1. Variable Storage Compatibility and Equivalence (Character vs Integer vs Short vs Float vs Complex; variable's Word Size) - elements of Inter-Program Communications; character data and complex variables can be special cases
2. Array Compatibility (A special case of Variable Storage Compatibility and Equivalence above) - indexing, dimensioning, row major or column major.  See also IC-POINT-ARRAY and IC-POINT-ARRAY-REDEF in COBOL Files - COBOL 3.0, PowerCOBOL 3.0, Silverfrost FTN95, and Numerical Recipes and Pascal Arrays.
3. Case Sensitivity (may affect compiler options) C, C++, D, and XBLite (XBasic Lite) are case sensitive; COBOL, FORTRAN, and Pascal are case insensitive - variable/subprogram name lower case letters may be automatically converted to upper case; D's extern (Pascal) {...} can affect case sensitivity
4. Variables passed By Reference (basically, variable's address passed; address unmodifiable), By Value (subprogram uses a local copy), or By Pointer (variable's address passed; address modifiable).  XBLite is an example of a language that can pass parameters by all three methods.  C uses By Value and By Pointer; Pascal and Lazarus By Value and By Reference; FORTRAN defaults to By Reference.
5. Calling Model (Standard Call vs cdecl; other calling mechanisms include register, interrupt, pascal, safecall, and oldfpccall)
6. The order the passed arguments are Pushed/Popped to/from the stack (sometimes called passed left-to-right or right-to-left).  This is one of several considerations in both D calling FORTRAN and D calling Pascal.
7. Function/Procedure/Subroutine name mangling - some programming languages/compilers will mangle a subprogram's name internally (.lib file and .dll file), though any source code written for that programming language/compiler can refer to the unmangled name.  For example, the DMD D compiler will mangle procedure name hEditInitMsg(...) to D6hedtio12hEditInitMsgFNbPvZv (...).  Use Dependency Walker to determine a procedure's mangled name (if any).
8. Import Libraries - some compilers require an import library (*.lib) while others do not.  Two incompatible formats are used - COFF and Intel 32 bit OMF.  Fujitsu COBOL (and XBLite via GoAsm & Linker) generates and requires Microsoft 32 bit Linker compatible COFF import libraries, Silverfrost FTN95 SLINK can generate Microsoft 32 bit Linker compatible COFF import libraries.  Digital Mars D compiler generates and requires Intel 32 bit OMF import libraries (fortunately, they supply a free utility, implib, to generate an OMF import library from a *.dll).  Free Pascal and Lazarus do not require import libraries.

Tutorials

COBOL Program Structure and Elements: Structure, keywords, data definition, and executable statements of a COBOL program.
FORTRAN Program Structure and Elements: Layout, keywords, specification statements, and executable statements of a FORTRAN program.⁵
Pascal Program Structure and Elements: Covers Pascal Main Programs, Pascal Units, Lazarus Object Pascal Units, and Object Pascal Libraries.⁵
Appending Text to Windows Edit Control: done on the Windows API level, written in Object Pascal; should be able to port the Win32 API calls to other programming languages.  Includes downloads of Object Pascal Library source files, compiling instructions, code snippets of showing how to use.
Using Lazarus Tab Sheets (TPageControl & TTabSheet): Uses a real world example of calculating Coefficients of Normal Force and Centers of Pressure for a multi-stage rocket to demonstrate Tab Controls.

• Overview - Combining Fujitsu COBOL 3.0, PowerCOBOL 3.0, Silverfrost FTN95, and Numerical Recipes: The Art of Scientific Computing : Using a COBOL "wrapper" around FORTRAN subroutines to calculate Average, Median, Standard Deviation, and Variance (Statistics Analysis).
• COBOL Files - Combining Fujitsu COBOL 3.0, PowerCOBOL 3.0, Silverfrost FTN95, and Numerical Recipes: The Art of Scientific Computing : The COBOL "wrapper" - source files, compiling, and linking. Includes downloads of some COBOL source files.
• FORTRAN File - Combining Fujitsu COBOL 3.0, PowerCOBOL 3.0, Silverfrost FTN95, and Numerical Recipes: The Art of Scientific Computing (Statistics Analysis) : The FORTRAN backend (sttstcs.dll) - source file, compiling, and linking.   sttstcs.dll is used in multiple projects.

