Subversion Repositories SvarDOS

                         === SVARCOM vs FREECOM ===

SvarCOM is a DOS command interpreter (shell), similar to COMMAND.COM in MS-DOS

and FreeCOM in FreeDOS. But why not using FreeCOM in the first place?

The FreeCOM project is an impressive piece of software, but there are a few

things that I do not like about it. SvarCOM is my attempt at addressing these

issues through a completely new implementation. SvarCOM is composed of

entirely original code and does not borrow any code from MS-DOS or FreeCOM.

=== MEMORY FOOTPRINT =========================================================

FreeCOM is not suitable for low-memory machines. It takes about 55K of

conventional memory when XMS is unavailable. XMS being a 386+ thing, FreeCOM

is a poor fit for pre-386 machines. There is the KSSF hack, but it is a kludge

with many limitations. As pointed out by one of the FreeCOM authors, FreeCOM

is designed with 21'st century machines in mind and not IBM PC compatibles.

SvarCOM does not rely on XMS and performs runtime swapping that works on any

IBM PC compatible machine. Its resident size is about 2K.

=== NLS RESSOURCES ===========================================================

FreeCOM requires custom NLS resources. While the vast majority of FreeDOS

programs use a single "standard" (CATS), FreeCOM uses a different approach

with NLS strings built into the binary. This makes it necessary to distribute

as many binary blobs as there are supported languages. Another consequence is

that FreeCOM is unable to switch its language dynamically (ie. following

changes made to the LANG environment variable). It also makes the translation

process more difficult.

SvarCOM uses CATS-style translations (through SvarLANG) and supports dynamic

language changes through the %LANG% environment variable.

=== CODE COMPLEXITY ==========================================================

FreeCOM is a complex beast: it aims for compatibility with multiple compilers

and supports many embedded features. This makes the code uneasy to follow and

changes require careful testing on all supported compilers and all possible

build variants.

SvarCOM, on the other hand, is meant to be simple and universal. It is

compiled with OpenWatcom only, which makes a ton of IFDEF's go away. It also

does not integrate extra features that can be reasonably implemented through

external tools (typically: DOSKEY). It strives to reimplement the baseline

functionality of MS-DOS 5/6.

=== NON-FREE LICENSE =========================================================

FreeCOM code is released under the terms of a license that restrains the

freedom of its users due to its virality (GPL).

SvarCOM is released under the terms of a liberal and permissive (MIT) license

that does not impose limitations on how users may or may not use the software,

it only asks for credits to be provided where credit is due.

I am aware that this section, and its slightly provocating title, may trigger

reactions from GPL enthusiasts. Let me explain with more words. I enjoy

creating software and I publish it for others to use for free. Should someone

wish to extend SvarCOM with an extra feature and decide not to publish the

source code along with the modified version, that's fine by me. My code is

still open and free. Theirs is not, but its their work, so I find it fair that

they have the freedom to decide how to distribute it. I certainly do not want

to impose my views on others.

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