CHAPTER 8: FURTHER PROGRAMMING

8.1 PROGRAMMING PARADIGMS

8.1.1 Low-Level Programming

Characteristics:

Close to machine language
Direct hardware access
Instructions converted to machine code without compiler
Non-portable (specific to processor)
Small memory footprint
Examples: Assembly, Machine code

Addressing Modes:

Immediate: Data is value itself
Direct: Address contains data
Indirect: Address at address contains data
Indexed: Address + index register contents

8.1.2 Imperative (Procedural) Programming

Characteristics:

Sequence of statements changes state
Explicit control flow
Variables modified by assignments
Based on Von Neumann architecture

Examples:

C, Pascal, BASIC
Python (also supports other paradigms)

8.1.3 Object-Oriented Programming (OOP)

Key Terms:

Object: Instance of a class
Class: Blueprint for creating objects
Property/Attribute: Data in object
Method: Function in object
Inheritance: Child class inherits from parent
Polymorphism: Same interface, different behaviour
Encapsulation: Hiding internal details
Containment: Object contains other objects

Inheritance Example:

<PYTHON>

class Person:
 def __init__(self, name, age):
 self.name = name
 self.age = age
 
 def get_name(self):
 return self.name

class Student(Person): # Inherits from Person
 def __init__(self, name, age, student_id):
 super().__init__(name, age) # Call parent constructor
 self.student_id = student_id

8.1.4 Declarative Programming

Characteristics:

States what needs to be done, not how
Non-procedural
Control flow implicit
Backtracking supported

Example:

Prolog
SQL

8.2 FILE PROCESSING

8.2.1 File Modes

Mode	Purpose
READ	Read from file
WRITE	Write to file (overwrites)
APPEND	Add to end of file
RANDOM	Direct access

8.2.2 Serial File Operations

Reading:

<PYTHON>

file = open("data.txt", "r")
while not EOF(file):
 line = READFILE(file)
 process(line)
CLOSEFILE(file)

Writing:

<PYTHON>

file = open("data.txt", "w")
WRITEFILE(file, "data")
CLOSEFILE(file)

8.2.3 Sequential File Operations

Search:

Read records sequentially
Compare key field
Stop when found or key exceeds target

Add:

Read from old file
Write to new file
Insert new record in correct position

Delete:

Read from old file
Write to new file
Skip record to delete

8.2.4 Random File Operations

Hashing:

<TEXT>

Position = Hash(Key) MOD FileSize

Direct Access:

<PYTHON>

SEEK(file, position)
GETRECORD(file, record)
PUTRECORD(file, record)

8.3 EXCEPTION HANDLING

8.3.1 Exceptions

Definition: Runtime errors that cause program to terminate if not handled.

Common Exceptions:

Division by zero
File not found
Invalid input
Memory overflow

8.3.2 Handling Exceptions

Try-Except Structure:

<PYTHON>

try:
 # Code that might cause error
 file = open("data.txt", "r")
 data = file.read()
except FileNotFoundError:
 print("File not found")
except Exception as e:
 print(f"Error: {e}")
finally:
 # Always executes
 if 'file' in locals():
 file.close()

Purpose:

Prevent program crash
Provide meaningful error messages
Allow graceful recovery