1.5 Systems Software Flashcards
OCR GCSE Computer Science J277
Operating System
System software that manages hardware, software and resources, and provides services for other software. It will also usually provide an interface for the end user.
OS Major Functions
- User interface
- Peripheral management and drivers
- File management
- Memory management and multitasking
- User management
Utility Software
A subcategory of system software that improves the security or performance of a computer system. Examples include antivirus software and registry cleaners.
Defragmentation Software
Encryption Software
Data Compression Software
They are not essential to the running of a computer, but make specific tasks easier or add an additional layer of housekeeping.
User Interface
Allows the user to interact with the computer. Can be Command Line Interface (CLI) where user types in specific commands, requiring a low amount of storage and RAM. Can be Graphical User Interface (GUI) that allow the user to click on icons and select option from a menu. Can be Natural Language Interface (like Siri) where you can talk to the device.
The OS provides a means of interacting with the computer, often through buttons, keyboard or mice.
An interface may be:
purely text using a command line interface, menu driven,
or a Graphical User Interface (GUI) / WIMP Interface (e.g. Windows, WIMP standards for Windows Icons, Menus and Pointer)
GUI
Graphical User Interface.
A type of interface that allows the user to interact with a computer system. It usually involves clicking on icons or selecting options from a menu.
Windows
Icons
Menus
Pointers (mouse clicks or screen presses)
Also known as a WIMP Interface - Windows, Icons, Menus and Pointer.
CLI
Before GUIs were developed, users had to use the command line interface (CLI).
A CLI allows the user to interact with the system by typing in specific commands.
There are no graphics or icons that you would commonly find on devices such as a smartphone or tablet computer; instead the user enters in text at a command prompt. It is at this prompt that the user is able to issue commands that are executed by the system.
CLIs still tend to be used by network managers who want to do things that are not possible using the standard GUI.
The main benefits of a CLI include the fact that it requires a low amount of secondary storage and RAM as there are no graphics.
Experienced users and system administrators also often prefer to use a CLI as it allows greater control over the computer system than restrictions often applied to a graphical user interface.
Natural Language Interface
This interface involves the user giving instructions for the computer to perform using language you would normally use when speaking to another human being. Unlike the CLI, you don’t need to learn specific commands.
A natural language interface can be text based, but also can be used with audio commands, such as a home personal assistant.
“Hey assistant, turn on the lights in the kitchen, please.”
Multitasking
several programs running at the same time.
Though only one process can be completed at a time, it happens so quickly it appears as if the programs are running simultaneously.
Switching quickly between tasks is known as multitasking.
Modern computers often have multiple cores, which makes them more efficient at multitasking.
However, each core can only carry out one process at a time.
Files and programs need to be in memory for the CPU to perform tasks on them.
The OS moves programs and files in and out of memory (from the hard drive or from virtual memory) so processes tasks as required.
Processor Management
Makes sure that all the hardware is processing the right instructions at the right time. Finds the appropriate data from secondary storage and loads it into main memory (RAM) before the processor is instructed to execute the processes needed to open that program.
When you open a program on a computer, the operating system works behind the scenes to make sure that all the hardware is processing the right instructions at the right time.
To do this, it starts by finding the appropriate data from the secondary storage and loads it into the main memory (RAM).
The Processor is then instructed to execute the processes needed to open that program.
Processor
The part of a computer system that carries out the fetch-decode-execute cycle.
Main memory
A unit with addressable memory locations that can be accessed directly by the processor. Stores data and instructions while they are being processed.
Scheduler
A computer with a single processor Core can only carry out one process at a time;
however, the OS will use a scheduler to swap tasks in and out of the processor so that it appears to the user that the computer is carrying out more than one task at the same time.
Memory Management
Instructions and data needed for a process have to be available in main memory. The memory manager keeps track of what portions of memory have been allocated, maps memory to each process, determines how much memory to allocate each process and determines when a portion of memory should be available for a process.
The Operating System manages the available memory in RAM.
When a program finishes, or data is no longer needed, the memory manager frees up the space in RAM so it can be reused.
You could compare this to a restaurant manager assigning diners to tables in the restaurant, and clearing tables after diners finish their meals so more diners can sit down to eat.
The instructions and data needed for a process have to be available in main memory.
To ensure this, the OS runs a memory manager program, which:
Keeps track of what portions of memory have been allocated
Maps memory to each process
Determines how much memory to allocate to each process
Determines when a portion of memory should be available for a process
Peripheral
Additional hardware devices that are external to the core components of a computer system. These devices can be used for input, output, or data storage.
E.g. Printer
Hardware
The physical components of a computer system.
