free c/c++ compilers
Latest version of excellent Inprise's compiler now completely free for download.

A freeware C compilers for 6502 based systems.
This is a C-compiler for Microchip (PIC) and Scenix (SX) microcontrollers. It works under MS Windows 95/98/ME/NT/2000 and has a built-in user interface.
cc65 is a C compiler that was originally adapted for the Atari 8bit computers by John R. Dunning. It is a Small C descendant but has several extensions, and some of the limits of the original Small C compiler are gone.
Ch from SoftIntegration, Inc. is a superset of C interpreter. It is the most complete C interpreter in existence for scripting. Ch can interface with C/C++ binary libraries and be embedded in other application programs. It supports 1990 ISO C Standard (C90), major features in C99, classes in C++, POSIX, X11/Motif, OpenGL, ODBC, XML, GTK+, CGI, 2D/3D graphical plotting, socket/Winsock, and shell programming. It can run in Windows, Solaris, Linux and HP-UX. The extensions in Ch provide the simplest solution for numerical computing and visualization in C/C++ domain.
Cilk is a language for multithreaded parallel programming based on ANSI C. Cilk is designed for general-purpose parallel programming, but it is especially effective for exploiting dynamic, highly asynchronous parallelism, which can be difficult to write in data-parallel or message-passing style. Using Cilk, our group has developed three world-class chess programs, StarTech, Socrates, and Cilkchess. Cilk provides an effective platform for programming dense and sparse numerical algorithms, such as matrix factorization and N-body simulations, and we are working on other types of applications. Unlike many other multithreaded programming systems, Cilk is algorithmic, in that the runtime system employs a scheduler that allows the performance of programs to be estimated accurately based on abstract complexity measures.
CINT is a C/C++ interpreter aimed at processing C/C++ scripts. Scripts are programs performing specific tasks. Generally execution time is not critical, but rapid development is. Using an interpreter the compile and link cycle is dramatically reduced facilitating rapid development. CINT makes C/C++ programming enjoyable even for part-time programmers.
CScript is a small C scripting language compiler. It's syntax is very similar to C. The source code of CScript can also be compiled by other C/C++ compilers, just like Visual C++.
Digital Mars C and C++ Compilers for Win32, Win16, DOS32 and DOS.
Fastest compile/link times, powerful optimization technology, Design by Contract, complete library source, HTML browsable documentation, disassembler, librarian, resource compiler, make, etc., command line and GUI versions, tutorials, sample code, online updates, and much more.
DJGPP is a complete 32-bit C/C++ development system for Intel 80386 (and higher) PCs running DOS. It includes ports of many GNU development utilities. The development tools require a 80386 or newer computer to run, as do the programs they produce. In most cases, the programs it produces can be sold commercially without license or royalties.
eC is a subset C++ compiler that is designed for use by high schools and junior colleges. The features were chosen to facilitate the transition from Pascal to C++. For example, the compiler doesn't support some commonly misused features of C++ such as the embedded assignment operator ( if (a=b) ) and pointer arithmetic. The runtime implements extensive checking.
This is a pointer-safe, bytecode C interpreter, useful for teaching, fast-prototyping of new programs and research. It catches most types of array bounds violations. It can be run both interactively and non-interactively. It implements most of ISO C. It comes with source code, and supports the following platforms: Linux, Solaris, SunOS, Alpha/OSF, IRIX, HP-UX, NetBSD, FreeBSD, and Windows 95/98/NT.
The GNU C compiler packaged with this system allows you to create 32 bit programs for MSDOS and OS/2 2.x and 3.x. The OS/2 programs can even be Presentation Manager applications. For the MSDOS programs, a 32 bit dos extender is provided.
GCC for SPARC Systems extends GCC to be able to use the latest, performance optimizing Sun Code Generator for SPARC systems. Supports GCC and Sun Studio command line options.
The Intel C/C++ compiler is designed to deliver the performance and features of Intel's latest processors, including the Intel Pentium III processor. It uses advanced compiler technique and an intimate understanding of the hardware to deliver outstanding application performance. It plugs into Microsoft Visual Studio and is source and object compatible with Microsoft Visual C++. 30-days free eval copy available.
lcc is a retargetable compiler for Standard C. It generates code for the ALPHA, SPARC, MIPS R3000, and Intel x86 and its successors.
