNumber is equal to 5
    output "hi 5"
else if currentNumber equals 7 // or elif, elseif
    output "hi 7"
else
    output "hi not 5 or 7"

Check if currentNumber is greater than 5:

if currentNumber is greater than 5
    output "hi 5"

Check if currentNumber is less than or equal to 7:

if currentNumber is less than or equal to 7
    output "hi 7"

Take a user's input for a desired menu option, check for each case, and print out that number (switch):

/*
    Output:

    Options:
    1. Book a ticket
    2. Cancel a ticket
    3. View a ticket
    4. View all tickets
    5. Track train
    6. Track all trains
    9. Exit

    Please enter an option:
*/
output "Options: "
output "1. Book a ticket"
output "2. Cancel a ticket"
output "3. View a ticket"
output "4. View all tickets"
output "5. Track train"
output "6. Track all trains"
output "9. Exit"
output ""
output "Please enter an option: "
input userOption

switch userOption
    case 1
        output 1
        jump // or break
    case 2
    output 2
        jump
    case 3
        output 3
        jump
    case 4
        output 4
        jump
    case 5
        output 5
        jump
    case 6
        output 6
        jump
    case 9
        output 9
        exit // or stop, return
    default
        output "not " 1 ", " 2 ", " 3 ", " 4 ", " 5 ", " 6 ", or " 9

Loops (for, while, loop)

Basic loop:

loop from 1 to 10 using i {
    output i
    output ""
}

While loop:

i = 0
while i is less than or equal to 10
    i = i+1 // or i++

For loop:

for all the integers between 1 and 10 using i:
    output "Haha " i " love you!"

Do-While loop (executes at least once):

do {
    output "Enter a positive number: "
    input num
} while num <= 0

Repeat-Until loop (executes until condition is true):

repeat {
    output "Enter password: "
    input password
} until password == "secret"

Loop Control

Break out of the loop early:

for i from 1 to 100 {
    if i == 50 {
        jump  // or break
    }
    output i
}

Skip to next iteration:

for i from 1 to 10 {
    if i % 2 == 0 {
        skip  // or continue
    }
    output i  // only outputs odd numbers
}

Arrays and Lists

Declare an empty array:

numbers = []
names = array()

Declare an array with initial values:

numbers = [1, 2, 3, 4, 5]
fruits = ["apple", "banana", "orange"]

Access array element (0-indexed):

firstFruit = fruits[0]  // "apple"
thirdNumber = numbers[2]  // 3

Modify array element:

fruits[1] = "grape"  // changes "banana" to "grape"

Array length:

count = length of numbers  // or count = numbers.length

Add an element to the end of an array:

append 6 to numbers  // or numbers.append(6) or numbers.push(6)

Remove element from array:

remove element at index `2` from numbers  // or numbers.remove(2)

Insert element at specific position:

insert "pear" at index `1` in fruits  // or fruits.insert(1, "pear")

Check if element exists in array:

if "apple" is in fruits
    output "We have apples!"

Loop through array:

for each fruit in fruits
    output fruit

for i from 0 to length of numbers - 1
    output numbers[i]

Sort array:

sort numbers in ascending order  // or numbers.sort()
sort fruits in descending order  // or fruits.sort(descending)

Multi-dimensional Arrays

Declare a 2D array:

grid = [[1, 2, 3], [4, 5, 6], [7, 8, 9]]

Access 2D array element:

value = grid[1][2]  // gets 6 (row 1, column 2)

