OS theory concept map

Section 1:

Regarding operating systems, there are several functions included. An operating is made up of a user interface, program execution, I/O operations, file system manipulation, communication, and error detection. These functions are user-based. System based functions include resource allocation, accounting, as well as security and protection (Silberschatz, A., Galvin, P. B., & Gagne, G. 2014).

The user interface includes one or more functions, which include command line, GUI, or batch, to call commands to the operating system. Program execution allows the operating system to start, run, and execute programs. I/O operations allow the system to operate devices such as a printer. File system manipulation allows for files to be written and read. Communication allows the operating system to communicate among the different functions. Error detection detects and corrects errors within the system, such as a file error or I/O error (Silberschatz, A., Galvin, P. B., & Gagne, G. 2014).

Resource allocation allows the operating system to divide up resources to multiple users that may be using the system. This function allocates memory space, disk space, or file space. Accounting is another system function that keeps track of the resources that are being used by different users. The final function is protection and security, which controls and protects access to the system resources from outside users (Silberschatz, A., Galvin, P. B., & Gagne, G. 2014).

Figure 1. Operating system functions

Section 2:

One significant aspect of an operating system is known as a process. A process is defined as a program in execution (Silberschatz, A., Galvin, P. B., & Gagne, G. 2014). An example of a process would be the word application that is being used to type this assignment. Another process might be the web browser that is up as I reference information from the course textbook. When describing processes, we also need to discuss the process state. According to the textbook, as processes execute, the state the process is in will change. The process may be either new, running, waiting, ready, or terminated. These include the creation of the project through completion. (Silberschatz, A., Galvin, P. B., & Gagne, G. 2014). A process control block includes information that is associated with each process. The PCB includes process state, process counter, CPU registers, and scheduling information, memory, accounting, and I/O status information (Silberschatz, A., Galvin, P. B., & Gagne, G. 2014).

Regarding threads, there are two different options, which include single-threaded and multi-threaded processes. A single thread is defined as a single unit of CPU use which can perform one task at a time whereas a multi-thread can perform multiple tasks (Silberschatz, A., Galvin, P. B., & Gagne, G. 2014). An example of a multi-thread may be a word processor that can display text as it is typed while also spell checking. One point to consider when discussing processes is the critical section problem. When a process is in its critical section, no other processes can also be in its critical section. If one process is in its critical section, other processes must wait to enter the critical section. (Silberschatz, A., Galvin, P. B., & Gagne, G. 2014). A real-life example of this may be a drive-through car wash. If one car is in the car-wash, other cars must wait to enter. Once the car wash is complete, the next car may enter.

Figure 2. Operating system processes.

Section 3:

Regarding memory and memory management, most would agree memory is one of the most important aspects of a computer system. Memory management is the functionality where an operating system moves processes back and forth from the main memory to disk memory for the processes to execute (Tutorial point, N.D.). Some memory management functions include address binding where a program is moved from storage to become a process at some point during the compile, load, or execution times. Dynamic loading keeps certain routines that are part of a program on disk memory to utilize more memory space. Swapping includes processes that are swapped in and out of memory to a backing store, which allows for more multi programming. Memory allocation involves memory that is divided into two partitions.  These two partitions include low memory for the operating system and high memory for the user processes (Tutorial point, N.D.).

Addresses that are generated by the CPU are known as logical or virtual addresses, whereas addresses seen by the memory unit are known as physical addresses. Logical address space is the total set of all logical addresses, whereas physical address space is the complete set of physical addresses. According to the text, execution times can differ between logical and physical address space. Logical addresses must be mapped to physical addresses before they can be used, and this is done with the memory management unit (Silberschatz, A., Galvin, P. B., & Gagne, G. 2014).

Figure 3. Operating system memory management

Section 4:

When discussing files and file management, we can define this as software that manages data files in a computer system (Silberschatz, A., Galvin, P. B., & Gagne, G. 2014). The system organizes the data files to allow easy access. Attributes of a file include name, identifier, type, location, and protection (Tutorial point, n.d.). The operations of file management include creating the file where the file is created in the directory. Reading the file consists of a read pointer that specifies where the file should be read. Writing a file includes a system call that specifies the file name and what needs to be written. Deleting a file locates the file and removes it. Repositioning a file includes setting a file value to the appropriate entry. The last operation is truncating, where data from the file is deleted without destroying all file attributes (Silberschatz, A., Galvin, P. B., & Gagne, G. 2014).

