4 software

SYSTEM SOFTWARE

is essential for the operation of the computer system

It gives users a platform to run applications and carry out tasks

Software is categorized into system software and application software:

Examples of software:

General features of system software:

• A set of programs to control and manage the operation of computer hardware

• Provides a platform on which software can be run

• Controls allocation and usage of hardware resources

General features of an application software:

• Used to perform various applications (apps) on a computer

• Allows a user to perform specific tasks using the computer’s resources

• May be a single program or a suite of programs

System software consists of?

1. Utility Software

2. Operating System

UTILITY SOFTWARE

A software designed to help maintain, enhance, and troubleshoot/repair a computer system

• Designed to perform a limited number of tasks

• Interacts with a computer's hardware, for example, secondary storage devices

• Some utility software is installed with the operating system

Examples of a utility software

• Defragmentation software (maintain)

• Compression (enhance)

• Encryption (enhance)

• Task manager (troubleshoot/repair)

APPLICATION SOFTWARE

A software chosen by a user to help them carry out a specific task, specific to them

• Installed on top of system software and is user-chosen to best suit individual preferences

Examples of an application software

• Productivity (get things done efficiently using spreadsheets or presentations)

• Communication (email, browser, messaging)

• Entertainment (movies, games, music)

Utility system - Disk defragmentation

Utility system - Disk cleanup

Disk drives do not need actual cleaning as they are sealed; however, disk clean-up tools help to improve free space and system performance by:

• Deleting temporary files

• Clearing cached files for a web browser

• Removing unnecessary program files

Utility system - Backup and antivirus software

Hard drives sometimes fail and may also be stolen, and therefore need to be regularly backed up to external drives or cloud backup services

Antivirus software scans computers to make sure that they don't contain viruses

Examples of an operating system

OPERATING SYSTEM

A software that manages computer hardware and provides a platform for running applications

Provides an interface between the user and the hardware in a computer system

• Hides the complexities of the hardware from the user

Main functions of an operating system

Managing files, providing an interface, managing peripherals and drivers, managing memory, managing multitasking, providing a platform for running applications, providing system security, and managing user accounts

OS - File Management

A process carried out by the operating system, creating, organizing, manipulating, and accessing files and folders on a computer system

File management gives the user the ability to:

• Create files/folders

• Name files/folders

• Rename files/folders

• Copy files/folders

• Move files/folders

• Delete files/folders

The Operating System allows users to control who can access, modify, and delete files/folders using permissions

The Operating System provides a search facility to find specific files based on criteria

OS - Handling Interrupts

Interrupt events require the immediate attention of the CPU

• To maintain the smooth running of the system, interrupts need to be handled and processed promptly

OS - User Interface

How the user interacts with the operating system

Examples of user interfaces include:

• Command Line Interface (CLI)

• Graphical User Interface (GUI)

• Menu

• Natural Language (NL)

OS - User Interface - Command Line Interface

Requires users to interact with the operating system using text-based 

commands

• CLIs are more commonly used by advanced users, as specific commands are needed

• Examples: MS-DOS (Microsoft Disk Operating System) and Raspbian (Raspberry Pi)

OS - User Interface - Graphical User Interface

Requires the users to interact with the operating system using visual 

elements such as windows, icons, menus, and pointers

• Optimised for mouse and touch gesture input

• Examples: Windows, MAC OS, Android

OS - User Interface - Menu-driven Interface

A successive menu presented to a user with a single option at each stage

Often performed with buttons or keypads

OS - User Interface - Natural Language Interface 

Uses the spoken word to respond to spoken or textual input from a user

• Examples: Virtual assistants (Siri, Alexa), search engines, smart home devices

WIMP interfaces 

OS - Peripheral Management and Device Drivers

A peripheral device adds functionality to the hardware, which interacts with the software

• The Operating System allocates resources to peripherals to ensure efficient operation

• Makes use of plug-and-play (PnP), automatically detecting and configuring new peripherals

