Software Systems - 1.5

Difference between Systems Software and Application Software?

Systems:

• A systems software is a type of software that controls a computer's software

• Provides an interface between the user of the computer and the hardware

Applications:

• Helps the user to carry out a task e.g. Write a program, Play a game, Make a PowerPoint

Summarise the key tasks which an operating system carries out:

1. Providing a user interface

2. Memory management 

3. Peripheral/Device management 

4. Disk management (secondary storage)

5. Security - Usernames, Passwords, Access Levels

6. File management - creating folders, moving files etc

7. Process management (multi-tasking)

What is a user interface?

 A medium through which the User can interact with the Computer

What type of interface is this?

Command Line

What type of interface is this?

GUI (WIMP)

What type of interface is this?

Menu Driven

What type of interface is this?

Natural Language

Summarise the main aspects of memory management:

• Transfers programs from secondary storage from RAM

• Allocates memory locations to programs in RAM

• Removes unused programs from RAM, possibly transferring to Virtual Memory

• Keep track of memory locations where programs are stored. Memory can become fragmented

What is a process?

A program running in RAM (main memory)

How is multitasking achieved by an operating system?

The processor allocates time slices to each process in quick succession. It happens so quickly, the user perceives that processes are being executed simultaneously

Explain why multitasking is needed in an operating system?

So the user is able to execute more than one program  at a time (apparently)

What is a peripheral device?

A device outside the CPU but under its control

What is a device driver?

A small program which acts as an interface between the peripheral device and the operating system. It ensures the operating system can send commands to the printer using instructions that it will understand. This allows the OS to communicate with printers from different manufacturers

What role does an operating system play with peripheral management and device drivers?

1. User gives command to print

2. Operating system takes over and communicates the print job to the relevant device driver

3. The device driver then instructs the printer to carry out the print job

Summarise the key aspects of user management which operating systems provide:

• It retains settings for users such as icons, desktop backgrounds

• Provides access rights to files and programs 

• Allows users to create multiple user accounts 

• Lock out after a repeated incorrect password attempt

• Monitor user activity

 Summarise the key aspects of file management which operating systems provide:

• Associate programs with file extensions e.g .Doc files open in a Word Processor

• Rename files

• Delete files

• Move files to different folders

• Create a folder

• Restore deleted files out of the bin

• Copy and paste files

What is a utility program?

Carry out specific tasks related to managing computer system resources. Usually non-essential, are included in the OS or obtained separately

Explain what encryption tools can do:

Encryption tools can help to keep   sensitive    data safe from cyber   criminals   or unauthorised access.

It can also be used to protect    backup   copies of data kept on   offline   storage.

Copies of sensitive information stored on flash memory sticks or laptops and removed from the office could be vulnerable to carelessness or theft and so encrypting the data will make sure it does not fall into the wrong hands. 

The encryption process uses an algorithm   and a    key  to transform plaintext   into ciphertext . To decode the original information, it would be necessary to know both of these.

Look at image:

Haven’t looked at it good enough

Why do hard disks become fragmented?

When files are deleted, unused blocks of memory locations become available for use. These can become fragmented/distributed across the device

If a new large file is to  be written to the drive it ends up being saved using free memory blocks which are not together/ adjacent/ contiguous

What does a disk defragmentation utility do?

1. Reorganises  the files on the disk service to ensure that they occupy contiguous memory locations

2. Creates one contiguous block of available memory

What are the benefits of defragmentation of a hard disk?

1. Improves the speed of accessing or opening data files and saving data files

2. Extends the lifespan of the harddisk as read-write heads do not have to work as hard

3. Programs will run faster

What is data compression?

Reducing the file size

What are the two types of compression called?

Lossy and Lossless

State the difference between the two:

Lossy - Actual data is removed from the file and the original file can never be restored e.g. JPEG compression for images

Lossless - Actual data is not removed from the file, instead redundant data is removed from the file, so that the file can be restored to the original e.g. ZIP format

State three examples of situations where data compression is useful:

1. Streaming services and their videos

2. Limited local storage remaining - e.g. On a hard disk

3. Storing backups/archives

4. Downloading large files on the internet

5. Reducing the size of email attachments/ file sizes

State an example of one file format which can be used to compress data using lossless compression:

ZIP format