Programming

8.1 Programming concepts

Variables and Constants

A variable is a named data store that contains a value that may change during the execution of a program.

A constant is a named data store that contains a value that does not change during the execution of a program. The value only needs to be changed once, if circumstances change.

Pseudocode:

DECLARE Num1 : INTEGER
Num1 ← 30

CONSTANT Constant1 ← 500

Python:

Num1 = 30
Constant1 = 500

Basic Data Types

The purpose of data types in programming is to specify the type of data that can be stored and manipulated within a program. For example, mathematical calculations can only be performed on integers and float values.

Pseudocode:

DECLARE Number1 : INTEGER
DECLARE RealNumber : REAL
DECLARE Text1 : STRING
DECLARE Character1 : CHAR
DECLARE BooleanValue : BOOLEAN

Python:

Number1 = 4
RealNumber = 3.4
Text1 = "Note Academy"
Character1 = "E"
BooleanValue = True

Python does not differentiate between single quotes and double quotes.

Input and Output

Pseudocode:

OUTPUT "Please enter your name: "
INPUT Name

Python:

firstname = input("Please enter your name: ")
print("My name is ", firstname)

To only output something, use the print function. Use a comma to combine variables and strings. Remember to use speech marks.

Selection Statements

IF ELSE statement

if NameOfAcademy == "Note Academy":
    print("The best academy to ever exist. Period.")
else:
    print("Nope, not even close to Note Academy.")

MATCH CASE statement

match grade:
    case "A":
        print("Grade = A")
    case "B":
        print("Grade = B")
    case "C":
        print("Grade = C")
    case _:
        print("Failureeeee")

Loops

Count-controlled loop (FOR loop)

for x in range(10):
    print("-")

These are the three ways you can use the range function. The step parameter is used to set the increment or decrement. By default, which is the third one in the examples above, the range function starts at 0 and ends at stop − 1. The loop in the example will use the values 0 1 2 3 4 5 6 7 8 9, so it prints the dash 10 times.

Pre-condition loop (WHILE loop)

x = 0
while x < 10:
    print("Note Academy = Success")
    x = x + 1

String Handling

Finding the length

Pseudocode:

LENGTH("Note Academy")
LENGTH(Name)

Python:

len("Note Academy")
len(Name)

Output: 12

Substring

Pseudocode:

SUBSTRING("Note Academy", 1, 4)
SUBSTRING(String1, 1, 4)

Python:

"Note Academy"[0:4]
String1[0:4]

Output: "Note"

Upper

Pseudocode:

UCASE("Note Academy")
UCASE(String1)

Python:

"Note Academy".upper()
String1.upper()

Output: "NOTE ACADEMY"

Lower

Pseudocode:

LCASE("Note Academy")
LCASE(String1)

Python:

"Note Academy".lower()
String1.lower()

Output: "note academy"

Operators

Subroutines: Functions and Procedures

A subroutine is a sub-program that performs a frequently used operation within a program. It can be called when needed and can be reused by another program.

Procedures and functions are both subroutines. However, in contrast to procedures, functions always return a value.

Both functions and procedures can have parameters. Parameters are variables used to accept input values when a subroutine is called. They allow subroutines to be flexible and reusable by operating on different data inputs.

Procedure (without parameters)

Pseudocode:

PROCEDURE Greetings
    OUTPUT "Hello. Welcome to Note Academy."
ENDPROCEDURE

CALL Greetings

Python:

def Greetings():
    print("Hello. Welcome to Note Academy.")

Greetings()

Output: Hello. Welcome to Note Academy.

Procedure (with parameters)

Pseudocode:

PROCEDURE Division(Num1 : INTEGER, Num2 : INTEGER)
    OUTPUT Num1 / Num2
ENDPROCEDURE

CALL Division(30, 5)

Python:

def Division(Num1, Num2):
    print(Num1 / Num2)

Division(30, 5)

Output: 6 (Python prints 6.0, because / always gives a float)

Function

Pseudocode:

FUNCTION Division(Num1 : INTEGER, Num2 : INTEGER) RETURNS REAL
    RETURN Num1 / Num2
ENDFUNCTION

DECLARE answer : REAL
answer ← Division(30, 5)
OUTPUT answer

Python:

def Division(Num1, Num2):
    return Num1 / Num2

answer = Division(30, 5)
print(answer)

It must be kept in mind that the arguments, which are the actual values or data passed to a subroutine's parameters when the subroutine is called, should be of the same data type according to which the function was made. For example, if you pass text as an argument, it will give an error.

