COMP 362 Study Set 2

List the categories of system programs that you know and described what they are used for.

Mac OS, MS DOS ,etc. System programs make it easier for users to use the computer and also it has a certain amount of protection in case if a program attempts to edit something that is important.

List common types of system calls and describe what they are used for.

Process control: end(abort), load/execute, create process/terminate process, get attributes/set process attributes, wait for time, wait event/signal event, allocate and free memory. File management: create file/delete file, open/close, read/write/reposition, getfile attributes/setfile attributes. device management: request device/ release device, read/write/reposition, get device attributes/set device attributes, logically attach or detach devices. Information Maintenance: get time or date/set time or date, get system data/set system data, get process/file/or devoce attributes, set process/file/or device attributes. Communications: create/delete communication connection, send/receive messages, transfer status info, attach or detach remote devices.

List and describe OS services for resource sharing.

Resource Allocation: When multiple users or multiple jobs run concurrently, resources must be allocated to each of them Accounting: To keep track of which users use how much and what kinds of computer resources Protection and Security: The owners of information stored in a multiuser or networked computer system may want to control use of that information, concurrent processes should not interfere with each other

What is a system call? What is it used for? How can it be implemented? Do application programs usually use system calls directly?

System Call: Provide an interface to the services made available by an operating system. It can be used to store data and also make changes that only the kernal can do. One approach is for the program to ask the user for the names. In an interactive system, first to write a prompting message on the screen then to read from the keyboard the characters that define the two files. Yes application programs do take advantage of system calls directly. In an API, the system execytes thousands of system calls per second.

Describe the following aspects of microkernel approach to system design: the main advantages this approach to system design, the disadvantages, the pragmatic approaches that employ the microkernel ideas, but limit the deficiencies of pure microkernel-based architectures?

The main advantages this approach to system design Communication takes place between user modules using message passing,easier to extend a microkernel, easier to extend a microkernel, easier to port the operating system to new architectures, more reliable, more secure. Disadvantages: Performance overhead of user space to kernel space communication.

What is the purpose of the command interpreter (shell)? Why is a shell usually separate from the kernel?

The main function of the command interpreter is to get and execute the next user-specified command. Many of the commands given at this level manipulate files. The shell is usually separate from the kernel because the kernel is the one that controls the communication between the hardware and the software. The shell only interprets what the machine code and makes it easier for us to understand.

What is the purpose of system programs (utilities)? Why are they a better solution than providing system or shell built-in functions.

The purpose if system programs (utilities) is to provide a convenient environment for program development and execution. They are a better solution because they provide flexibility in available utilities rather than being tied to what is available as built-in functions.

How can parameters be passed to system calls?

Three general methods are usd to pass parameers to the operating system. 1. They are pushed or placed onto the stack. 2. Pass the parameters in registers. 3. Parameters stored in a block, or table, in memory, and address of block passed as a parameter in a register.

Explain what a bootstrap program and an Operating System loader are, and what's the difference between them.

Before any OS can be loaded and started, the computer needs to go through a boot strapping process. After power-up self-tests, the code that is called bootstral loader tests and initializes the hardware and then loads the computer's operating system. The OS loader will allow users to select from a number of OSes. The difference is the Operating system loader is only the OS, while the bootstrap is a checker in case the computer's hardware is faulty.

List the services provided by an operating system to users. Explain how each provides convenience to the users. Explain also why user-level programs cannot or should not provide these services.

1. User Interface: A user interface makes it easier for users to navigate around. In a command-line interface, they have a set of instructions which the user can enter to get to where they want. While a graphical user interface allows users to visually see what is going on. 2. Program execution: The system must be able to load a program into memory and to run that program. This is a convenience to users because they would be able to create their own programs. 3. I/O operations: A running program may require I/O, which may involve a file or an I/O device. This is a convenience to users because they are able to store information on CDs or any type of external drives. 4. File-system maniplation: The file system is of particular interest. Obviously, programs need to read and write files and directories, create and delete them, search them, list file Information, permission management. 5.Communication: Processes may exchange information, on the same computer or between computers over a network 6.Error Detection: OS needs to be constantly aware of possible errors • May occur in the CPU and memory hardware, in I/O devices, in user program • For each type of error, OS should take the appropriate action to ensure correct and consistent computing • Debugging facilities can greatly enhance the user's and programmer's abilities to efficiently use the system