Cross-compilers - Microsoft C Cross Compilers - 1987

1987

C programs had long been linked with modules written in assembly language. Most C compilers (even current compilers) offer an assembly language pass (that can be tweaked for efficiency then linked to the rest of the program after assembling).

Compilers like Aztec-C converted everything to assembly language as a distinct pass and then assembled the code in a distinct pass, and were noted for their very efficient and small code, but by 1987 the optimizer built into Microsoft C was very good, and only "mission critical" parts of a program were usually considered for rewriting. In fact, C language programming had taken over as the "lowest-level" language, with programming becoming a multi-disciplinary growth industry and projects becoming larger, with programmers writing user interfaces and database interfaces in higher-level languages, and a need had emerged for cross language development that continues to this day.

By 1987, with the release of MSC 5.1, Microsoft offered a cross language development environment for MS DOS. 16 bit binary object code written in assembly language (MASM) and Microsoft's other languages including Quick Basic, Pascal, and Fortran could be linked together into one program, in a process they called "Mixed Language Programming" and now "InterLanguage Calling". If BASIC was used in this mix, the main program needed to be in BASIC to support the internal run-time system that compiled BASIC required for garbage collection and its other managed operations that simulated a BASIC interpreter like QBasic in MS DOS.

The calling convention for C code in particular was to pass parameters in "reverse order" on the stack and return values on the stack rather than in a processor register. There were other programming rules to make all the languages work together, but this particular rule persisted through the cross language development that continued throughout Windows 16 and 32 bit versions and in the development of programs for OS 2, and which persists to this day. It is known as the Pascal calling convention.

Another type of cross compilation that Microsoft C was used for during this time was in retail applications that require handheld devices like the Symbol Technologies PDT3100 (used to take inventory), which provided a link library targeted at an 8088 based barcode reader. The application was built on the host computer then transferred to the handheld device (via a serial cable) where it was run, similar to what is done today for that same market using Windows Mobile by companies like Motorola, who bought Symbol.