CSCI215-Assignment 2 Processes Solved

Question 1 ­ Program trace

Consider the following program:

int main (int arg, char * argv [])

{ int i, j, p; for (i = 0; i <3; i ++) if ((p = fork ()) == 0){ printf( "i =% d \ n", i)

j = 0;

while ((j < i) && ((p = fork ()) == 0)) j ++; if (p == 0) printf ( "j =% d \ n", j);

exit(j);

}/ * if * / return (0);

}

 

Note: Assume that all process creations succeed

 

How many child processes are created upon executing this program?

Represent the family tree of processes and give the output of each process.

Write a modified version of this code which guarantees that the original parent process (the one created by function main) will only terminate once all its descendants have terminated.

 

Question 2 ­ Hacking the magic square
 

A magic square is a square matrix where adding up the values in each row, column, or diagonal will produce the same result. For example, a matrix whose entries all share the same value is necessarily magic.

 

Consider the following 3x3 matrix of integer values in [0 .. 9]:

{{4 a, 8}, {b, c, d}, {2, e, 6}};

 

Write a program that searches for sets of values { a, b, c, d, e} that make this matrix a magic square. Your program will use brute force: the main program creates 10 child processes, assigns each of them a different value for a, and then waits for their termination. Each child will then fill the array depending on its assigned value, and check whether the resulting square is magic: if it is, the child will then display the matrix.

 

You can use the skeleton code decoder.c to implement your solution.

 

Question 3 ­ Multi­Currency Converter
 

Write a program multi_converter that converts an amount expressed in any one of a set of predefined currencies (see header file converters.h and its implementation converters.c), and displays the result of converting this amount to all the currencies in the set.

The conversion parameters are passed to the program by the user via the command line in the following format:

$ multi_converter <currency <amount

 

currency represents the input currency amount represents the amount to be converted in the target currencies.

 

Your program shall operate as follows. The parent process retrieves the parameter values entered by the user, creates one child process per target currency, and then waits until all of its children terminate to notify the end of the conversion. Each child process handles a different target currency and displays the conversion result.

 

Output example:

./multi_converter CNY "100.0" Conversion for: CNY 100.000

EUR 13.336

GBP 11.186

USD 15.009

JPY 1521.564

CNY 100.000

End of conversion