CSE381 Exam

A Direct Memory Access (DMA) is a hardware device that is used to

Move data from a device into main memory (RAM)

The Master Boot Record (MBR) is stored on a Hard Disk Drive (HDD) in

First sector

At startup, device drivers for an Hard Disk Drive (HDD) are typically loaded by

The OS after the kernel has already been loaded from the HDD

On modern CPUs, the OS-kernel(s) typically run in a privileged mode called

Ring 0

In a modern quad-core, dual-CPU server the number of OS-kernels(s) running on the server would be

1

The virtua memory subsystem of an OS also manages

The main memory (RAM)

In a 32-bit microprocessor, the virtual memory for a process is limited to 4 GB. Consequently the total virtual memory that the OS can access and manage is limited to

Amount of space reserved for virtual memory on secondary storage

The first system call that is typically reported for a program by strace is

Execve

The process ID (PID) for the first init process started by Linus is

1

The most concise definition of a mutable pointer (pointer can be changed to point elsewhere) to a constant integer value would be

cont int\* ip;

The result of the expression 5 + 3 \* 2 is

11

The value stored in the variable result due to the following C/C++ language statement (same behavior in Java too) would be:

\
int result = 3 % -2;

1

Which one of the following is a valid and a real infinite loop?

for (;;);

Which one of the following is not a functionality of a conventional operating system

Manage caches on a CPU

The minimum number of cores and CPUs that are required to run a multi-tasking operating system like Linux is

One CPU with 1 core

A computer with 1 GB of RAM is synonymous to a computer with

1024 MB of RAM

The fastest storage device on a conventional CPU are

Registers

The expansion of RAM is

Random Access Memory

An application what would significantly benefit by running in batch processing mode would be

A simple program to multiply several large matrices

The most suitable operating system for gaming consoles that run one game for a player wuold be

Multi-tasking operating system

The minimum number of threads that are present in a standard process created by modern operating systems would be

1

Assume a process consists of 3 threads, namely T1, T2, and T3 and the threads were started in the order T1, T2, and T3. The order in which the 3 threads will join is:

The order in which threads will join is not deterministic

Which one of the following resources is not shared by default between multiple threads

Program stack

Given an 8 core CPU the maximum number of threads that can be created in one single process is

Depends on the maximum threads supported by OS

A good example of a Task Parallel application would be

Converting a vide to MPEG4/H264, OGV, and MOV format

A good example of a Data Parallel application would be

Converting each pixel in a photo to black-n-white

The number of monitors that are necessary to ensure MT-safe access to the SharedValue shown in the code fragment below would be:

0

Suitable command (or command-chain) to list just the processes associated with your login-id

ps -fea | grep raodm

Which one of the following resource is not managed by the operating system

Caches on the CPU

The minimum number of cores and CPUs that are required to run a multi-tasking operating system like Linux is

One CPU with 1 core

The expansion for BIOS is

Basic Input Output System

An application that would significantly benefit by running in batch processing mode would be

A program to compute the billionth digit of the irrational constant pi

The most suitable operating system for a smart phone would be

Multi-processing operating system

A suitable operating system design for a micro System on a Chip (SoC) device is

Monolithic design

The BIOS Parameter Block (BPB) for a FAT-12 file system is stored on disk in the

The Master Boot Record in the middle of the boot loader code

The smallest unit of data that can be physically read from spinning storage media is

A sector

The first process that is started by the Linux operating system is called

Init

In Linux, when a program is run as a background process, it

It runs normally, but cannot read input from the terminal

The -Wall option to the GNU compilers (gcc/g++) is used to

Generate warnings that are potential sources of errors in the program

In OS terminology, “device drivers” are

Software used to interface OS to hardware

What is the expansion of the acronym API?

Application Program Interface

Environment and energy are the greatest challenges facing humanity. Given that nearly 25% of the global energy (by some estimates) is consumed by technology, it is imperative that we try to use the most energy and resource-efficient programming language. Which one of the following programming languages is the most energy-efficient?

C++

Which one of the following is not a system?

A data communication network

The primary motivation for systems programming is to

Develop software such as operating systems, web-servers, etc

In the following debugger button in VS-Code, clicking button 1 causes the debugger to:

Continue running until next breakpoint

In the following debugger buttons in VS-Code, clicking button 4 causes the debugger to:

Run until end of the method

In the following debugger buttons in VS-Code, the button to step over to the next line of code is

2

The following for-loop that iterates over a string works:

\
std::string str = "some data";

for (int i = 0; (i < str.size()); i++) {

str\[i\] = '\*';

}

\
However, the compiler generates a warning:

warning: comparison between signed and unsigned integer expressions

\
The correct solution to fix this issue would be

Change int to size_t

std::string str = "123456789";

std::string **s** = str.substr(2, 3);

345

Assume the following code is used to read user inputs.

int i;

std::string str;

std::cin >> i >> i >> str;

Assume the user enters the following input. The data that will be stored in the variable str will be:

10 20 testing

testing

Assume the following code is used to read user inputs.

std::string str;

std::cin >> std::quoted(str);

Assume the user enters the following input. The data that will be stored in the variable str will be:

this is a test

This

Given the following code fragment,

int main(int argc, char \*argv\[\]) { std::cout << argv\[0\] << std::endl; }

The value in argv\[0\] will be:

