Tick inidicator Denis

[Zombie Night]

https://www.mql5.com/en/articles/60

I don't know why when previously calculated==0 the code assumes there are ticks in the file and reads the first line of string or it reads till end of the file and processes the string only if line is more than 6. I thought there will be no ticks in the file. I drop on my chart an it works but I don't know how can someone explain. 

if(prev_calculated==0)
  {
   // Reading the first line from the file and determine the length of a string
   line_string_len=StringLen(FileReadString(file_handle))+2;
   // if file is large (contains more quotes than rates_total/2)
   if(FileSize(file_handle)>(ulong)line_string_len*rates_total/2)
     {
      // Setting file pointer to read the latest rates_total/2 quotes
      FileSeek(file_handle,-line_string_len*rates_total/2,SEEK_END);
      // Moving file pointer to the beginning of the next line
      FileReadString(file_handle);
     }
   // if file size is small
   else
     {
      // Moving file pointer at the beginning of a file
      FileSeek(file_handle,0,SEEK_SET);
     }
   // Reset the counter of stored quotes
   ticks_stored=0;
   // Reading until the end of the file
   while(FileIsEnding(file_handle)==false)
    {
      // Reading a string from the file
      file_buffer=FileReadString(file_handle);
      // Processing of string if its length is larger than 6 characters
      if(StringLen(file_buffer)>6)
        {
         // Finding the start position of Bid price in the line
         BidPosition=StringFind(file_buffer," ",StringFind(file_buffer," ")+1)+1;
         // Finding the start position of Ask price in the line
         AskPosition=StringFind(file_buffer," ",BidPosition)+1;
         // If the Bid line should be plotted, adding this value to BidBuffer[] array
         if(BidLineEnable) 
         BidBuffer[ticks_stored]=StringToDouble(StringSubstr(file_buffer,BidPosition,AskPosition-BidPosition-1));
         // If the Ask line should be plotted, adding this value to AskBuffer[] array
         if(AskLineEnable) 
         AskBuffer[ticks_stored]=StringToDouble(StringSubstr(file_buffer,AskPosition));
         // Increasing the counter of stored quotes
         ticks_stored++;
        }
     }
  }

[Oleksandr Medviediev]

The code you provided is handling a scenario where there are no previously calculated data points ( prev_calculated == 0 ).

Your code is attempting to read and process data from a file.

[Zombie Night]

@Oleksandr Medviediev  why is it reading from a file if the file got zero ticks