Those programs may be given a way to access this data, often through libraries, but it would not work with any other database engine, or even different databases in the same engine. Data from dBASE could not generally be accessed directly by other programs running on the machine. Instead, the data was accessed directly by the program – a programming library in the case of large mainframe systems, or a command line interface or interactive forms system in the case of dBASE and similar applications. Older mainframe databases, and the newer microcomputer based systems that were based on them, generally did not have a SQL-like command processor between the user and the database engine. Dynamic SQL systems became a major focus for SQL vendors during the 1980s. The SQL market referred to this as static SQL, versus dynamic SQL which could be changed at any time, like the command-line interfaces that shipped with almost all SQL systems, or a programming interface that left the SQL as plain text until it was called. Another key problem to the Embedded SQL concept was that the SQL code could only be changed in the program's source code, so that even small changes to the query required considerable programmer effort to modify. Like the different varieties of SQL, the Embedded SQLs that used them varied widely, not only from platform to platform, but even across languages on one platform – a system that allowed calls into IBM Db2 would look very different from one that called into their own SQL/DS. There were several problems with the Embedded SQL approach. Results returned from the statements would be interpreted back into C data formats like char * using similar library code. For instance, a SQL statement like SELECT * FROM city could be inserted as text within C source code, and during compiling it would be converted into a custom format that directly called a function within a library that would pass the statement into the SQL system. This led to the concept of Embedded SQL, which allowed SQL code to be embedded within another language. Since the SQL language had only rudimentary programming features, users often wanted to use SQL within a program written in another language, say Fortran or C. The introduction of SQL aimed to solve the problem of language standardization, although substantial differences in implementation remained. These systems may or may not allow other applications to access the data directly, and those that did use a wide variety of methodologies. The best-known examples are SQL from IBM and QUEL from the Ingres project. Generally these systems operated together with a simple command processor that allowed users to type in English-like commands, and receive output. The introduction of the mainframe-based relational database during the 1970s led to a proliferation of data access methods. The CLI remains similar to ODBC, and applications can be ported from one platform to the other with few changes. Full ODBC was later ported back to those platforms, and became a de facto standard considerably better known than CLI. ODBC retained several features that were removed as part of the CLI effort. ODBC was originally developed by Microsoft and Simba Technologies during the early 1990s, and became the basis for the Call Level Interface (CLI) standardized by SQL Access Group in the Unix and mainframe field. Drivers exist for all major DBMSs, many other data sources like address book systems and Microsoft Excel, and even for text or comma-separated values (CSV) files. Any ODBC-compliant application can access any DBMS for which a driver is installed. An application that can use ODBC is referred to as "ODBC-compliant". An ODBC driver can be thought of as analogous to a printer driver or other driver, providing a standard set of functions for the application to use, and implementing DBMS-specific functionality. The application uses ODBC functions through an ODBC driver manager with which it is linked, and the driver passes the query to the DBMS. ODBC accomplishes DBMS independence by using an ODBC driver as a translation layer between the application and the DBMS. An application written using ODBC can be ported to other platforms, both on the client and server side, with few changes to the data access code. The designers of ODBC aimed to make it independent of database systems and operating systems. In computing, Open Database Connectivity ( ODBC) is a standard application programming interface (API) for accessing database management systems (DBMS). ODBC, standard interface for accessing database systems
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