SAS System Totally Explained

Everything about Sas System totally explained

SAS (pronounced "sass", originally Statistical Analysis System) is an integrated system of software products provided by SAS Institute that enables the programmer to perform:

data entry, retrieval, management, and mining
report writing and graphics
statistical analysis
business planning, forecasting, and decision support
operations research and project management
quality improvement
applications development
Data warehousing (extract, transform, load)
platform independent and remote computing

In addition, SAS has many business solutions that enable large scale software solutions for areas such as IT management, human resource management, financial management, business intelligence, customer relationship management and more.

Description of SAS

SAS is driven by SAS programs that define a sequence of operations to be performed on data stored as tables. Although non-programmer graphical user interfaces to SAS exist (such as the SAS Enterprise Guide), most of the time these GUIs are just a front-end to automate or facilitate generation of SAS programs. SAS components expose their functionalities via application programming interfaces, in the form of statements and procedures.
   A SAS program is composed of three major parts, the DATA step, procedure steps (effectively, everything that isn't enclosed in a DATA step), and a macro language. SAS Library Engines and Remote Library Services allow access to data stored in external data structures and on remote computer platforms.
   The DATA step section of a SAS program, like other database-oriented fourth-generation programming languages such as SQL or Focus, assumes a default file structure, and automates the process of identifying files to the operating system, opening the input file, reading the next record, opening the output file, writing the next record, and closing the files. This allows the user/programmer to concentrate on the details of working with the data within each record, in effect working almost entirely within an implicit program loop that runs for each record.
   All other tasks are accomplished by procedures that operate on the data set (SAS' terminology for "table") as a whole. Typical tasks include printing or performing statistical analysis, and may just require the user/programmer to identify the data set. Procedures are not restricted to only one behavior and thus allow extensive customization, controlled by mini-languages defined within the procedures. SAS also has an extensive SQL procedure, allowing SQL programmers to use the system with little additional knowledge.
   There are macro programming extensions, that allow for rationalization of repetitive sections of the program. Proper imperative and procedural programming constructs can be simulated by use of the "open code" macros or the SAS/IML component.
   Macro code in a SAS program, if any, undergoes preprocessing. At runtime, DATA steps are compiled and procedures are interpreted and run in the sequence they appear in the SAS program. A SAS program requires the SAS software to run.
   Compared to general-purpose programming languages, this structure allows the user/programmer to be less familiar with the technical details of the data and how it's stored, and relatively more familiar with the information contained in the data. This blurs the line between user and programmer, appealing to individuals who fall more into the 'business' or 'research' area and less in the 'information technology' area, since SAS doesn't enforce (although SAS recommends) a structured, centralized approach to data and infrastructure management.
   SAS runs on IBM mainframes, Unix machines, OpenVMS Alpha, and Microsoft Windows; and code is almost transparently moved between these environments. Older versions have supported PC-DOS, the Apple Macintosh, VMS, VM/CMS, Data General AOS and OS/2.

Early history of SAS

SAS was conceived by Anthony J. Barr in 1966. As a North Carolina State University graduate student from 1962 to 1964, Barr had created an analysis of variance modeling language inspired by the notation of statistician Maurice Kendall, followed by a multiple regression program that generated machine code for performing algebraic transformations of the raw data. Drawing on those programs and his experience with structured data files, he created SAS, placing statistical procedures into a formatted file framework. From 1966 to 1968, Barr developed the fundamental structure and language of SAS. In January 1968, Barr and James Goodnight collaborated, integrating new multiple regression and analysis of variance routines developed by Goodnight into Barr's framework. Goodnight's routines made the handling of basic statistical analysis more robust, and his later implementation (in SAS 76) of the general linear model greatly increased the analytical power of the system. By 1971, SAS was gaining popularity within the academic community. And by 1972, industry was making use of SAS. One strength of the system was analyzing experiments with missing data, which was useful to the pharmaceutical and agricultural industries, among others. In 1973, John Sall joined the project, making extensive programming contributions in econometrics, time series, and matrix algebra. Other participants in the early years included Caroll G. Perkins, Jolayne W. Service, and Jane T. Helwig. Perkins made programming contributions. Service and Helwig created the early documentation.. The DATA step was implemented. Regression and analysis of variance were the main uses of the program.