• Using Fujitsu COBOL 3.0 to call the USPS Address Matching System API (USPS AMS API) : Describes how to call C++ functions from a COBOL main program on the Win32 platform.  Uses the Fujitsu COBOL 3.0 compiler and the USPS AMS API as an example.  Shows how to define the AMS API ZIP4_PARM C++ struct as a COBOL record (can be downloaded below).  Includes compiling and linking options.
• Combining Fujitsu COBOL 3.0, PowerCOBOL 3.0, and the USPS Address Matching System API : Describes one solution to interfacing a Fujitsu PowerCOBOL 3.0 GUI application with a C++ library on the Win32 platform.  This is a practical application of the Using Fujitsu COBOL 3.0 to call the USPS Address Matching System API (USPS AMS API) tutorial above.  Includes compiling and linking options.  This example demonstrates combining COBOL's file processing strengths with a third party API.  Includes downloads of many COBOL source files.

• D Programming Language, Silverfrost Fortran 95, and Numerical Recipes : Describes how to call FORTRAN subprograms using a simple command line Digital Mars D main program.  Differences between D, Pascal, and FORTRAN arrays and matrices, using D extern statements, and passing parameters.
• D Windows program, Silverfrost Fortran 95, and Numerical Recipes : Describes how to call FORTRAN subprograms in a Windows program written in D.  Includes downloads of the D source files.
• FORTRAN File - Combining Digital Mars D main program, Silverfrost FTN95, and Numerical Recipes: The Art of Scientific Computing (Statistics Analysis) : The FORTRAN backend - source file, compiling, and linking.  This is the same FORTRAN sttstcs.dll used in COBOL calling FORTRAN .dll.

• D .dll, Silverfrost Fortran 95, and Numerical Recipes : Some pointers of writing D .dll's, D interface files, and calling FORTRAN subprograms from a D .dll.  Compiling and linking the D .dll. Includes downloads of the D source files.
• FORTRAN FILE - D .dll, Silverfrost Fortran 95, and Numerical Recipes (Simulated Annealing) : mathproc.dll - the FORTRAN backend - source file, compiling, and linking.   mathproc.dll contains engineering, mathematic, and scientific subprograms, used in several projects.

• D Programming Language, Free Pascal, and Financial Functions : Describes how to call Pascal functions and procedures using a simple command line Digital Mars D main program.  D extern statements, data type equivalency, passing parameters By Reference or By Value, cdecl, and stdcall.
• Pascal File - D Programming Language, Free Pascal, and Financial Functions : Sample Pascal backend - source file, compiling, linking, side effects of D's extern (Pascal) {...}, and import library creation.  Includes downloads of source file and .bat file to compile source file.

• D .dll Calling Free Pascal .dll - D Files : Command Line Parameter Parsing D module CmdLine front end; pragma statements.  Includes download of D module source files.
• D .dll Calling Free Pascal .dll - Pascal Files : Command Line Parameter Parsing Object Pascal Library ALlazrs back end; import library creation.  Includes downloads of Pascal source files.

• D main program calling XBLite Library : D command console program calling XBLite elliptical functions; brief introduction/demonstration of hypergeometric functions.  Includes download of XBasic source file, listing of D program.