MinGW is a collection of header files and import libraries that allow one to use GCC and produce native Windows32 programs that do not rely on any 3rd-party DLLs. The current set of tools include GNU Compiler Collection (GCC), GNU Binary Utilities (Binutils), GNU debugger (Gdb), GNU make, and a assorted other utilities.
The Miracle C Compiler runs under MS-Windows targeting MSDOS. All traditional C syntax is implemented, including record (struct/union) and enumerated data types, int, long and floating point data types, user type definition, bit fields in structs, initializers for all data types. There is a comprehensive library of functions, some example programs demonstrating compiler features and Windows Helpfile documentation is supplied with the package. Miracle generates object for Microsoft or compatible linker (such a linker is builtin to the Workbench).
The x86 Open64 compiler system is a high performance, production quality code generation tool designed for high performance parallel computing workloads. The x86 Open64 environment provides the developer the essential choices when building and optimizing C, C++, and Fortran applications targeting 32-bit and 64-bit Linux platforms. The x86 Open64 compiler system offers a high level of advanced optimizations, multi-threading, and processor support that includes global optimization, vectorization, interprocedural analysis, feedback directed optimizations, loop transformations, and code generation which extracts the optimal performance from each x86 processor core.
The x86 Open64 Compiler Suite simplifies and accelerates development and tuning for x86, AMD64 (AMD® x86-64 Architecture), and Intel64 (Intel® x86-64 Architecture) applications. The x86 Open64 compilers create a strong foundation for building robust, high performance parallel code through MPI, OpenMP®, and auto-parallelization along with highly optimized libraries*.

* See Release Notes regarding parallel code generation
OpenC++ is a version of C++ with a Metaobject Protocol. In other words, it is a tool of source-code translation for C++. Programmers can easily implement various kinds of translation so that they can define new syntax, new annotation, and new object behavior. OpenC++ is useful if they need, for example, Developing extensions to C++, to provide support for things like parallelism, distribution, concurrency, and persistence. Adding domain-, application-, or class-specific compiler optimizations. Building their own version of (runtime) MOP for C++.
Open SPHiNX C-- Compiler is a set of compiler and libraries based on the "SPHiNX C--" programming language created by Peter Cellik.
Pacific C is a freeware C compiler for DOS. Included is the HI-TECH Professional Development environment, an IDE allowing you to edit source code and manage projects with ease. Pacific C's text-based GUI makes it an excellent teaching package, while ANSI-compliance and tight code generation provide a powerful development tool. We have decided to make Pacific C for MS-DOS freeware.
The HI-TECH PICC Lite compiler is a freeware version of our industrial-strength PICC compiler. There are no code size or optimization limitations placed on the PICC Lite compiler, other than its restriction to the PIC16F627, PIC16C84, 16F84 and 16F84A devices.
Reads51 is an integrated applications software development system, which runs on an IBM PC or compatible host. Reads51 allows writing, compiling, assembling, debugging, downloading, and running applications software in the MCS-51 language. Reads51 contains a C compiler, relative assembler, linker/locator, editor, chip simulator, assembly language debugger, and host-to-board communications in a user-friendly, menu-driven environment.
SDCC is a Freeware, retargettable, optimizing ANSI - C compiler that targets the Intel 8051, Maxim 80DS390, Zilog Z80 and the Motorola 68HC08 based MCUs. Work is in progress on supporting the Microchip PIC16 and PIC18 series. The entire source code for the compiler is distributed under GPL.
This is the definitive collection of Small-C related information and source code. Dr. Dobb's Journal would like to extend a special thanks Ron Cain, James Hendrix, Andy Yuen, and all other programmers around the world who have contributed to the Small-C project, including Randy Dumse of New Micros, Inc. who provided NMI ports of the Small-C compiler.
Peter Sphinx Cellik, the author of this free C++ and assembler alike language has made the final version available through many famous software archives on the internet. SPHINX C-- claims to be more readable than assembler (similar to C) and produce fast programs. In this package are the compiler, examples, some informations and source.
High-performance, optimizing C, C++, and Fortran compilers for the Solaris OS on SPARC and x86/x64 platforms, plus command-line tools and a NetBeans-based Integrated Development Environment (IDE) for application performance analysis and debugging of mixed source language applications. Multi-platform support, compatible with gcc, Visual C++, C99, OpenMP, and Fortran 2003.
Opensource version of the good old Watcom compiler.