Code has function specific variables changing values outside of scope - c++

Question

This is FCFS cpu scheduling algorithm.
void findTurnAroundTime(int processes[], int n, int bt[], int wt[], int tat[])
{
// Calculating turnaround time by adding bt[i] + wt[i]
for (int i = 0; i < n; i++)
tat[i] = bt[i] + wt[i];
}
// Function to calculate average waiting and turn-around
// times.
void findavgTime(int processes[], int n, int bt[], int at[])
{
int wt[n], tat[n];
// Function to find waiting time of all processes
findWaitingTime(processes, n, bt, wt, at);
// Function to find turn around time for all processes
findTurnAroundTime(processes, n, bt, wt, tat);
// Display processes along with all details
cout << "Processes " << " Burst Time " << " Arrival Time "
<< " Waiting Time " << " Turn-Around Time "
<< " Completion Time \n";
int total_wt = 0, total_tat = 0;
for (int i = 0; i < n; i++)
{
total_wt = total_wt + wt[i];
total_tat = total_tat + tat[i];
int compl_time = tat[i] + at[i];
cout << " " << i + 1 << "\t\t" << bt[i] << "\t\t" << at[i] << "\t\t"
<< wt[i] << "\t\t " << tat[i] << "\t\t " << compl_time << endl;
}
cout << "Average waiting time = " << (float) total_wt / (float) n;
cout << "\nAverage turn around time = " << (float) total_tat / (float) n;
}
How are variables like wt and tat connected if they are decleared inside each function?(This is the main question)
full code is working.

Answer 1

How are variables like wt and tat connected if they are decleared inside each function?
wt and tat are defined in findavgTime. (They are defined using a non-standard extension but that's a separate issue).
When findavgTime calls findWaitingTime and findTurnAroundTime, it passes those variables to the functions. The functions don't define them in their function body -- they are defined in the functions by way of function arguments. Since wt and tat are arrays, they decay to a pointer to the first elements of the respective arrays when findWaitingTime and findTurnAroundTime are called. Because of that, any changes made to the variables inside those functions are visible in findavgTime too.
You don't have to use the same variable names in the function arguments. You could use
void findTurnAroundTime(int processes[], int n, int bt[], int wt_here[], int tat_here[])
{
for (int i = 0; i < n; i++)
tat_here[i] = bt[i] + wt_here[i];
}
That won't change the behavior of the program.