What is an operating system

An operating system is the main management system which is loaded after the boot loader has finished. Its responsible has many core responsibilities which allows all the programs to work together as one system. In the layer structure on the right you can see it is the link between the core hardware and the applications that use these pieces of hardware. How input and output devices link to the applications is controlled by this core program.

Device Manager

When a new device is made it has a program to control it, known as a “driver”. This driver is built to become a plug-in to the operating system, allowing the link to be built between the applications and that hardware device. If a device has not got a driver it cannot be used by the applications. Classes of devices however may use the same driver. An example of this is USB mass storage devices. All USB mass storage devices work using a Mass Storage Device Class which is transmitted as a signal when the device is connected. All these devices use the same protocol (A SCSI command set) and therefore can share a general driver. Although this is not a problem with this device, other devices which may have specialist functions or extra commands within their command set may not be able to use them, because the operating system has chosen a general driver

Memory Management

An example of a job fulfilled by an operating system is memory management. This ensures that each application is assigned memory which does not get overwritten by any other program, and for security reasons ensures that other programs cannot read private memory from a particular program (known as memory protection). Without this management programs would overwrite each others memory spaces and would crash each other.

Processor Manager

Another example of a job done by the operating system is the management of interrupts in the fetch execute cycle. As only one action can be performed on each processor core at once it is important that we allow other jobs that may be more important to interrupt a less important job as each job may be a few thousand lines of machine code, the code directly fed into the CPU. The information on jobs like this is kept in an “Interrupt Registry” which controls what processes interrupt when and also when the process is finished which other process gets resumed first. As well as this programs running multiple tasks at once (known as threads) would be controlled to try and give each thread equal time on the processor, known as Time Sharing.

Storage Management

This looks after the hard disks and other storage. It uses the FAT tables to ensure it does not overwrite data, and allows deletion ,copying and moving of data.

API Management

Allows programmers to interface with the system through libraries. Although this is not managements, more a way of interfacing.

Human Interfaces

Within computing there are two main on-screen interfaces to the computer. These are known as the CLI (Command Line Interface) and the GUI (Graphical User Interface).

CLI

The CLI was the original user interface as it was easier to implement within systems and had a low memory footprint. Because only one command can be executed at a time, and this only had text output there was very little functions to actually control the programs running, unlike the GUI which needed window management, launchers and rendering engines.

Although the command line is very basic is does not make it any less useful than a GUI. Simple commands and scripts can be run with less memory footprint than its GUI counterpart. The output from command line programs also can be “piped” into other programs, allowing one programs output to be another programs input. Within the BASH Linux Shell this link is simply made by adding a ‘|’ onto the CLI before specifying the next program.

However, as more complex tasks came along and the command set grew it became apparent that greater control was needed than that of a simple monospace text console. Computers were growing to mimic the real world better and better and as features, such as fonts, started to be used the system had to be upgraded to a graphical system, where images could be viewed, formatted text documents created and drawing tools utilised. This grew to be the beginning of the GUI interface.

GUI

The first GUI’s were very simple graphically represented icons for particular commands. Rather than typing a screen with all the options could be viewed. When the correct options were selected the command was executed, the output was processed and better graphical results could be analysed.

As GUI’s grew in popularity, with the introduction of home PC’s and novices being able to get a computer for a comparatively low price to the first the CLI became less used for tasks, even when they may have been the best to use. Microsoft Windows is the classic example of a system designed so that all could use it. Starting off with the MS-DOS (Microsoft Disk Operating System) CLI interface, its aim was to carry out simple file organising. However as its systems turned to graphical interfaces, such as its first operating systems (Windows 3.1 and Windows 3.11, released on the new 3¼” floppy disks which replaced 5½” floppy disks) the command line was not improved and by later versions (Windows 2000) it had completely disappeared from even the start up process becoming an optional component by Windows XP. The death of the command line however meant that new thinking was brought to the industry with the introduction of such specifications as CSS and HTML 4.1, designed purely for graphical viewing of the web.

The only systems that did not take on the graphical interface properly was the UNIX “headless” servers, which used a remote CLI protocol known as SHH for their operations. Windows telnet protocol, although being still active, has not got the control that the SSH protocols had.

The birth of networking

With computers coming down in price, usability becoming easier and technology to connect PC’s together operating systems had to start including tools on the average PC for network connections, and allowing users to create a home peer-to-peer network with very little configuration. Automated systems such as DHCP and DNS started to become more common, allowing systems to mask complicated operations.

Windows 3.11 for Workgroups was the first Microsoft product to allow networking. And began to have basic support for the DHCP (Dynamic Host Configuration Protocol) service, which automatically gave unique addresses to systems. As well as this it also gave support DNS (Domain Name Service), which covered up a series of numbers known as the IP with a string and letters, known as a Domain Name.

However as with all technology it can be used for bad and therefore technology to protect the technology was added, known as firewalls, which were started to be built into the Windows OS as its XP version came out. This gave significant security improvements to the first versions of Windows.

System Tools

It is important that you keep your machine both secure and well maintained. To do this you do not need expensive tools, most of them can be found legally free on the internet if you take the time to look carefully.

Disk Defragmentation

Microsoft already comes with a disk defragmenter. This tool was originally a CLI tool run with the command

This would have brought up a half-graphic interface, with blocks on your command line representing blocks on your hard disk.

The hard disk is split up into blocks which store files on your hard disk. When you start files will be stored as shown in the following diagram. The length of the block shows the size of the file.

The diagram shows a non-fragmented disk. All files follow each other without being split. This means that the computer can read the file in one block without stopping. This can speed up fetching large files significantly.

The next diagram shows a fragmented disk after “file 2” has been deleted and the bigger “file 4” has been added to the file system. The arrow shows how the system would read the file.

Because file 4 is fragmented, it is stored in two places the computer has to lookup two places on the disk before retrieving the full file. With large files this could mean that the files are stored over many different areas of the disk because there is no continuous space available for storage. A disk defragmentation puts these blocks together so that they form continuous files as shown here

A virus is a small malicious piece of code that is got from an outside source which makes your computer do an undesired operation. Viruses have various aims, from created “backdoors” for hackers, allowing them to get into an infected computer system remotely, to steeling passwords from places such as banking websites. Almost all viruses have a particular method of transferring from one PC to another, whether by automatically attaching to outgoing e-mails, sending links through instant messaging accounts or removable media, through attaching itself to another file. To save you becoming infected and to protect others it is important that you have a virus scanner installed, which is updated regularly.

One of the best free ones is AVG Free, made by Grisoft. This software can be downloaded, and new virus definitions are downloaded automatically, normally on boot. This is particularly useful as you do not have to manually make sure your software is updated.

Service Packs

Windows service packs are released for two main reasons. They first of all fix bugs which either pose a security threat to your PC or patch up features which stop working. As well as this they may install new features to your PC that allow more functionality within Windows. Service packs normally contain all the windows updates, up to the date it was released in case your PC was not updating correctly.

If you do not update your service packs you could be at risk of attack through hacking exploit frameworks, such as Metasploit and MPack, which exploit bugs in order to carry out malicious operations to your PC, depending on what “payload” the hacker sets to exploit.

Disk formatting

Can be used to ensure drive is clean before new install, and also securely erase data. A complete format will create a new File Allocation Table.

Firewall

Ensure unauthorised connections both in and out of computer are denied. Keeps computer secure.

Creating folders

Allows organisation on files into hierarchical catagories, for easy location

Backup and compression

Compression allows files to be packaged away in a smaller size before being transferred to backup media and backed up to another place, so if a problem occurs a second copy is present to allow work to continue from where left off

Bibliography