The first line in which the function or procedure is declared is called the header.

Local and Global Variables

Local variables are defined within a function or block and can only be accessed within that function or block.

Global variables are defined outside of any function and can be accessed by any part of the program.

global_var = "I am global"

def example_function():
    local_var = "I am local"
    print(local_var)
    print(global_var)

example_function()
print(global_var)
print(local_var)

Output:

I am local
I am global
I am global
Error

global_var is a global variable accessible both inside and outside example_function.

local_var is a local variable accessible only within example_function. Attempting to access it outside the function will result in an error as shown above.

Library Routines

Library routines are pre-written subroutines that are available for use by programmers. Using library routines can save time and effort, as programmers can leverage existing, tested code instead of writing these functions from scratch.

Pseudocode:

Num1 ← MOD(7, 3)       // returns the remainder
Num2 ← DIV(7, 3)       // returns the quotient
Num3 ← ROUND(3.142, 1) // rounds it to 1 decimal place
Num4 ← RANDOM()        // generates a random number between 0 and 1
OUTPUT Num1, ",", Num2, ",", Num3, ",", Num4

Python:

Value1 = 7 % 3         # MOD
Value2 = 7 // 3        # DIV
Value = divmod(7, 3)   # returns 2 numbers, div and then mod
Value3 = round(3.142, 1)
from random import random
Value4 = random()
print(Value1, ",", Value2, ",", Value3, ",", Value4)

In pseudocode, use 2 forward slashes to start a comment. In Python, use a hash to start a comment.

8.2 Arrays

Arrays

Arrays are used to store and manage collections of data, particularly when dealing with multiple values of the same type. They allow efficient access and manipulation of data using indices.

One-dimensional array

1D arrays are like lists. They store multiple values of the same type in one variable.

Pseudocode:

DECLARE Array1 : ARRAY[0:3] OF INTEGER
Array1[0] ← 5
Array1[1] ← 9
Array1[2] ← 7
Array1[3] ← 3
FOR i ← 0 TO 3
    OUTPUT Array1[i]
NEXT i

Python:

Array1 = [5, 9, 7, 3]
print(Array1)

Output: [5, 9, 7, 3]

Two-dimensional array

2D arrays are collections of elements arranged in rows and columns, forming a grid. They are useful for representing matrices or tables.

Pseudocode:

DECLARE Array1 : ARRAY[0:2, 0:1] OF INTEGER
Array1[0,0] ← 1    // Array[rows, columns]
Array1[0,1] ← 2
Array1[1,0] ← 3
Array1[1,1] ← 4
Array1[2,0] ← 5
Array1[2,1] ← 6
FOR RowCounter ← 0 TO 2
    FOR ColumnCounter ← 0 TO 1
        OUTPUT Array1[RowCounter, ColumnCounter]
    NEXT ColumnCounter
NEXT RowCounter

Python:

Array1 = [[1, 2], [3, 4], [5, 6]]
print(Array1)

Output: [[1, 2], [3, 4], [5, 6]]

Tap to enlarge

A one-dimensional array with indexes 0 to 3 and a two-dimensional array of three rows and two columns

Close

8.3 File handling

File Handling

Files can be used to save data between program executions, ensuring that information is not lost when the program is closed. They can also handle large amounts of data that may not fit into the program's memory at once.

Pseudocode:

DECLARE Line1 : STRING
DECLARE File1 : STRING
File1 ← "NoteAcademy.txt"

OPEN File1 FOR WRITE         // opens the file in write mode

OUTPUT "Enter a line of text: "
INPUT Line1

WRITEFILE File1, Line1       // stores Line1 in the file

CLOSEFILE File1              // closes the file

OPEN File1 FOR READ          // opens the file in read mode

READFILE File1, Line1        // stores the line from the file into Line1
OUTPUT Line1

CLOSEFILE File1

Python:

File1 = open("NoteAcademy.txt", "w")
Line1 = input("Enter a line of text: ")
File1.write(Line1)
File1.close()
File1 = open("NoteAcademy.txt", "r")
Line1 = File1.read()
print(Line1)
File1.close()

Tap to enlarge

Writing to a file with OPEN, WRITEFILE and CLOSEFILE, then reading it back with OPEN, READFILE and CLOSEFILE

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