SAS 72

This more robust release was the first to achieve wide distribution. It included a substantial user's guide, 260 pages in length. The MERGE statement was introduced in this release, adding the ability to perform a database JOIN on two data sets. This release also introduced the comprehensive handling of missing data.

SAS 76

SAS 76 was a complete system level rewrite, featuring an open architecture for adding and extending procedures, and for extending the compiler. The INPUT and INFILE statements were significantly enhanced to read virtually all data formats in use on the IBM mainframe. Report generation was added through the PUT and FILE statements. The capacity to analyze general linear models was added.

79.3 - 82.4

1980 saw the addition of SAS/GRAPH, a graphing component; and SAS/ETS for econometric and time series analysis. In 1981 SAS/FSP followed, providing full-screen interactive data entry, editing, browsing, retrieval, and letter writing.
In 1983 full-screen spreadsheet capabilities were introduced (PROC FSCALC).
For IBM mainframes, SAS 82 no longer required SAS databases be DSORG=DAU, because SAS 82 removed location-dependent information from databases. While this may seem trivial, it eliminated a major headache in administering SAS--that restoring a SAS disk-base database from tape no longer required restoring the entire volume, then copying the database to another location.

Version 4 series

In the early 1980s, SAS Institute released Version 4, the first version for non-IBM computers. It was written mostly in a subset of the PL/I language, to run on several minicomputer manufacturers' operating systems and hardware: Data General's AOS/VS, Digital Equipment's VAX/VMS, and Prime Computer's PRIMOS. The version was colloquially called "Portable SAS" because most of the code was portable, for example, the same code would run under different operating systems.

Version 5 series

Version 6 series

Version 6 represented a major milestone for SAS. While it was superficially similar to the user, the major change was "under the hood", where the software was rewritten. From its FORTRAN origins, followed by PL/I and mainframe assembly language; in version 6 SAS was rewritten in C, to provide enhanced portability between operating systems, as well as access to an increasing pool of C programmers compared to the shrinking pool of PL/I programmers.
   This was the first version to run on UNIX, MS-DOS and Windows platforms. The DOS versions were incomplete implementations of the Version 6 spec: some functions and formats were unavailable, as were SQL and related items such as indexing and WHERE subsetting. DOS memory limitations restricted the size of some user-defined items.
   The mainframe version of SAS 6 changed the physical format of SAS databases from "direct files" (DSORG=DA) to "flat files" (DSORG=PS,RECFM=FS). The practical benefit of this change is that a SAS 6 database can be copied from any media with any copying tool.
   In 1984 a project management component was added (SAS/OR?).
   In 1985 SAS/AF software, econometrics and time series analysis (SAS/ETS) component, and interactive matrix programming (SAS/IML) software was introduced. MS-DOS SAS (version 6.02) was introduced, along with a link to mainframe SAS.
   In 1986 Statistical quality improvement component is added (SAS/QC software); SAS/IML and SAS/STAT software is released for personal computers. 1987 saw concurrent update access provided for SAS data sets with SAS/SHARE software. Database interfaces are introduced for DB2 and SQL-DS.
   In 1988 MultiVendor Architecture (MVA) concept is introduced; SAS/ACCESS software is released. Support for UNIX-based hardware announced. SAS/ASSIST software for building user-friendly front-end menus is introduced. New SAS/CPE software establishes SAS as innovator in computer performance evaluation. Version 6.03 for MS-DOS is released.
   6.06 for MVS, CMS, and OpenVMS is announced in 1990. The same year, the last MS-DOS version (6.04) is released.
   Data visualization capabilities added in 1991 with SAS/INSIGHT software.
   In 1992 SAS/CALC, SAS/TOOLKIT, SAS/PH-Clinical, and SAS/LAB software is released.
   In 1993 software for building customized executive information systems (EIS) is introduced. Release 6.08 for MVS, CMS, VMS, VSE, OS/2, and Windows is announced. 1994 saw the addition of ODBC support, plus SAS/SPECTRAVIEW and SAS/SHARE*NET components.
   6.09 saw the addition of a data step debugger.
   6.09E for MVS.
   6.10 in 1995 was a Microsoft Windows release and the first release for the Apple Macintosh. Version 6 was the first, and last series to run on the Macintosh. JMP, also produced by the SAS Institute, is the software package the company produces for the Macintosh.
   Also in 1995, 6.11 (codenamed Orlando) was released for Windows 95, Windows NT, and UNIX.
   6.12 were Unix and Microsoft Windows releases (and more?)
   (Some of the following milestones in this sub-section may belong under version 7 or 8.)
   In 1996 SAS announces Web enablement of SAS software. Scalable performance data server is introduced.
   In 1997 SAS/Warehouse Administrator and SAS/IntrNet software goes into production. 1998 sees SAS introduce a customer relationship management (CRM) solution, and an ERP access interface — SAS/ACCESS interface for SAP R/3. SAS is also the first to release OLE-DB for OLAP and releases HOLAP solution. Balanced scorecard, SAS/Enterprise Reporter, and HR Vision are released. First release of SAS Enterprise Miner. 1999 sees the releases of HR Vision software, the first end-to-end decision-support system for human resources reporting and analysis; and Risk Dimensions software, an end-to-end risk-management solution. MS-DOS versions are abandoned because of Y2K issues and lack of continued demand.
   In 2000 SAS shipped Enterprise Guide and ported its software to Linux.