File management includes various structures which include such as single level, two-level, tree-structure, acyclic, and graph directories. Single-level directories are directories where all files are contained in the same directory. Two-level directories allow each user to utilize their own file directory. Tree structure directories enable users to create their own sub-directories to organize files. Acyclic graph directories share sub-directories and files. General graph directories are similar to tree structure directories, but in general graphs, links are added, and cycles can occur, which dismantles the tree structure (Silberschatz, A., Galvin, P. B., & Gagne, G. 2014).

Figure 4. Single-level directory

Figure 5  Two-level directory

Figure 6. Tree-structured directory

Figure 7. Acyclic-graph directory

Figure 8. General graph directory

Regarding input and output devices, there are various options available. The devices are divided between hardware and software. Some hardware input devices include mouse and keyboards, whereas output hardware includes monitors, audio, and printers. Input and output software consist of the device drivers that communicate with the devices, allowing them to operate. Device drivers are connected to the operating system and help control the I/O device. The device controller works as an interface between the device and the device driver and includes electrical components (Tutorial point. n.d.).

 Section 5:

When discussing protection and security, we can differentiate the two be describing protection as internal and security external. Within protection, we have domain-based and language-based. According to the text, domain-based protection gives access rights that determine how a process operates (Silberschatz, Galvin, & Gagne, 2014). A way we can illustrate how this works is by looking at an access matrix. An access matrix is a table where the rows are individual domains, and the columns are objects.

The table will show which domain has rights on each object. For example, domain one might only be allowed to read objects two and four, whereas domain three might be able to read and write on objects one and three (Silberschatz, Galvin, & Gagne, 2014). Language-based protection involves programming languages. These programming languages include high-level policies that are referenced when attempting to allocate resources. User-defined system functions, as well as access to files, are also protected by these programming languages. (Silberschatz, Galvin, & Gagne, 2014).

As mentioned before, security is an external aspect. Security protects a system from external threats. Some of these threats or attacks include Trojan viruses, trap doors, logic bombs, or stack and buffer overflow. These threats and attacks are mitigated by several security features such as antivirus software, cryptography, authentication, encryption, and firewalls (Silberschatz, Galvin, & Gagne, 2014). These types of security options can be used in tandem with one another to secure a system further.

Figure 9. Protection vs. security

Summary:

The operating system is one of the most important parts of a computer system. By definition, a computers operating system includes system software that manages  computer hardware, software resources, and provides common services for computer programs (Silberschatz, A., Galvin, P. B., & Gagne, G. 2014). Throughout this course we have discussed many different aspects within an operating system such as OS functions, processes, memory management File systems, Mass storage, I/O, as well as Security and protection. We will discuss a few points regarding these features.

An operating system includes user interface such as a GUI, program execution, I/O operations, file system manipulation, communication, and error detection. These functions are user-based. System based functions include resource allocation, accounting, as well as security and protection (Silberschatz, A., Galvin, P. B., & Gagne, G. 2014). Program execution allows the operating system to start, run, and execute programs. I/O operations allow the system to operate devices such as a printer. File system manipulation allows for files to be written and read. Communication allows the operating system to communicate among the different functions. Error detection detects and corrects errors within the system, such as a file error or I/O error (Silberschatz, A., Galvin, P. B., & Gagne, G. 2014).

Figure 10. OS user functions

Within a computer, we have many processes that execute. A process is the instance of a computer program that is being executed by one or many threads. ... Depending on the operating system, a process may be made up of multiple threads of execution that execute instructions concurrently (Silberschatz, A., Galvin, P. B., & Gagne, G. 2014). Simply put, a process is a program in execution.  as processes execute, the state the process is in will change. The process may be either new, running, waiting, ready, or terminated. A process control block includes information that is associated with each process. The PCB includes process state, process counter, CPU registers, and scheduling information, memory, accounting, and I/O status information (Silberschatz, A., Galvin, P. B., & Gagne, G. 2014).

