CS372: Homework 4

Problem 1:

Which of the following components is responsible for loading the initial value in the program counter for an application program before it starts running:

        * Compiler
        * Linker
        * Loader
        * Boot module or boot ROM

Problem 2:

Given the following program that uses three memory segments in an address space as described in class (code segment, data segment ,and stack segment):

char a[100];
main(int argc, char ** argv)
{
    int d;
    staticdouble b;
    char *s = "boo", * p;

p = malloc(300);
return 0;
}

Identify the segment in which each variable resides and indicate if the variable is private to the thread or is shared among threads.
Be careful.

Problem 3

A hardware designer argues that there are enough transistors on the chip to provide 1024 integer registers and 512 floating point registers. You have been invited as the operating system guru to give opinion about the new design.

        1. What is the effect of having such a large number of registers on the operating system?
        2. What additional hardware features you would recommend added to the design above.
        3. What happens if the hardware designer also wants to add a 16-station pipeline into the CPU. How would that affect the context
            switching overhead?

Problem 4

Given the following piece of code:

main(int argc, char ** argv)

{

int child = fork();

int c = 5;

if(child == 0)
{

c += 5;

}

else

{

child = fork();

c += 10;

if(child)

c += 5;

}

How many different copies of the variable c are there? What are their values?

Problem 5

Given the following piece of code

main(int argc, char ** argv)

{

forkthem(5)

}

void forkthem(int n)

{

if(n > 0)

{

fork();

forkthem(n-1);

}

How many processes are created if the above piece of code is run? Hint: It may be easier to solve this problem by induction.

Problem 6

What is the output of the following programs (inspect the manual for the system calls if you need more information, but please solve the problem without compiling and running the program).

Program 1:
main()
{
    val = 5;
    if(fork())
        wait(&val);
    val++;
    printf("%d\n", val);
    return val;
}

Program 2:
main()
{
    val = 5;
    if(fork())
        wait(&val);
    else
        exit(val);
    val++;
    printf("%d\n", val);
    return val;
}