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