AXE Hex Editor FAQ

Over the years, there have been hundreds of questions asked about AXE by email, but there has never been anywhere to actually express the answers to these questions or generate discussion. Unfortunately, the existing AXE site seems unlikely to move in that direction in the immediate future so I have collected together the most important question here.

These questions refer to the current version of AXE, 3.4. There is really no reason to use 3.0 through 3.3 any more. AXE 4.0 development is dealt with in a separate page here.

What is the biggest file AXE can handle?

I say it with shame but the biggest file you can edit with AXE is about 1.3Gb. There are good reasons for this (at least, they were good back when AXE was first being developed) which I would like to explain.

When AXE was first developed ten years ago, and the AXE Way of Doing Things was evolving, most people were using windows 95 of a 200Mhz computer. Whenever there was a tradeoff between functionality and speed, AXE chose speed; one of the big features of AXE at that time was that it was a fast, smooth editing experience at a time when that was very rare in a hex editor. So AXE didn't do any paging on large files; what it did was give you the 'huge file' option which is described below. As a result, editing files in the 100Mb to 1Gb range (i.e. too big to fit in physical memory, but not too big to fit in virtual memory) was and is very very fast in AXE. The tradeoff was that the file has to fit in virtual memory.

Back then, that was a very advantageous tradeoff. But in the intervening 10 years, data has gotten bigger and CPUs have gotten faster. AXE 4 uses paging and has effectively no file size limit, and that's the way it should be.

What is meant by a 'huge file', then?

When you open a file in 'huge file' mode in AXE 3, the entire file is mapped to virtual memory. This means that AXE edits the file in-place; any change you make is immediately reflected on the disk without you pressing 'save'. At the time it was implemented, this was much the fastest solution. Of course, in-place editing has downsides and since the whole file is mapped at once, the file size can be no bigger than the largest available block of virtual memory address space (usually 1.3Gb on Windows NT/XP). It's a useful feature but it's straight out of the early 90s.