# Multiple calculations in 4 processes using fork()

Write a program to create 4 processes: parent process and its child process which perform various tasks :

- Parent process count the frequency of a number
- 1st child sort the array
- 2nd child find total even number(s) in a given array
- 3rd child calculate the sum of even numbers in an array

**Example –**

Input :2, 4, 6, 7, 9, 0, 1, 5, 8, 3Output :Parent process : the key to be searched is 7 the frequency of 7 is 1 1st child process : the sorted array is 0 1 2 3 4 5 6 7 8 9 2nd child process : Total even no are: 5 3rd child process : the sum is :45

**Explanation –** Here, we had used fork() function to create 4 processes three child and one parent process. So, here we use two fork() function which create 4 process n1=fork() and n2 = fork()

- if n1 and n2 is greater than zero then it is parent process which counts the frequency of a number.
- if n1 is equal to zero and n2 is greater than zero then it is 1st child process which sorts the given array.
- if n1 is greater than zero and n2 is equal to zero than it is 2nd child process which finds the total even numbers in the array.
- if n1 and n2 both equal to zero then it is 3rd child calculates the sum of all elements in an array.

**Code –**

`// C++ code to demonstrate the calculation ` `// in parent and its 3 child processes using fork() ` `#include <iostream> ` `#include <unistd.h> ` ` ` `using` `namespace` `std; ` ` ` `int` `main() ` `{ ` ` ` ` ` `int` `a[10] = { 2, 4, 6, 7, 9, 0, 1, 5, 8, 3 }; ` ` ` `int` `n1, n2, i, j, key, c, temp; ` ` ` `n1 = fork(); ` ` ` `n2 = fork(); ` ` ` ` ` `// if n1 is greater than zero ` ` ` `// and n2 is greater than zero ` ` ` `// then parent process executes ` ` ` `if` `(n1 > 0 && n2 > 0) { ` ` ` ` ` `int` `c = 0; ` ` ` `cout << ` `"Parent process :"` `<< endl; ` ` ` ` ` `// key to be searched is 7 ` ` ` `key = 7; ` ` ` `cout << ` `"the key to be searched is "` `<< key << endl; ` ` ` ` ` `for` `(i = 0; i < 10; i++) { ` ` ` ` ` `if` `(a[i] == key) ` ` ` `// frequency of key ` ` ` `c++; ` ` ` `} ` ` ` ` ` `cout << ` `"the frequency of "` `<< key << ` `" is "` `<< c << endl; ` ` ` `} ` ` ` ` ` `// else if n1 is zero ` ` ` `// and n2 is greater than zero ` ` ` `// then 1st child process executes ` ` ` `else` `if` `(n1 == 0 && n2 > 0) { ` ` ` ` ` `cout << ` `"1st child process :"` `<< endl; ` ` ` ` ` `for` `(i = 0; i < 10; i++) { ` ` ` ` ` `for` `(j = 0; j < 9; j++) { ` ` ` ` ` `if` `(a[j] > a[j + 1]) { ` ` ` ` ` `temp = a[j]; ` ` ` `a[j] = a[j + 1]; ` ` ` `a[j + 1] = temp; ` ` ` `} ` ` ` `} ` ` ` `} ` ` ` ` ` `cout << ` `"the sorted array is"` `<< endl; ` ` ` ` ` `for` `(i = 0; i < 10; i++) { ` ` ` ` ` `cout << a[i] << ` `" "` `; ` ` ` `} ` ` ` ` ` `cout << endl; ` ` ` `} ` ` ` ` ` `// else if n1 is greater than zero ` ` ` `// and n2 is zero ` ` ` `// then 2nd child process executes ` ` ` `else` `if` `(n1 > 0 && n2 == 0) { ` ` ` ` ` `int` `f = 0; ` ` ` `cout << ` `"2nd child process :"` `<< endl; ` ` ` ` ` `for` `(i = 0; i < 10; i++) { ` ` ` ` ` `// counting total even numbers ` ` ` `if` `(a[i] % 2 == 0) { ` ` ` ` ` `f++; ` ` ` `} ` ` ` `} ` ` ` ` ` `cout << ` `" Total even no are: "` `<< f << ` `" "` `; ` ` ` `cout << endl; ` ` ` `} ` ` ` ` ` `// else if n1 is zero ` ` ` `// and n2 is zero ` ` ` `// then 3rd child process executes ` ` ` `else` `if` `(n1 == 0 && n2 == 0) { ` ` ` ` ` `cout << ` `"3rd child process :"` `<< endl; ` ` ` ` ` `int` `sum = 0; ` ` ` `// summing all given keys ` ` ` `for` `(i = 0; i < 10; i++) { ` ` ` ` ` `sum = sum + a[i]; ` ` ` `} ` ` ` ` ` `cout << ` `"the sum is :"` `<< sum << endl; ` ` ` `} ` ` ` ` ` `return` `0; ` `} ` |

*chevron_right*

*filter_none*

**Output –**

Parent process : the key to be searched is 7 the frequency of 7 is 1 1st child process : the sorted array is 0 1 2 3 4 5 6 7 8 9 2nd child process : Total even no are: 5 3rd child process : the sum is :45

This article is contributed by **Shivani Baghel**. If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.

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