Progress bars and syscals

[Fireel <fireel gamta lt>]

Hello,

  Since i'm quite new to both C and Gtk, i met a problem which i am not 
able to solve. The     base  of the problem is that i have a task, which 
should fetch several files from the internet. When a button is pressed, 
a new window with a progress bar opens and indicates the progress of the 
task. Basicly, since i thought C is a linear language, i just added 
several system() calls and added gtk_progress_bar_set_fraction between 
them like so:

...
  system("wget file.a");
  gtk_progress_bar_set_fraction(GTK_PROGRESS_BAR(pb1), 0.3);
  system("wget file.b");
  gtk_progress_bar_set_fraction(GTK_PROGRESS_BAR(pb1), 0.6);  ...

and so on.

The result was that the program first executed the system calls, and 
only afterwards did it paint something or tampered with the progress bar.

Why? How to go around this? What to read?

Thank you,
Fireel