Path to the executable file name

The correct/preferred signature for a function named doIt, that accepts a string that the function is not going to modify, would be:

void doIt(const std::string& str)

Assume the following code

void doIt(std::string s);

The method is using:

Pass by value

Assume user inputs 3 numbers, each separated by a blank space (*e.g.*, "123 45 8345" or "8345 123 45", etc.). The input is stored in a string object named str. The __simplest way__ to read the 2nd integer from the string str into the integer i would be to:

std::istringstream is(str);

is >> i >> i;

In order to write/overwrite data to a file, the correct stream to use is

std::ofstream

Given the following code fragment, the 2nd line of code that access an entry:

std::unordered_map

Adds an entry with key/index "test" with value 22

Given the following definition for an unordered_map, what is the preferred approach for inserting/adding a value into the unordered_map?

using StrIntMap = std::unordered_map

wordNum\["three"\] = 10;

The preferred method to add an element to the end of a vector is

push_back

The correct approach/syntax to insert an element x at the ith index position in a vector vec is

vec.insert(std::begin(vec) + i, x);

The correct approach/syntax to delete/remove an element x at the ith index position in an vector vec is

vec.erase(std::begin(vec) + i);

Given two strings str1 and str2, the correct/preferred way to check to see if the two strings are equal (*i.e.*, have exactly the same sequence of characters) is:

str1 == str2

The value stored in variable s shown below is (Note: sub-string in C++ has different parameters than Java)

std::string str = "123456789";

std::string **s** = str.substr(7);

89

Assume the following code

void doIt(int& i);

The method is using:

Pass by reference

The correct approach/method to check if a given value exists in an unordered_map is to use

Use find() method

In a multiprocessing OS, the process of permitting a different process to use the CPU is called

Context switching

What is the expansion of the acronym GNU

GNU’s Not Unix

The page tables in a TLB are switched by an OS as part of

Context switching

What does the term PPID stand for?

Parent Process Identifier

In GNU/Linux users are organized into groups. A key capability enabled by the use of groups is

Ease sharing files between users

In GNU/Linux, system configuration files are typically stored in

/etc

The fastest storage on a computer are

CPU Registers

What is the expansion of the acronym CPU?

Central Processing Unit

The Translation Lookaside Buffer (TLB) is used to

Map virtual addresses to real addresses

The uid of root is

0

In GNU/Linus what is uid?

A unique number associated with each user

A syscall is

Function call to the OS

The last system call that a process always makes in called

exit_group

A key reason why system calls are a bit slower is because

Switching to privileged ring takes time

What is POSIX?

Standard set of APIs an OS must support

The first stage boot loader of an OS is loaded by

BIOS

What is the expansion of the acronym BIOS?

Basic Input Output System

What is the commonly used boot loaded for Linus called?

grub

The line of code that may experience a Running → Ready transition would be

Line number 4

Given the process tree below, the command kill -9 137 will kill processes

137, 127, and 147

The line of code that would cause a Running → Waiting transition would be

Line number 6

Assume you are running a simple console program via the Linux terminal. An easy way to abort the program would be to

Control+C

A malicious program (aka virus) is running on a computer consuming resources. In which type of multitasking would the user experience the most inconvenience?

Non-preemptive multitasking

XBox and PS4 are designed to run resource-intensive games. They run one game at a time so that the game can monopolize resources like CPU time, memory, GPU, etc. A good multitasking approach for such application is

Non-preemptive multitasking

Which of the following sequence of fork system calls correctly create the process hierarchy shown below. Assume the code starts running in the process at the root of the hierarchy:

if (fork() == 0) {

if (fork() == 0) {

fork(); } }

The return value of the fork (system call) is

Zero in the child process

The exit code of a program is interpreted as

Zero indicates success and non-zero indicates errors

Which of the following sequence of fork system calls correctly create the process hierarchy shown below. Assume the code starts running in the process at the root of the hierarchy:

fork();

fork();

The exit code of a program is

Return value from main function

Assume the following method is being run by a process. Excluding this parent process (i.e., the process that is initially running the method below), the total number of child processes created would be:

void forkyMon() {

if (fork() > 0) {

fork(); } }

2

First study the following code fragment that creates 2 file streams:

std::ofstream log("log.txt");

int pid = fork();

std::ifstream info("input_data.txt");

Given the above code fragment, which of the following applies to the log stream?

The log stream is shared by both parent and child processes

Given the following line of code below, which of the following statements is true:

auto pid = fork();

The virtual memory address of pid is the same in the parent and child

After successfully starting the specified program the execvp command

Never returns to the calling process

The exit code of a child process is

The return value from the main function of the child proess

Assume the forkNexec method below is a helper method that – runs a given program in a child process while returning PID of the child in the parent process. What would be the estimated runtime of the sleepy method?

// Helper method \n int forkNexec(std::vector argList); \n \n void sleepy() {

int pid1 = forkNexec({"sleep", "3"}); \n int pid2 = forkNexec({"sleep", "2"});

waitpid(pid1, nullptr, 0); \n waitpid(pid2, nullptr, 0); }

3 seconds