COBOL and .NET Data Types

Article description 

.NET  has created a new, level playing field for a multitude of programming languages to interact on a scale never before seen. In order to accomplish this feat though several new features had to designed and implemented such as a Common Language Runtime (CLR), and the Microsoft Intermediate Language (MSIL).  The runtime also enforces code robustness by implementing a strict type- and code-verification infrastructure called the common type system (CTS). The CTS ensures that all managed code is self-describing. The various Microsoft and third-party language compilers generate managed code that conforms to the CTS. This means that managed code can consume other managed types and instances, while strictly enforcing type fidelity and type safety.
But COBOL has been around long before the development of the CTS. How can existing COBOL developers and their code base interact with the new CTS? During the development phase of NetCOBOL for .NET Fujitsu Software paid attention to this issue and was able to identify how existing COBOL data types would "marshal" or integrate with the new .NET data types. In most cases the CTS type and the COBOL representation are obvious.

Take for example an integer data type. In COBOL integers are specified as PIC 9 and then have a length designator to quantify the extent of the information they will contain, such as PIC 9(10). In the .NET environment there are two basic integer types, INT16 and INT32. Both represent an integer but of different lengths. An INT16 is a 16-bit signed integer while an INT32 is a 32-bit signed integer. The COBOL representation of these integer types is PIC S9(04) COMP-5 and PIC S9(09) COMP-5, respectively.

One of the more common issues is "What does a PIC X convert to in .NET?"  The obvious answer would be a String data type. This is in fact true, the .NET compiler inserts automatic conversion (called coercions) between the COBOL variables and the CLR strings. What the developer has to be aware of though is when you define a STRING in .NET the length of the string by default is 8192 bytes. You may only require a string to be 10 characters long but when you use a String definition you need to be aware you are getting much more than you bargain for. While this may not be an issue in most cases, when you move that string definition back into an existing COBOL data type of PIC X(10) and there is data beyond the 10th character, it will be lost due to truncation. The developer needs to be aware of issues such as this when intermixing the data types. Users also have to be aware that the COBOL runtime is performing ANSI to Unicode conversions.

The table below gives the NetCOBOL for .NET data type that corresponds to the .NET data types. It also states whether the usage type is VALUE or REFERENCE and gives a brief description of the data type. You can locate the table in the Visual Studio .NET documentation after you have installed the Fujitsu NetCOBOL for .NET compiler. Search the Fujitsu NetCOBOL documentation for "COBOL Representations". It may be a good idea to locate and print this table and keep it handy as a reference.

For additional information, see the table in the topic "Introduction to the .NET Framework Class Library" in the Visual Studio .NET documentation for a mapping of the .NET types to other languages such as Visual Basic and C# - a lot of the .NET Framework documentation uses the Visual Basic and C# data type names when describing an item's type.