OS - Peripheral Management and Device Drivers - Device Driver

A piece of software used to control a piece of hardware

• Peripherals require device drivers to be used by the operating system

• A separate device driver needs to be downloaded to make use of its maximum capacity

OS - Memory Management

A process carried out by the operating system, allocating main memory (RAM) between different programs that are open at the same time

• To run a program, the computer must copy each program from storage into main memory

  • Data used by the program is also copied into main memory

  • The operating system keeps a record of where each program and its data are located

  • The operating system also makes sure that the program does not overwrite existing programs

OS - Multi-tasking

The process of using or running several programs at the same time

• Each program is given a short time on the CPU before it is paused by the operating system

• The operating system then allows the next program to make use of the CPU for a short time

• By switching quickly between programs, it appears to the user that all of them are happening at the same

OS - Providing a Platform for Running Applications

This can be done by allowing software access to system resources

OS - Providing System Security

Operating systems provide various security features such as password-protected system accounts, a firewall (montiors incoming and outgoing network traffic), virus scanning and file encryption

• System accounts can also be restricted from performing certain actions

OS - User Management

A process carried out by the operating system enabling different users to log onto a computer

• The Operating System is able to maintain settings for individual users, such as desktop backgrounds, icons and colour schemes

A system administrator is able to locate different access rights for different users on a network

How Do Application, OS, and Hardware Communicate?

• Application software talks to the Operating System, allowing it to interact with the hardware

• The hardware then processes and sends information to the Operating System, which talks directly to the application software

The process is repeated while the application software is in use

FIRMWARE

an embedded software within the hardware of a device, to make it function. Contains programs that are stored permanently in hardware

• The BIOS stored on a computer is stored on a flash ROM

• It can be updated by flashing the ROM

BOOTLOADER 

INTERRUPTS

a signal sent from a device by software to the microprocessor. This will cause the microprocessor to STOP what it is currently doing

• Example: Printers sending a signal notifying the user that there is no paper, ink, etc

What happens when the CPU is interrupted, and how does it handle the interrupt?

• The CPU runs an Interrupt Service Routine (ISR), also called an interrupt handler.

• The ISR executes as quickly as possible because it pauses the CPU’s current task.

• The ISR contains instructions that must be fetched, decoded, and executed to deal with the interrupt.

• To prevent data loss, the contents of CPU registers are copied to a reserved area in RAM called the stack.

• Data is pushed onto the top of the stack for safe storage and retrieved once the interrupt is complete, allowing the CPU to resume its previous task.

2 Types of Interrupts - Hardware interrupts 

• The power button may have been pressed

• Moving the mouse

• Clicking on an icon to open a new program

• Keyboard presses, e.g, ctrl, alt, delete

  • The interrupts are sent via Interrupt Request Lines (IRQ)

    • When a mouse is moved, constant interrupts are sent to the computer so that it is able to update the location of the pointer

    • Same with keyboards, pressing a specific key

2 Types of Interrupts - Software interrupts 

• A program is not responding

• Division by zero

• Two processes are trying to access the same memory location

  • Generated by programs that are running

    • For instance, if a program tries to divide by zero, a ‘division by zero’ interrupt will need to be handled

2 Types of Interrupts - Software interrupts - How do software interrupts deal with faults 

• Software interrupts deal with faults such as:

  • Page faults - this is when data is not inside RAM, but in virtual memory, and needs to be loaded back into RAM

  • Segmentation faults - this is when one program tries to make an illegal memory location, such as the memory used by another program

• When a fault occurs, an interrupt service routine is called

Generations of programming languages can be split into two categories…

Low level

• First generation

• Second generation

High level

• Third generation

LOW-LEVEL LANGUAGES

A programming language that directly translates to machine code, which is understood by a processor

• Allow direct control over hardware such as memory and registers

Written for specific processors to ensure they embed into the correct machine architecture

Low-level - FIRST GENERATION

• Machine code

• Instructions are directly executable by the processor

• Written in binary code

Low-level - SECOND GENERATION

• Assembly code

• Written using mnemonics, abbreviated text commands such as LDA (Load), STA (Store)

