SampleMidterm - ECE-C490 Introduction to Operating Systems...

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ECE-C490: Introduction to Operating Systems Midterm Exam (Winter 2008 - 2009) February 9, 2009 The exam is closed book and comprises of 5 questions. 1. (10 points) Consider the following snippets of code. int main(int argc, char **argv) { int a = 10; int v = 0; v = fork(); if (v < 0) exit(-1); if (v == 0) { /* Child code */ a = a + 5; printf(”Value of a is %d \n” , a); /* LINE A */ exit(0); } /* Parent code */ wait(NULL); a = a - 5; printf(”Value of v is %d \n” , v); /* LINE B */ printf(”Value of a is %d \n” , a); /* LINE C */ exit(0); } int main(int argc, char **argv) { int a = 10; int v = 0; v = vfork(); if (v < 0) exit(-1); if (v == 0) { /* Child code */ a = a + 5; printf(”Value of a is %d \n” , a); /* LINE A */ exit(0); } /* Parent code */ wait(NULL); a = a - 5; printf(”Value of v is %d \n” , v); /* LINE B */ printf(”Value of a is %d \n” , a); /* LINE C */ exit(0); } (a) (b) Assume that the process ID of the parent process maintained by the kernel is 9500, and that no new processes are created by the operating system before the child process is created. In the code snippet shown in (a), what are the program outputs at lines A, B, and C?
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