Loading Bar?

How do you make those loading bar things that show how much is loaded? How do I make it so the bar increases a bit everytime something has finished loading(an image or a music file)?

-thanks

graphics 640,480
size = filesize("filename.dat") ;total length of the file.

infile = readfile("filename.dat")

while not eof(infile)
 readdata() ;read some data from the file.
 p = filepos(infile)
 rect 0,0,(640*p)/size,40,1 
wend

Just off the top of my head, but something like that should work

For the theory part:
1. You have to know how many files you have to load
2. load file by file
3. After each file has been loaded you calculate the percentage of files loaded in comparison to maximum
4. You draw some kind of output

Another examplecode (only checking for complete files loaded):

Graphics 640, 480, 16, 2
SetBuffer BackBuffer()

total = 100

Dim files(total)

For i = 1 To total
	files(i) = CreateImage(320,320) ; Create or Load files/media
	Cls
	Text 320, 240, "Loading...", True, True
	Rect 240, 280, Float(i) / Float(total) * 160, 20, True
	Flip
Next

Store each frame of the loading bar in a separate image (or use anim image). Here is how I did it, though it isn't as good as Grisu's code.

DrawImage loading1, 100,100
img1 = LoadImage("img1.bmp")
img2 = LoadImage("img2.bmp")
Cls
DrawImage loading2, 100, 100
img3 = LoadImage("img3.bmp")
img4 = LoadImage("img4.bmp")
Cls
DrawImage loading3, 100,100

Though Grisu's code is so much more practicle.

Or try something like this:

function load_progress(percent#)
 setbuffer frontbuffer()
 xrel#=graphicswidth()/640.0
 yrel#=graphicsheight()/480.0
 rect 0,(graphicsheight()/2.0)-(10.0*yrel) ,6.4*xrel#*percent, 20.0*yrel, 1
 setbuffer backbuffer()
end function

now you can insert some calls to this function between the loading steps, eg:

load_progress(20)
;load meshes...
load_progress(40)
; load sounds etc.
load_progress(60)
; initialize network
load_progress(80)
; initialize player
load_progress(100)
; start main game loop