Loop through 2D array:

for each row in grid
    for each value in row
        output value

Functions

Basic function definition:

function hello takes in nothing
    return "world"
``` or ```pscode
function hello
    return world

Simple addition function:

function add takes in num1 and num2
    return num1 + num2

Function with no return value (procedure):

function printGreeting takes in name
    output "Hello, " name "!"

Calling a function:

result = add(5, 3)  // or result = run add with 5 and 3
output result  // outputs 8

printGreeting("Alice")  // or run printGreeting with "Alice"

Alternative function calling syntax:

sum = run add with 10 and 20
run printGreeting with "Bob"

Records/Structures

Define a record/structure:

record Person
    string name
    number age
    string email

Create and use a record:

person1 = new Person
person1.name = "Alice"
person1.age = 30
person1.email = "alice@example.com"

output person1.name  // "Alice"

Or with initialization:

person2 = Person("Bob", 25, "bob@example.com")

Array of records:

people = [
    Person("Alice", 30, "alice@example.com"),
    Person("Bob", 25, "bob@example.com")
]

for each person in people
    output person.name

Common Built-in Functions

Math Functions

absolute = abs of -5  // or abs(-5)  // 5
rounded = round 3.7  // or round(3.7)  // 4
roundedDown = floor 3.7  // or floor(3.7)  // 3
roundedUp = ceil 3.2  // or ceil(3.2)  // 4
squareRoot = sqrt of 16  // or sqrt(16)  // 4
maximum = max(5, 10, 3)  // or run max with 5 and 10 and 3  // 10
minimum = min(5, 10, 3)  // or run min with 5 and 10 and 3  // 3
randomNum = random()  // or run random  // random float between 0 and 1
randomInt = random integer from 1 to 10  // random int in range

String Functions

text = "Hello World"
textLength = length of text  // or text.length  // 11
uppercase = text to uppercase  // "HELLO WORLD"
lowercase = text to lowercase  // "hello world"
substring = substring of text from 0 to 5  // "Hello"
trimmed = trim(text)  // removes leading/trailing whitespace
splitWords = split text by " "  // ["Hello", "World"]
joined = join ["Hello", "World"] with " "  // "Hello World"

// Character access
firstChar = text[0]  // "H"

// Find substring
position = find "World" in text  // returns 6
contains = text contains "World"  // returns true

Type Checking

isNum = is number(value)  // or run is number with value
isString = is string(value)  // or run is string with value
isBoolean = is boolean(value)  // or run is boolean with value
isArray = is array(value)  // or run is array with value

Error Handling

Try-catch block:

try
    result = 10 / 0
catch error
    output "An error occurred: " error
finally
    output "This always executes"

File Operations (Optional)

Open and read from a file:

open file "data.txt" for reading as fileHandle
while not end of fileHandle
    line = read line from fileHandle
    output line
close fileHandle

Write to a file:

open file "output.txt" for writing as fileHandle
write "Hello, World!" to fileHandle
close fileHandle

Append to a file:

open file "log.txt" for appending as fileHandle
write "New log entry" to fileHandle
close fileHandle

Common Algorithm Examples

Linear Search

function linearSearch takes in array and target {
    for i from 0 to length of array - 1 {
        if array[i] equals target {
            return i
        }
    }
    return -1  // not found
}

Binary Search (on sorted array)

function binarySearch takes in array and target {
    left = 0
    right = length of array - 1

    while left <= right {
        mid = floor((left + right) / 2)

        if array[mid] equals target {
            return mid
        } else if array[mid] < target {
            left = mid + 1
        } else {
            right = mid - 1
        }
    }

    return -1  // not found
}

Bubble Sort

function bubbleSort takes in array {
    n = length of array

    for i from 0 to n - 1 {
        for j from 0 to n - i - 2 {
            if array[j] > array[j + 1] {
                // Swap elements
                temp = array[j]
                array[j] = array[j + 1]
                array[j + 1] = temp
            }
        }
    }

    return array
}

Find Maximum in Array

function findMax takes in array {
    if length of array equals 0 {
        return null
    }

    max = array[0]
    for each value in array {
        if value > max {
            max = value
        }
    }

    return max
}

Best Practices

1. Use meaningful variable names: studentCount instead of sc
2. Keep functions small and focused on one task
3. Comment complex logic
4. Initialize variables before using them
5. Check for edge cases (empty arrays, division by zero, etc.)
6. Use constants for values that don't change
7. Indent code properly to show structure
8. Validate user input before processing