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1. Check the extension

First of all we can check the extension of the file ( the part of the filename after the dot). This is not absolute because filenames may be lost by a data transfer but it may be useful for existing files on your computer. Also you have to remember that for most systems the extension will guide the software to use a precise converter. So better keep your files with correct extensions:

	IGES:	.iges, .igs
	DXF:	.dxf
	SET:	.set
	STEP:	.step, .stp
	UNISURF:	.uni

2. Check the contents of the file.

Because the filename might be lost or convention may be different it is sometimes necessary to guess the type of standard by looking at the file. Some CAD systems are able to detect the file type by themselves but if they fail you will have to inspect it yourself to find a solution. Also the header of the file may contain information about the sender and the system used.

Hopefully all standard format are ASCII. It means that they are human readable. One of the major problems is that it might be difficult to read it in a text editor. The file might be very large and all on one line due to line feed problems.

Everywhere in this page underscore _ is a placeholder for space.

For UNIX users more is a good solution.

sh>more myfile

will show the first lines of the file

For windows users ...

Once you got the file look at the 10 first lines or 400 first characters

IGES

Start Section is free form. It must end with an S in column 72 _________S______1
:,,10HFILE18.IGS,10HFIKE18.IGS,07HCADCAMX,10HPREPROC1.0,32,38,7,133,16,_G______1
10HFILE18.IGS,1.,2,02HMM,1,1.,13H961129.105425,10.E-6,1.E3,08HANYWHERE, G______2
06HANYONE,4,0;_________________________________________________________ G______3     

	Lines should be 80 characters long.
	On the 72th column the five sections will be indicated by a letter, followed by the line number.
	The first lines belong to the start section letter S followed by the global section : letter G. You can get the extra informations from the global section:

Exchange File format

We mean here ASCII file format (files you can read with any text editor). Exchange means that there is not too much data lost in the transfer.