simulation of telephone system

input: list of "new calls"

import "new call" from queue
update "arrival time" of "new call"
if (any "end" of "call in progress" <= "arrival time" of "new call"){
    // process the call from "call in progress"
    turn off the flag of the sources of ended call in "lines" list;
    update "used" in "links";
    update "clock";
    remove the ended call from "call in progress";
    update "processed" & "completed" in "call counter";
}
else{
    if (any one source of "new call" is connected with another source in "call in progress"){
        // add the new call to busy
        update "clock";
        update "processed" & "busy" in "call counter";
        import "new call" from queue;
        update "arrival time" of "new call";
    }
    else if (all the rooms are full in "call in progress"){
        // add the new call to blocked
        update "clock";
        update "processed" & "blocked" in "call counter";
        import "new call" from queue;
        update "arrival time" of "new call";
    }
    else{
        // add the new call to "call in progress"
        turn on the flag of the sources of "new call" in "lines" list;
        update "used" in "links";
        update "clock";
        add the call to "call in progress";
        import "new call" from queue;
        update "arrival time" of "new call";
    }
}