• Command line Free Pascal and Silverfrost Fortran 95 : Describes how to call FORTRAN subprograms using Pascal command console programs, including passing arrays.  Includes download of sample Pascal program.
• Simple Free Pascal Windows Program, Pascal Library, DMD D, and Silverfrost Fortran 95 : Describes how to call FORTRAN Functions (NROOT (...) in sttstcs.dll) as well as D procedures (hEditInitMsg(...) in module hedtio) using its D mangled name from a Pascal Windows program.  Using Dependency Walker to find a procedure's mangled name.  Calling a D function declared extern (C).  Includes downloads of sample Pascal program, Pascal Library, FORTRAN Function, and D module.
• Pascal .dll calling FORTRAN engineering subroutines in mathproc.dll : Uses an example of calculating rocket Coefficients of Normal Force and Centers of Pressure (also has brief introduction to rocket stability) to demonstrate Pascal .dll calling FORTRAN.  Includes downloads of Pascal Library (missle02.dll) and FORTRAN subprograms extracted from mathproc.dll.  (The download source files are being regularly enhanced.  New versions will be uploaded as they are completed.)

• Lazarus, Free Pascal, Silverfrost FTN95, and Numerical Recipes: The Art of Scientific Computing : This is basically an updated, enhanced, and more functional implementation of STF95COB.  Like Fujitsu PowerCOBOL 3.0, Lazarus is event driven programming and can present data in table form.  Where Fujitsu COBOL 3.0 programs need an interface subprogram (INVKSHT.COB and F5BBRUNS.DLL) to use PowerCOBOL sheets, Lazarus program ST95DLPH needs an user written Free Pascal LIBRARY nrlazrs procedure rMoment (...) to call the Numerical Recipes FORTRAN subprograms.  Includes downloads of Lazarus program source files, Pascal Library, and include files.
• FORTRAN File - Silverfrost FTN95 and Numerical Recipes: The Art of Scientific Computing (Statistics Analysis) : The FORTRAN backend - source file, compiling, and linking.  While this is the same FORTRAN sttstcs.dll used in COBOL calling FORTRAN .dll, different subprograms, AVEVAR (...) and MDIAN2 (...), are called.
• Lazarus Sub-forms, Grid Cell Background Color, StringGrid Cell Editor, and Calling FORTRAN : Introduction to Lazarus sub-forms; changing the cell background color in a TStringGrid; using a cbsEllipsis Editor Style in a TStringGrid; and Lazarus calling FORTRAN via Object Pascal .dll.  Part of an actual application to input and analyze a model rocket design.  Uses Pascal missle02.dll (see above) to call mathproc.dll FORTRAN subprograms and Pascal nrlazrs.dll (see above) to call sttstcs.dll FORTRAN subprograms.
• Lazarus Sub-forms, Calling FORTRAN, Software Re-use, and Aerodynamics : Another example of Lazarus sub-forms and calling FORTRAN via Object Pascal.  Detailed example of software re-use.  Part of an actual application to input and analyze model rocket design - adding Parallel Stages to a rocket's launch configuration.  Via Object Pascal, calls FORTRAN subroutines to calculate parallel stage surface area and estimate impact on Coefficient of Normal Force and Center of Pressure.
  (Many of the download source files are regularly enhanced.  New versions will be uploaded as they are completed.)

Additional Downloads

USPS AMS API C struct ZIP4_PARM translated to COBOL Record layout : As described in the Using Fujitsu COBOL 3.0 to call the USPS Address Matching System API tutorial above.  Conforms to the Address Matching System API User Guide July 2003.   This is a 01 Level record.   Can be used as an include file in the DATA DIVISION WORKING-STORAGE SECTION or LINKAGE SECTION with the statement INCLUDE "AMSZ4PRM.COB".   Contains line sequence numbers, which can be removed using the COBOL Line Numbering Utility (download link below).

COBOL Line Numbering Utility : An extremely simple COBOL source file line number manipulation utility that can be downloaded and modified (includes source code, written in Visual Basic 2.0).   Runs on both Win16 and Win32 platforms (pre Win Vista) (if anyone upgrades this to a later version of VB, please email to me).

Silverfrost Fortran 95 subprogram to compute Nth Root of X : FORTRAN function (including source code) to compute ^N √ X  .

Miscellaneous mathematical subprograms in mathproc.dll : FORTRAN functions and subroutines (including source code) for Point Rotation, Triangular Segment Area, Signum (return sign of argument), Quadratic Roots, Synthetic Division, and Cubic Polynomial Roots extracted from mathproc.for.