Student Book Pages 170-173
What is an operating system?
Nowadays, the majority of electronic devices have specific software that servers as an intermediary between the physical electronics, known as hardware, and the rest of the program and applications. This is the known as the operating system.
An operating system is the central software that allows all of the system´s resources to be used and administered correctly.
In the folllowinf block diagram,showing both hardware and software, the opeating system is placed between them, as you can seein the figure:
The operating system connects the hardware (bottom) to the user programs and applications (top). Both ends, hardware and applications, are controlled by a layered system, which makes up the operating system. The essential element of the operating system is the kernel. The kernel is the core of the operating system and it has three main functions:
- Control the data-flow processes.
- Provide the operational capacity in order for peripherals and devices to function. To do so, the operating system has software containing the controllers, or drivers, which ‘translate’ the operating system’s data into actions that make the peripherals function (screen, CD unit, keyboard, USB port, etc.).
- Administer main memory. The operating system receives a high number of requests for different programs to work, and it establishes priorities that distribute a portion of the main memory to each application and program that is running.
Above the kernel is the system call block. This operating system block acts as a link between the kernel and the upper layers. When the user, or programs or application, requests a service from the operating system, the system call is in charge of choosing the right process to activate the necessary resources and execute the right actions in the kernel.
Some of the requests from the system call involve gaining access to the peripherals when writing or reading data from external units, obtaining the date and time, gaining access to a file’s content, and so on. Posix is a specific family of system calls containing a set of common calls frequently used in operating systems.
Above the system call is a double layer consisting of the Shell, which is the command interpreter, on the kernel’s side, and the Graphical User Interface (GUI) on the user’s side.
When a user interacts with a computer, moving the cursor over the screen with the mouse or typing with the keyboard, they can see these actions on the screen thanks to the GUI. At the same time, they are asking the Shell to interpret these actions and launch a series of instructions to be executed by the kernel. This double layer serves as a translator between the user and the system itself.
Uses of operating systems
The operating system is the first software to be loaded in the main memory when a computer, or any computer device, is turned on. Once it is loaded, the software and computer operation is controlled by the operating system, which responds to the commands of the user.
However, could a system operate without an operating system? Why is the operating system necessary? In answering this question you will have to mention the operating system’s functions.
The majority of the software that controls the hardware consists of routines, or in other words, small programs that always function following the same actions. The operating system automates these routines and saves the user the trouble of having to do so.
Furthermore, computers use many resources and the operating system is able to make the best use of the computer by enabling them to function together. In this way, peripheral devices, as well as the system’s resources and main memory, are used more efficiently.
Lastly, there are many reasons why the operating system is a central software element, one of which is the security that it provides by controlling access and use of the computer’s resources. This is especially important when the computer is used by several users.
The evolution of operating systems
Before operating systems, any execution in the computer system was done by the machine operator. It was a tedious task because it required the person in charge of the system to dedicate their time to changing the connections of the peripherals and executing the programs every time a new task needed to be done. Therefore, in the 1950s, programs were created that automated these tasks by joining together various executions, which was known as batch processing. The operator’s task was reduced since it was now the machine that automatically linked one program to another.
Over time, these types of programs began to be known as resident monitor programs and they constitute the basis for current operating systems.
A major step forward in computing was made in the 1960s when computers were able to process other programs whilst the program running was inactive, waiting for a data operation in the input and output peripherals to finish.
This was the basis for multiprogramming, which is the capacity of a system to execute different programs at the same time. In order to do so, it is necessary for the operating system be able to control multiple processes. The next step was to achieve faster processing speeds by reducing the response time.
In 1981, the company IBM innovated computer systems by introducing the personal computer, or PC, which came equipped with an operating system made specifically for this small computer’s capacity. In this model, the operating system was the central element that monitored all of the computer’s resources, becoming a precursor to current operating systems. The only difference was that the operating system had to be loaded from an external disk every time the PC was used. This operating system was called IBM PC DOS (personal computer disk operating system).
The success of the PC resulted in computers being equipped with a permanent secondary memory, the hard drive, in which the operating system would be stored. Every time the computer started up, the operating system automatically loaded in the main memory.
At that time, operating systems communicated with the user through a command-line interface, known as textbased operating systems.
The user interacted with the computer by typing commands and parameters. Nowadays, operating systems have this interface as just another utility.
At the end of the 1980s and the beginning of the 1990s, increased computer speed and capacity paved the way for graphical user interface (GUI) operating systems, which allowed information to be shown and programs to be executed by graphic elements and icons.
Over time, we have seen the need to connect computers to networks and organise the distributed operating systems. Doing so allows a user that is connected to a network to access all the resources it provides, such as shared printers, shared permanent disk space, and so on. This allows a larger system to be created by adding the resources of all the connected computers.
All of the integrated resources from various computers are known as the virtual machine.
Comparing operating systems
The main operating systems in terms of number of licenses are Microsoft Windows, Apple Macintosh and the Linux operating systems. Each one has its advantages and disadvantages, but when choosing one over another, check its characteristics in the following table:
