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 

 

 

 

 

 Feature 

 Compiler 

 Interpreter 

 

 

 

 

 Translation 

 Translates entire program before execution 

 Translates line-by-line 

 

 

 Output 

 Creates .exe file 

 No .exe created 

 

 

 Execution 

 Faster (already compiled) 

 Slower (translates each time) 

 

 

 Error Reporting 

 All errors at end 

 Stops at first error 

 

 

 Development 

 Used when development complete 

 Used during development 

 

 

 Debugging 

 Difficult (all errors at end) 

 Easier (stops at error) 

 

 

 

 

 

 5.2.3 Two-Step Translation (Java) 

 Process: 

 

 Java compiler translates source code to bytecode 

 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