Version 7 series

The Output Delivery System debuted in version 7; as did long variable names (from 8 to 32 characters); storage of long character strings in variables (from 200 to 32,767); and a much improved built-in text editor, the Enhanced Editor.
Version 7 saw the synchronisation of features between the various platforms for a particular version number (which previously hadn't been the case).
Version 7 was a precursor to version 8. It was believed SAS Institute released a snapshot from their development on version 8 to meet a deadline promise. SAS Institute recommended that sites wait until version 8 before deploying the new software.

Version 8 series

Released about 1999; 8.0, 8.1, 8.2 were Unix, Microsoft Windows, CMS (z/VM) and z/OS releases. Key features: long variable names, Output Delivery System (ODS).
SAS 8.1 was released in 2000.
SAS 8.2 was released in 2001.

Version 9 series

In version 9, SAS Institute added the SAS Management Console, parallel processing, JavaObj, ODS OO (experimental as opposed to alpha), and National Language Support.
   Again the SAS Institute recommended sites delay deployment until 9.1.
   SAS Version 9 is running on Windows (32 & 64 bit), Unix (64 bit), Linux, and z/OS. Support for CMS (z/VM) was dropped.
   SAS 9.1 was released in 2003.
   SAS 9.1.2 was released in 2004.
   SAS 9.1.3 was released in 2005.
   SAS 9.2 is the latest release (March 2008) and was demonstrated at SAS Global Forum (previously called SUGI) 2008(External Link

). A list of features added to this release of SAS can be seen at the "What's New in SAS" web page(External Link

).
SAS 9.2 will be released incrementally in three phases:
1) MVA-based products eg. SAS/BASE, SAS/STAT, SAS/Graph. Nothing that relies on metadata. Limited availability from March 2008 because most users rely on the Metadata Server (see Phase 2) or products released in Phased 3.
2) Enterprise Intelligence Platform. Metadata Server for Business Intelligence (BI) and Data Integration. Availability from around August 2008.
3) Client software for metadata driven analytics and business solutions. Enterprise Miner, Text Miner, Model manager. Solutions include Financial, Retail, Health & Life Science. Availability unknown, probably 2nd Quarter 2009.
There are several important additions to base SAS in Version 9. The new hash object now allows functionality similar to the MERGE statement without sorting data or building formats. The function library was enlarged, and many functions have new parameters. Perl Regular Expressions are now supported, as opposed to the old "Regular Expression" facility, which was incompatible with most other implementations of Regular Expressions. Long format names are now supported.

Criticism

SAS had been criticized for its relatively poor graphics when compared with other statistical software packages. With the release of the Output Delivery System (ODS) for Statistical Graphics extension in SAS 7, the graphics have improved significantly. Critics also cite the existence of free alternatives (such as DAP and R) that have similar statistics functionality. The SAS Platform delivers comprehensive data integration, business intelligence, and analytical capabilities beyond just the statistical functions of these free tools.

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