Data Types and Programming Techniques

This section explains Data Types and Programming Techniques focusing on Data types, Casting, String manipulation, Basic file handling operations, The use of records to store data and SQL, Arrays, Using subprograms to produce structured code, Random number generation.

Data Types

Data types define the kind of data a variable or constant can hold. Common data types include:

• Integer: Whole numbers (e.g., 5, -10).
• Float/Real: Numbers with decimal points (e.g., 3.14, -0.5).
• Boolean: True/False values (e.g., True, False).
• String: Text (e.g., "Hello, world!").
• Character: A single letter, digit, or symbol (e.g., 'A', '1').

Casting

Casting is the process of converting a variable from one data type to another.

Examples:

python

int("5") # Converts a string "5" to an integer

float(10)  # Converts an integer 10 to a float

str(3.14)  # Converts a float 3.14 to a string

String Manipulation

Strings are sequences of characters and can be manipulated using various techniques.

Length: Find the number of characters in a string.

python

len("Hello")  # Result: 5

Character Position: Retrieve a character at a specific position (indexing starts at 0 in most languages).

python

"Hello"[1]  # Result: 'e'

Upper and Lowercase: Change the case of a string.

python

"hello".upper()  # Result: 'HELLO'

"HELLO".lower()  # Result: 'hello'

Concatenation: Combine two or more strings.

python

"Hello" + " " + "World"  # Result: 'Hello World'
 

Basic File Handling Operations

File handling is used to store, retrieve, and manipulate data in files.

Opening and Closing Files:

python

file = open("example.txt", "r")  # Open in read mode

file.close() # Close the file

Reading from a File:

python

file = open("example.txt", "r")

data = file.read() # Read the entire file

file.close()

End of File:

• Reached when there is no more data to read.
• Typically used in loops to stop reading.

Writing to a File:

python

file = open("example.txt", "w")  # Open in write mode

file.write("Hello, file!")  # Write data to the file

file.close()

Use of Records to Store Data and SQL

Databases, Records, and Attributes

• Database: A structured collection of data.
• Record: A single row in a database table.
• Attribute: A column in a database table (e.g., name, age).

Structured Query Language (SQL)

SQL is used to interact with databases.

Retrieving Data:

sql

SELECT name, age FROM students WHERE age > 16;

Common Commands:

• SELECT: Retrieve data.
• INSERT: Add new records.
• UPDATE: Modify existing records.
• DELETE: Remove records.

Arrays

Arrays are used to store multiple values under a single variable name.

 Declaring an Array

Define an array with a specific size or populate it directly.

python

numbers = [1, 2, 3, 4, 5]  # Declare and assign values

Assigning Values to an Array

Python

numbers[0] = 10 # Assign 10 to the first element

Retrieving Values from an Array

python

print(numbers[0]) # Retrieve the first element

Two-Dimensional Arrays

Arrays within arrays, used for grid-like data.

python

grid = [[1, 2], [3, 4]]  # 2D array

print(grid[0][1]) # Access the second element of the first row

Using Subprograms to Produce Structured Code

Benefits of Using Subprograms

• Makes code reusable and easier to maintain.
• Improves readability by breaking the program into logical sections.
• Reduces duplication of code.

Procedures

Subprograms that perform a task but do not return a value.

python

def greet():

   print("Hello")

Functions

Subprograms that perform a task and return a value.

python

def add(a, b):

    return a + b

Built-in Functions

Predefined functions provided by the programming language.

Examples: len(), range(), abs().

Random Number Generation

Random numbers are often used in games and simulations.

Example:

python

import random

random_number = random.randint(1, 10)  # Generates a random integer between 1 and 10

Summary of Key Concepts

Data Types: Categorise the kind of data stored in variables.

String Manipulation: Includes finding length, accessing characters, and concatenation.

File Handling: Enables reading, writing, and managing files.

Records and SQL: Used for handling structured data in databases.

Arrays: Store multiple values; two-dimensional arrays are used for grid-like structures.

Subprograms: Include procedures and functions, helping to structure code logically.

Random Numbers: Useful for generating unpredictable values.

These concepts are critical for creating efficient and functional programs.