<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <HTML ><HEAD ><TITLE >What is FreeTDS?</TITLE ><META NAME="GENERATOR" CONTENT="Modular DocBook HTML Stylesheet Version 1.79"><LINK REL="HOME" TITLE="FreeTDS User Guide" HREF="index.htm"><LINK REL="PREVIOUS" TITLE="About this User Guide" HREF="about.htm"><LINK REL="NEXT" TITLE="History of TDS Versions" HREF="tdshistory.htm"><LINK REL="STYLESHEET" TYPE="text/css" HREF="userguide.css"></HEAD ><BODY CLASS="CHAPTER" BGCOLOR="#FFFFFF" TEXT="#000000" LINK="#0000FF" VLINK="#840084" ALINK="#0000FF" ><DIV CLASS="NAVHEADER" ><TABLE SUMMARY="Header navigation table" WIDTH="100%" BORDER="0" CELLPADDING="0" CELLSPACING="0" ><TR ><TH COLSPAN="3" ALIGN="center" ><SPAN CLASS="PRODUCTNAME" >FreeTDS</SPAN > User Guide: A Guide to Installing, Configuring, and Running <SPAN CLASS="PRODUCTNAME" >FreeTDS</SPAN ></TH ></TR ><TR ><TD WIDTH="10%" ALIGN="left" VALIGN="bottom" ><A HREF="about.htm" ACCESSKEY="P" >Prev</A ></TD ><TD WIDTH="80%" ALIGN="center" VALIGN="bottom" ></TD ><TD WIDTH="10%" ALIGN="right" VALIGN="bottom" ><A HREF="tdshistory.htm" ACCESSKEY="N" >Next</A ></TD ></TR ></TABLE ><HR ALIGN="LEFT" WIDTH="100%"></DIV ><DIV CLASS="CHAPTER" ><H1 ><A NAME="WHAT" ></A >Chapter 1. What is <SPAN CLASS="PRODUCTNAME" >FreeTDS</SPAN >?</H1 ><DIV CLASS="TOC" ><DL ><DT ><B >Table of Contents</B ></DT ><DT ><A HREF="what.htm#TDSPROTOCOLHIST" >Background: The <ACRONYM CLASS="ACRONYM" >TDS</ACRONYM > Protocol and related <ACRONYM CLASS="ACRONYM" >API</ACRONYM >s</A ></DT ><DT ><A HREF="tdshistory.htm" >History of <ACRONYM CLASS="ACRONYM" >TDS</ACRONYM > Versions</A ></DT ><DT ><A HREF="freetdshistory.htm" >History of <SPAN CLASS="PRODUCTNAME" >FreeTDS</SPAN ></A ></DT ><DT ><A HREF="projects.htm" >Current Projects, Language Bindings, and Alternatives</A ></DT ></DL ></DIV ><P ><SPAN CLASS="PRODUCTNAME" >FreeTDS</SPAN > is an open source (or free software if you prefer) programming library, a re-implementation of the Tabular Data Stream protocol. It can be used in place of Sybase's <SPAN CLASS="SYSTEMITEM" >db-lib</SPAN > or <SPAN CLASS="SYSTEMITEM" >ct-lib</SPAN > libraries. It also includes an <SPAN CLASS="SYSTEMITEM" >ODBC library</SPAN >. It allows many open source applications such as <SPAN CLASS="PRODUCTNAME" >Perl</SPAN > and <SPAN CLASS="PRODUCTNAME" >PHP</SPAN > (or your own C or C++ program) to connect to Sybase or Microsoft <SPAN CLASS="PRODUCTNAME" >SQL Server</SPAN >. </P ><P ><SPAN CLASS="PRODUCTNAME" >FreeTDS</SPAN > is distributed in source code form, and is expected to compile on just about any operating system. That means every form of Unix® and Unix-like™ system (including notable variants such as Interix® and QNX®), as well as Win32®, VMS®, and OS X®. If it doesn't compile on your system — and you're not using MS-DOS® — it's probably considered a bug. </P ><DIV CLASS="SECT1" ><H1 CLASS="SECT1" ><A NAME="TDSPROTOCOLHIST" >Background: The <ACRONYM CLASS="ACRONYM" >TDS</ACRONYM > Protocol and related <ACRONYM CLASS="ACRONYM" >API</ACRONYM >s</A ></H1 ><P ><ACRONYM CLASS="ACRONYM" >TDS</ACRONYM > is a <I CLASS="FIRSTTERM" >protocol</I >, a set of rules describing how to transmit data between two computers. Like any protocol, it defines the types of messages that can be sent, and the order in which they may be sent. Protocols describe the <SPAN CLASS="QUOTE" >"bits on the wire"</SPAN >, how data flow. </P ><P >In reading this manual, it may be helpful to keep in mind that a protocol is not an <ACRONYM CLASS="ACRONYM" >API</ACRONYM >, although the two are related. The server recognizes and speaks a protocol; anything that can send it the correct combination of bytes in the right order can communicate with it. But programmers aren't generally in the business of sending bytes; that's the job of a library. Over the years, there have been a few libraries — each with its own <ACRONYM CLASS="ACRONYM" >API</ACRONYM > — that do the work of moving SQL through a <ACRONYM CLASS="ACRONYM" >TDS</ACRONYM > pipe. <SPAN CLASS="SYSTEMITEM" >ODBC</SPAN >, <SPAN CLASS="SYSTEMITEM" >db-lib</SPAN >, and <SPAN CLASS="SYSTEMITEM" >ct-lib</SPAN > have very different <ACRONYM CLASS="ACRONYM" >API</ACRONYM >s, but they're all one to the server, because on the wire they speak <ACRONYM CLASS="ACRONYM" >TDS</ACRONYM >. </P ><P >The <ACRONYM CLASS="ACRONYM" >TDS</ACRONYM > protocol was designed and developed by Sybase Inc. for their Sybase <SPAN CLASS="PRODUCTNAME" >SQL Server</SPAN > relational database engine in 1984. The problem Sybase faced then still exists: There was no commonly accepted application-level protocol to transfer data between a database server and its client. To encourage the use of their product, Sybase came up with a flexible pair of products called <SPAN CLASS="PRODUCTNAME" >netlib</SPAN > and <SPAN CLASS="SYSTEMITEM" >db-lib</SPAN >. </P ><P ><SPAN CLASS="PRODUCTNAME" >netlib</SPAN >'s job was to ferry data between the two computers. To do that, it had to deal with the underlying network protocol. Remember, in those days <ACRONYM CLASS="ACRONYM" >TCP/IP</ACRONYM > was not the ubiquitous thing it is today. Besides <ACRONYM CLASS="ACRONYM" >TCP/IP</ACRONYM >, <SPAN CLASS="PRODUCTNAME" >netlib</SPAN > ran on <ACRONYM CLASS="ACRONYM" >DECnet</ACRONYM >, <ACRONYM CLASS="ACRONYM" >IPX/SPX</ACRONYM >, <ACRONYM CLASS="ACRONYM" >NetBEUI</ACRONYM > and the like. </P ><P ><SPAN CLASS="SYSTEMITEM" >db-lib</SPAN > provided an <ACRONYM CLASS="ACRONYM" >API</ACRONYM > to the client program, and communicated with the server via <SPAN CLASS="PRODUCTNAME" >netlib</SPAN >. What <SPAN CLASS="SYSTEMITEM" >db-lib</SPAN > sent to the server took the form of a stream of bytes, a structured stream of bytes meant for tables of data, a Tabular Data Stream. </P ><P >In 1990 Sybase entered into a technology sharing agreement with Microsoft which resulted in Microsoft marketing its own <SPAN CLASS="PRODUCTNAME" >SQL Server</SPAN >. Microsoft kept the <SPAN CLASS="SYSTEMITEM" >db-lib</SPAN > <ACRONYM CLASS="ACRONYM" >API</ACRONYM > and added <SPAN CLASS="SYSTEMITEM" >ODBC</SPAN >. (Microsoft has since added other <ACRONYM CLASS="ACRONYM" >API</ACRONYM >s, too.) At about the same time, Sybase introduced a more powerful <SPAN CLASS="QUOTE" >"successor"</SPAN > to <SPAN CLASS="SYSTEMITEM" >db-lib</SPAN >, called <SPAN CLASS="SYSTEMITEM" >ct-lib</SPAN >, and called the pair <SPAN CLASS="PRODUCTNAME" ><I CLASS="FIRSTTERM" >OpenClient</I ></SPAN >. </P ><P > <SPAN CLASS="SYSTEMITEM" >ct-lib</SPAN >, <SPAN CLASS="SYSTEMITEM" >db-lib</SPAN >, and <SPAN CLASS="SYSTEMITEM" >ODBC</SPAN > are <ACRONYM CLASS="ACRONYM" >API</ACRONYM >s that — however different their programming style may be — all use <SPAN CLASS="PRODUCTNAME" >netlib</SPAN > to communicate to the server. The language they use is <ACRONYM CLASS="ACRONYM" >TDS</ACRONYM >. </P ><P >The <ACRONYM CLASS="ACRONYM" >TDS</ACRONYM > protocol comes in several flavors, most of which have never been openly documented. If anything, it's probably considered to be something like a trade secret, or at least proprietary technology. The exception is TDS 5.0, used exclusively by Sybase, for which documentation is available <A HREF="http://crm.sybase.com/sybase/www/ESD/tds_spec_download.jsp" TARGET="_top" >from Sybase</A >. </P ></DIV ></DIV ><DIV CLASS="NAVFOOTER" ><HR ALIGN="LEFT" WIDTH="100%"><TABLE SUMMARY="Footer navigation table" WIDTH="100%" BORDER="0" CELLPADDING="0" CELLSPACING="0" ><TR ><TD WIDTH="33%" ALIGN="left" VALIGN="top" ><A HREF="about.htm" ACCESSKEY="P" >Prev</A ></TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" ><A HREF="index.htm" ACCESSKEY="H" >Home</A ></TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" ><A HREF="tdshistory.htm" ACCESSKEY="N" >Next</A ></TD ></TR ><TR ><TD WIDTH="33%" ALIGN="left" VALIGN="top" >About this User Guide</TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" > </TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" >History of <ACRONYM CLASS="ACRONYM" >TDS</ACRONYM > Versions</TD ></TR ></TABLE ></DIV ></BODY ></HTML >
