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Midterm Exam: Feb 9, 2002
Course: COSC 513 Operating Systems
Instructor: Prof. M. Anvari
Student Name: ___________________________
Student ID: ______________________
1. Enter the names for layers 1,3, and 4 of computer system, as programmers and users
view them.
4
3
1
2. How User-visible registers, and Control and status registers are used?
User-visible registers
– Enable programmer to minimize main-memory references by optimizing register use
– May be referenced by machine language
– Available to all programs - application programs and system programs
Control and status registers
– Used by processor to control operating of the processor
– Used by operating-system routines to control the execution of programs
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COSC513-Midterm Exam
February 9, 2002
Prof. M Anvari
3. What types of information are kept in User-visible registers, and Control and status
registers?
Types of registers in User-visible registers:
–Data
–Address
Index
Segment pointer
Stack pointer
Types of registers in Control and status registers
Program Counter (PC)
–Contains the address of an instruction to be fetched
Instruction Register (IR)
–Contains the instruction most recently fetched
Program Status Word (PSW)
–Condition codes
–Interrupt enable/disable
–Supervisor/user mode
4. What is Interrupt and why do the Operating Systems provide interrupt-handling
functions?
Interrupts are provided as a way to improve processing efficiency.
Handlers are responsible for managing the Interrupts.
A program that determines nature of the interrupt and performs whatever actions are needed
Control is transferred to this program
Generally part of the operating system
5. In few words define Multiprogramming, Multiprocessing, Multithreading and
Multitasking.
Multiprogramming = Multitasking.
Multiprocessing = Parallel Processing
Multithreading = Ability to support multiple threads of execution within a single process and
Not single thread of execution per process.
6. What is Cache Memory?
Small cache of expensive but very fast memory interacting with slower but much larger memor
Invisible to OS and user programs but interact with other memory management hardware
Processor first checks if word referenced to is in cache
If not found in cache, a block of memory containing the word is moved to the cache
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COSC513-Midterm Exam
February 9, 2002
Prof. M Anvari
7. What are the technological achievements of current modern operating systems?
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Processes
Memory Management
Information protection and security
Scheduling and resource management
System structure
8. What are the characteristics of current modern operation systems?
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Microkernel architecture
Multithreading
– Process is divided into threads that can run simultaneously
– Process is a collection of one or more threads
Symmetric multiprocessing
Distributed operating systems
Object-oriented design
9. How does the Operating System get executed?
 Non-process Kernel
–execute kernel outside of any process
–operating system code is executed as a separate entity that operates in privileged mode
 Execution Within User Processes
–operating system software within context of a user process
–process executes in privileged mode when executing operating system code
 Process-Based Operating System
–major kernel functions are separate processes
–Useful in multi-processor or multi-computer environment
10. What are the reasons for process terminations?
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Normal completion
Time limit exceeded
Memory unavailable
Bounds violation
Protection error
–example write to read-only file
Arithmetic error
Time overrun
–process waited longer than a specified maximum for an event
I/O failure
Invalid instruction
–happens when try to execute data
Privileged instruction
Data misuse
Operating system intervention
–such as when deadlock occurs
Parent terminates so child processes terminate
Parent request
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COSC513-Midterm Exam
February 9, 2002
Prof. M Anvari
11. What are the categories of computers with parallel processing capabilities?
12. Describe the functions of User-level thread, Kernel-level thread, and Light-weight
process. Which of the modern OS uses the LWP concept?
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COSC513-Midterm Exam
February 9, 2002
Prof. M Anvari