PURDUE CS 354 - MIDTERM STUDY
GUIDE EXAM QUESTIONS AND
ANSWERS GRADED A+ 2026
Why do we use XINU? - ANS It is small, complete, elegant, powerful, and practical. We can
also run it on real hardware, which gets rid of any work done by VM.
What is an operating system? - ANS It provides an abstract computing environment, supplies
services, manages resources, hides low-level hardware.
What are some services an OS provides? - ANS Support for concurrent execution, process
synchronization, inter-process communication, file system, etc.
How are OS services accessible to users? - ANS Each OS service is accessed through a system
call interface. Inside these system calls is where the internals of the call are done. Normally a
library wraps these system calls.
What is the open-close-read-write paradigm? - ANS Application uses open to connect with
file, then calls functions to read or write data, then calls close to terminate use.
What are the two ways to achieve concurrent processing? - ANS Real concurrency achieved
by hardware (physical components operate concurrently, CPU/IO work together).
Apparent Concurrency achieved by multitasking (multiple programs appear to operate
simultaneously, but the OS provides this illusion).
@COPYRIGHT 2026/2027 ALLRIGHTS RESERVED 1
, What is a process? - ANS It is an active computation (i.e. the execution or running of a
program). It is an OS abstraction created by a system call, managed entirely by the OS.
Note: "Processes" in XINU are more like threads, they share the same address space but have
their own stack.
What is the consequence for programmers? (Process storage) - ANS A copy of function
arguments and local variables are associated with each process executing a particular function,
not with the code in which they are declared.
What are the major OS components? - ANS Process manager, memory manager, device
manager, clock manager, file manager, interprocess communication, intermachine
communication, assessment
What is a multilayer structure? Does XINU use it? - ANS It is visible to user and designer, each
layer is used by layer directly above, provides protection as well as data abstraction, but it can
be inefficient (Ex: Internet Protocol). No, XINU does not use it.
What is a multilevel structure? Does XINU use it? - ANS It is a form of data abstraction, which
is used during system construction. It allows designers to focus on one thing at a time, and
allows given level to use *all* lower levels. This is quite efficient, and used by XINU.
How to build an OS? - ANS Begin with philosophy, establish policies, design mechanisms, and
construct an implementation.
Ex:
Philosophy: "Fairness"
Policy: FCFS
Mechanism: Queue of requests (FIFO)
Implementation: C program.
@COPYRIGHT 2026/2027 ALLRIGHTS RESERVED 2
GUIDE EXAM QUESTIONS AND
ANSWERS GRADED A+ 2026
Why do we use XINU? - ANS It is small, complete, elegant, powerful, and practical. We can
also run it on real hardware, which gets rid of any work done by VM.
What is an operating system? - ANS It provides an abstract computing environment, supplies
services, manages resources, hides low-level hardware.
What are some services an OS provides? - ANS Support for concurrent execution, process
synchronization, inter-process communication, file system, etc.
How are OS services accessible to users? - ANS Each OS service is accessed through a system
call interface. Inside these system calls is where the internals of the call are done. Normally a
library wraps these system calls.
What is the open-close-read-write paradigm? - ANS Application uses open to connect with
file, then calls functions to read or write data, then calls close to terminate use.
What are the two ways to achieve concurrent processing? - ANS Real concurrency achieved
by hardware (physical components operate concurrently, CPU/IO work together).
Apparent Concurrency achieved by multitasking (multiple programs appear to operate
simultaneously, but the OS provides this illusion).
@COPYRIGHT 2026/2027 ALLRIGHTS RESERVED 1
, What is a process? - ANS It is an active computation (i.e. the execution or running of a
program). It is an OS abstraction created by a system call, managed entirely by the OS.
Note: "Processes" in XINU are more like threads, they share the same address space but have
their own stack.
What is the consequence for programmers? (Process storage) - ANS A copy of function
arguments and local variables are associated with each process executing a particular function,
not with the code in which they are declared.
What are the major OS components? - ANS Process manager, memory manager, device
manager, clock manager, file manager, interprocess communication, intermachine
communication, assessment
What is a multilayer structure? Does XINU use it? - ANS It is visible to user and designer, each
layer is used by layer directly above, provides protection as well as data abstraction, but it can
be inefficient (Ex: Internet Protocol). No, XINU does not use it.
What is a multilevel structure? Does XINU use it? - ANS It is a form of data abstraction, which
is used during system construction. It allows designers to focus on one thing at a time, and
allows given level to use *all* lower levels. This is quite efficient, and used by XINU.
How to build an OS? - ANS Begin with philosophy, establish policies, design mechanisms, and
construct an implementation.
Ex:
Philosophy: "Fairness"
Policy: FCFS
Mechanism: Queue of requests (FIFO)
Implementation: C program.
@COPYRIGHT 2026/2027 ALLRIGHTS RESERVED 2
