Final Test: Operating Systems

The grade formula is as follows:

Grade = 0.4 * Theory + 0.6 * Programming

Part 1. Theoretical Questions

Answer the theoretical questions in a few sentences (1-2 paragraphs for a question).

Use your own words. Copy-paste from external sources and other students will result in 100% penalty.

1. Memory management.
   • What ways to allocate memory do you know?
   • How dynamic memory allocation is implemented in C?
   • How does memory mapping and shared memory work?
2. Processes and threads.
   • Give definitions of process and thread.
   • What is the difference between them?
   • What inter-process communication mechanisms do you know?
   • What synchronization mechanisms do you now?
3. Permissions.
   • What Linux files types to you know?
   • What access rights and permission groups do you know?
   • Study the output of the ls -li command below.

   • What can you say about file1, file2, and file3?

     acos@acos-vm:~/folder$ ls -li
     total 44
     268508 -rwsr-xr-x 2 myuser acos 16832 июн 17 14:04 file1
     262605 drwxr-xr-- 1 acos   acos  4096 июн 17 14:08 file2
     268508 -rwsr-xr-x 2 myuser acos 16832 июн 17 14:04 file3
     

Part 2. Programming Task

Write a program in C that does the following:

• Calculates the value of the specified function in the range from argv[1] to argv[2] with step argv[3].
• Writes pairs <function argument>, <function result>) into text file output.csv (CSV format).
• The function to be calculated has the following format:

  f(x) = f0(f1(x), f2(x), f3(x), f4(x))
  

  , where:

  • x is the function argument;
  • f0-f4 are functions that are individual according to the variant.

Requirements:

• Execute f0 in the parent process and f1-f4 in separate child processes. Return the calculated values of f1-f4 to f0 using IPC (a pipe or other type of IPC you like).

Hints

• Functions f1-f4 have the following structure:

  double f1(double x) {
      return <math expr>;
  }
  

• Command-line arguments (strings) can be converted to double using the atof function.
• Mathematical functions (such as sin, cos, pow, exp etc.) and constants (M_E) are provided in the math.h library.
• Programs using library <math.h> must be linked with the m library: use the -lm GCC flag.
• Use the fopen, fprintf, and fclose functions to write data to the file.
• Multi-process calculations:
  • Child: a function is calculated for a range of values and results are written to IPC;
  • Parent: values are read from IPC in a loop and printed or used in other calculations.

Variants

Choose your variant number according to your number in the list of students.

Note: the ^ symbol means “power”.

---

Variant

f0(a, b, c, d) = (a - b + c - d) / 2
f1(x) = 2*x^3 - 4*x^2 + 3*x + 1
f2(x) = sin(5*x)*4 + 3
f3(x) = 1 / (1 + e^(-7*x))
f4(x) = 2^x + 5