Figure 11. Single threaded process

Memory management is the functionality where an operating system moves processes back and forth from the main memory to disk memory for the processes to execute (Tutorial point, N.D.). Some memory management functions include address binding where a program is moved from storage to become a process at some point during the compile, load, or execution times. Dynamic loading keeps certain routines that are part of a program on disk memory to utilize more memory space. Swapping includes processes that are swapped in and out of memory to a backing store, which allows for more multi programming. Memory allocation involves memory that is divided into two partitions.  These two partitions include low memory for the operating system and high memory for the user processes (Tutorial point, N.D.).

Figure 12. Process swapping

File management includes actions where the system organizes the data files to allow easy access. Attributes of a file include name, identifier, type, location, and protection (Tutorial point, n.d.). The operations of file management include creating the file where the file is created in the directory. Reading the file consists of a read pointer that specifies where the file should be read. Writing a file includes a system call that specifies the file name and what needs to be written. Deleting a file locates the file and removes it. Repositioning a file includes setting a file value to the appropriate entry. The last operation is truncating, where data from the file is deleted without destroying all file attributes (Silberschatz, A., Galvin, P. B., & Gagne, G. 2014).

File management includes various structures which include such as single level, two-level, tree-structure, acyclic, and graph directories. Single-level directories are directories where all files are contained in the same directory. Two-level directories allow each user to utilize their own file directory. Tree structure directories enable users to create their own sub-directories to organize files. Acyclic graph directories share sub-directories and files. General graph directories are similar to tree structure directories, but in general graphs, links are added, and cycles can occur, which dismantles the tree structure (Silberschatz, A., Galvin, P. B., & Gagne, G. 2014). Mass storage may be handles by a hard disk drive or an external device such as a hard drive. I/O operations such as printing are handled by device controllers and drivers.

Figure 13. User within double level directory

Two mechanisms used to control access to a computers programs and resources is protection and security. Protection can be thought of as an internal mechanism where as security is external. Within protection, we have domain-based and language-based. According to the text, domain-based protection gives access rights that determine how a process operates (Silberschatz, Galvin, & Gagne, 2014). A way we can illustrate how this works is by looking at an access matrix. An access matrix is a table where the rows are individual domains, and the columns are objects.

Figure 14. Access control matrix

Security protects a system from external threats. Some of these threats or attacks include Trojan viruses, trap doors, logic bombs, or stack and buffer overflow. These threats and attacks are mitigated by several security features such as antivirus software, cryptography, authentication, encryption, and firewalls (Silberschatz, Galvin, & Gagne, 2014).

Given everything learned throughout this course, I feel as if I will benefit greatly. Regarding my career, I currently work for Comcast business. I work on a computer system everyday and having the knowledge behind the operating system is great knowledge to have. Furthermore, I am planning to transition into a position in information technology upon completion of my degree at Ashford university. I recently participated in a job shadow with the I.T. department at Comcast and was exposed to many of the departments job functions which included general repair and maintenance of company issues laptops. These repairs included deep dive into the systems operating systems. The information covered in this course allowed me the ability to understand what the I.T. techs were doing as they worked on these systems.

References

File System Management. (n.d.). Retrieved from https://www.tutorialspoint.com/File-System-Management (Links to an external site.)

Operating system – Services (Links to an external site.). (n.d.). Retrieved from https://www.tutorialspoint.com/operating_system/os_services.htm

Operating Systems-Memory Management. (n.d.). Tutorial Point. Retrieved from https://www.tutorialspoint.com/operating_system/os_memory_management.htmLinks to an external site.

Operating system – I/O hardware (Links to an external site.) (Links to an external site.). (n.d.) Retrieved from https://www.tutorialspoint.com/operating_system/os_io_hardware.htm

Operating system – I/O softwares (Links to an external site.) (Links to an external site.). (n.d.). Retrieved from https://www.tutorialspoint.com/operating_system/os_io_software.htm

Silberschatz, A., Galvin, P. B., & Gagne, G. (2014). Operating system concepts essentials (2nd ed.). Retrieved from https://redshelf.com/