# 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
FeatureCompilerInterpreter
TranslationTranslates entire program before executionTranslates line-by-line
OutputCreates .exe fileNo .exe created
ExecutionFaster (already compiled)Slower (translates each time)
Error ReportingAll errors at endStops at first error
DevelopmentUsed when development completeUsed during development
DebuggingDifficult (all errors at end)Easier (stops at error)
### 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