CHAPTER 5: SYSTEM SOFTWARE

5.1 OPERATING SYSTEMS

5.1.1 Need for Operating System

Definition: A set of programs designed to run in the background on a computer system.

Functions:

• Controls operation of computer system
• Provides user interface
• Controls how computer responds to requests
• Controls how hardware communicates
• Provides environment for application software

Why OS is Essential:

• Hardware is unusable without OS
• Acts as interface between user and hardware
• Manages communication between components

5.1.2 Key Management Tasks

Memory Management:

• Memory protection (ensures programs don't use same memory)
• Paging (uses virtual memory)
• Memory allocation

File Management:

• Provides file naming conventions
• Maintains directory structure
• Allocates space to files
• File access control

Security Management:

• Provides usernames & passwords
• Ensures data privacy
• Prevents unauthorized access
• Carries out automatic backup

Hardware Management:

• Installation of driver software
• Controls access to peripherals
• Handles interrupts from devices

Process Management:

• Enables multiprogramming and multitasking
• Resolves conflicts when processes need same resource
• Methods: Round-robin, priority scheduling

5.1.3 Utility Software

Disk Formatter:

• Prepares hard disk for data storage
• Deletes existing data
• Creates sectors and tracks

Virus Checker:

• Checks for viruses
• Removes viruses found
• Monitors incoming/outgoing files

Defragmentation Software:

• Reorganizes files to contiguous sectors
• Reduces read/write head movements
• Improves performance

Disk Repair Software:

• Visualizes disk space usage
• Reports errors (bad sectors)
• Attempts to fix issues

File Compression:

• Reduces file size
• Removes redundant data
• Improves storage efficiency

Backup Software:

• Makes copies of files
• Stores on different medium
• Provides synchronization between devices

5.1.4 Program Libraries

Definition: Pre-written code that can be linked to software under development.

Benefits:

• Saves time (less code to write)
• Smaller testing time (pre-tested)
• Complex algorithms available without understanding implementation

DLL (Dynamic Link Library):

• Shared library file containing code and data
• Loaded to memory only when required
• Available to several applications simultaneously
• Reduces .EXE file size

5.2 LANGUAGE TRANSLATORS

5.2.1 Assembler

Purpose: Translates assembly language to machine code (binary).

Characteristics:

• One-to-one relationship with machine code
• Simple translation process

5.2.2 Compiler vs Interpreter

5.2.3 Two-Step Translation (Java)

Process:

1. Java compiler translates source code to bytecode
2. Java Virtual Machine (JVM) interprets bytecode to machine code

Benefits:

• Platform independence (write once, run anywhere)

5.2.4 IDE Features

Coding Features:

• Context-sensitive prompts
• Variable highlighting (undeclared/unassigned)
• Autocomplete

Error Detection:

• Dynamic syntax checking
• Type checking
• Parameter checking

Presentation:

• Prettyprint (automatic indentation, colour-coding)
• Expand and collapse code blocks

Debugging:

• Single stepping (execute line-by-line)
• Breakpoints (pause at specific line)
• Variables/expressions report window