C Run-time Library History and Naming Conventions

ID: Q28173

The information in this article applies to:

The C Run-Time (CRT), included with:
- Microsoft C for MS-DOS, versions 6.0, 6.0a, 6.0ax
- Microsoft C/C++ for MS-DOS, version 7.0
- Microsoft Visual C++ for Windows, versions 1.0, 1.5, 1.51, 1.52
- Microsoft Visual C++, 32-bit Editions, versions 1.0, 2.0, 2.1, 4.0

SUMMARY

This articles describes the naming conventions used by the C Run-time libraries included with the products listed above.

The standard 16-bit CRT libraries are named using the following convention: xLIBCy?.LIB, where:

"x" represents the memory model option. The different memory model options are "S" for the small memory model (the default), "M" for the medium memory model, "C" for the compact memory model, and "L" for the large memory model.

"y" represents the math library option. The different math library options are "E" for the emulator model (the default), "7" for the coprocessor model, and "A" for the alternate model.

"?" represents an operating mode. The operating modes are "R" for real mode, "P" for protected mode, and "W" for Microsoft Windows mode. When this position is empty, the library is a default mode library.

The 32-bit CRT libraries are LIBC.LIB, LIBCMT.LIB, and MSVCRT.LIB.

MORE INFORMATION

16-bit Library Specifics

The 16-bit Microsoft CRT libraries support 4 memory models:

Small. There is one data segment and one code segment. This is the default memory model.

Medium. There is one data segment and multiple code segments.

Compact. There are multiple data segments and one code segment.

Large. There are multiple data segments and multiple code segments.

The memory model is specified with the compiler options /AS, /AM, /AC, and /AL, respectively.

The 16-bit Microsoft CRT libraries support 3 floating point options:

Floating point emulation. This library uses an Intel math coprocessor if one is present in the system and emulates a coprocessor otherwise. This is the default.

Coprocessor math. An Intel math coprocessor must be present in the system. This model has a speed advantage over the emulation model because the code is not required to test for the presence of a coprocessor chip. The disadvantage of the model is that the coprocessor chip is required.

Alternate math. This library performs an alternate math coprocessor emulation. This library does not use a math coprocessor chip, even if one is available in the system.

The floating point option is specified with the compiler options /FPi, /FPi87, and /FPa, respectively.

Library Search Records

In an effort to ease the linking process for the user, the compiler puts a search record into the object (.OBJ) file that tells the linker what libraries are required to link the application. The search record lists only the standard libraries. Other libraries, like GRAPHICS.LIB, are not included.

When the search record is present, the user is not required to explicitly list libraries on the linker command line unless additional libraries are required or if the /NOD switch is specified on the linker command line. (/NOD instructs the linker to ignore the search record in the .OBJ file.) You can prevent the compiler from placing a search record into the .OBJ file by specifying the /Zl compiler option switch.

By default, SLIBCE.LIB is used. This is because small memory model, emulator math, and no specified operating mode are the defaults.

The compiler option switches /Lr, /Lp, /Ld, and /Lw direct the compiler to generate other library names in the library search record. For example the compiler command line:

cl /Lr test.c

generates a library search record for SLIBCER.LIB in the object file.

C versions 6.x

The CRT libraries provided are:


   xLIBCy?.LIB  - Standard CRT libraries. Described under Summary.

   API.LIB      - FAPI (Family Application Programming Interface)
                  routines. Applications that use only FAPI functions
                  can run with either MS-DOS or OS/2.

   CDLLOBJS.LIB - OS/2 dynamic-link library (DLL) run-time library
                  objects

   CDLLSUPP.LIB - OS/2 DLL support

   CRTCOM.LIB   - Tiny memory model library (Used to generate COM
                  files)

   EXTSUP.LIB   - Programmer's WorkBench (PWB) library (Used to build
                  applications that extend PWB)

   GRAPHICS.LIB - MS-DOS text mode graphics support

   GRTEXTP.LIB  - OS/2 text mode graphics support

   LLIBCDLL.LIB - OS/2 DLL support

   LLIBCMT.LIB  - OS/2 multi-threaded DLL support

   OS2.LIB      - OS/2 system calls library

   PGCHART.LIB  - Presentation graphics support

C/C++ versions 7.0 and 7.0a

The C/C++ version 7.0 CRT adds support for the Microsoft Windows operating system and removes support for OS/2. The CRT libraries provided are:


   xLIBCy?.LIB  - Standard CRT libraries. Described under Summary.

   CRTCOM.LIB   - Tiny memory model library (Used to generate COM
                  files)

   GRAPHICS.LIB - MS-DOS text mode graphics support

   MOVETR.LIB   - Microsoft Overlaid Virtual Environment (MOVE)
                  library with TRACE.EXE support

   PGCHART.LIB  - Presentation graphics support

   xDLLCyW.LIB  - DLL library for Windows environment

   xLIBCyWQ.LIB - QuickWin application library

   xNOCRTDW.LIB - DLL initialization code library

   xNOCRTW.LIB  - Application initialization code for the Windows
                  environment

Visual C++ for Windows, versions 1.0 and 1.5x

The CRT libraries in Visual C++ for Windows are identical to the libraries included in C/C++ version 7.0.

Visual C++ 32-bit Edition, version 1.0

The CRT libraries provided are:


   LIBC.LIB     - Single-threaded C run-time library support

   LIBCMT.LIB   - Multi-threaded C run-time library support

   MSVCRT.LIB   - Import library for the multi-threaded CRT in a DLL.
                  To run code linked with this library, the DLL
                  MSVCRT10.DLL must be available at run time.

Visual C++ 32-bit Edition, versions 2.x and 4.0

The CRT libraries provided are identical to those provided in Visual C++ 32- bit Edition 1.0. However, the import library MSVCRT.LIB now refers to the DLL MSVCRT20.DLL for Visual C++ 2.x and either MSVRCT40.DLL or MSVCR40D.DLL for Visual C++ 4.0. MSVCR40D.DLL is a debug version of the DLL for Windows NT and Windows 95 (Win32). In addition, with Visual C++ 2.1 and above, there are two versions of MSVCRTx0.DLL: one that targets Win32 and the other that targets Win32s.

REFERENCES

For information on the naming convention of the Microsoft Foundation Classes (MFC) libraries, please see the following article in the Microsoft Knowledge Base:

Q88113 Compile and Link Requirements for MFC Applications

and MFC Technical Note 33.

Additional query words: 1.00 1.50 1.51 1.52 2.00 2.10 4.00 6.00 6.00a 6.00ax 7.00 kbinf

Keywords : kbCRT kbVC
Version : winnt:1.0,2.0,2.1,4.0
Platform : winnt
Issue type :