• Using assembly code can write human-readable programs that correspond to the machine code

• Needs to be translated into machine code for the computer to be able to execute it

Advantages and disadvantages of second generation 

HIGH-LEVEL LANGUAGES

A programming language that uses English-like statements to allow users to program with easy-to-use code

• Allow for clear debugging

• Easier to maintain programs

• Needed due to the development of processor speeds and the increase in memory capacity

• One instruction translates into many machine code instructions

• Needs to be translated into machine code fo the computer to be able to execute it

• EXAMPLES:

  • Python

  • Java

  • Basic

  • C++

Advantages and disadvantages of high-level languages 

Students sometimes confuse machine code and assembly. Remember:

Machine code = binary (1st generation)

Assembly = mnemonics (2nd generation, needs assembler)

What is assembly language, and why do programmers use it?

• Assembly language is a second-generation, low-level language that simplifies writing machine code instructions.

• Programmers use it to:

  • Access or control specific hardware components.

  • Execute machine-dependent instructions.

  • Minimize memory (RAM) usage.

  • Increase execution speed of programs.

How does assembly language work using mnemonics and an assembler?

• Assembly language uses mnemonics (e.g., ADD, MOV) to represent machine code instructions.

• It lets programmers work directly with hardware while reducing complexity.

• When a mnemonic is read, it’s looked up in a table.

• An assembler converts the mnemonic into its corresponding binary (machine) code.

• If a match is found, the mnemonic is replaced with the correct binary sequence.

TRANSLATOR

a program that translates program source code into machine code so that it can be executed directly on a processor

• Low-level languages such as assembly code are translated using an assembler

• High-level languages such as Python are translated using a compiler or interpreter

COMPILER

translates high-level language program (the source code) into machine code all in one go 

• Generally used when a program is finished

• Produces an executable file which means the file can be executed

• If the compiler encounters a syntax error, it cannot translate the statement so no object code is produced

  • It provides an error report for all errors that are detected in code

ALTOGETHER

Advantages and disadvantages of using a compiler 

INTERPRETER

 translates high-level languages into machine code one line at a time

• Continues like this, translating and executing the code line-by-line

• If syntax is encounrtered, it displays an error message and stops executing the program

LINE-BY-LINE

Advantages and disadvantages of using an interpreter

Main advantages and disadvantages of assembly, compiler and interpreter 

The advantages and disadvantages of a compiler and interpreter - what should you use?

IDE, INTEGRATED DEVELOPMENT ENVIRONMENTS

a software designed to make writing high-level languages more efficient 

IDE - Line numbers

Allow a programmer to clearly see each new line of code

• When errors are found, the line number that they occur on will also be stated

• In some IDEs, parts of the program that the programmer doesn’t need to see can be folded

IDE - Syntax highlighting

Where the colour of the text changes to show different parts of a program

IDE - Prettyprint

Applies indentation and formatting to the code

• Makes it easier for other programmers to read

• It also makes code consistent across different programs

  

IDE - Error diagnostics

Help programmer to find where they made a mistake

• Errors are identified along with the line number that they occur on

• The code may be underlined or highlighted to show the error

IDE - Debugging code

Breakpoints are set by the programmer so that the IDE stops the program mid-way through running

• The programmer can step through code line by line

• They can watch variables as they change

IDE - Run-time Environment

Allows a programmer to test their program while it is running

• If the program crashes the run-time environment can see what happened and give useful information to the programmer

• Libraries that come with the programming language will be available to the programmer to use

IDE - Translators

IDEs will contain necessary translators to run and test the code

• The IDE may compile the code or interpret it by running it line by line - this is very helpful for debugging the code

IDE - Auto-completion and correction

Gives the programmer suggestions for variable names and keywords as they type

• Improves the speed a programmer writes a program

• Tabs, brackets and braces may also be added automatically to the code to save the programmer time

• Some IDEs have auto-correction which fixes mistakes such as those made in keywords

Summary of all features of IDE