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Wickenhäuser µC/51 (Freeware)

A superoptimizing ANSI-C compiler for the whole 8051 family for your free use. There will be no future updates and we can't give any support!

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8051 C-Compiler uC51 The 8051 C-Compiler uC51 is well known for it's high quality and high density code. You can develop high quality software for any 8051 in ANSI C. µC/51 comes with an incredible optimizing compiler, you can even write software in ANSI C on 8051's with 1kB of code memory! µC/51 captivates by its user-friendly multi file editor, compiler, assembler, downloader, source level debugger. It's a complete toolchain - You won't need anything else.


  • Superior code quality
  • Full ANSI compatible
  • Very low price
  • FREE 8kB limited demo
  • TCP/IP Stack with 100% Sourcecode included
  • OMF51 Source Level Debugging on SiLabs CPUs

Target support

  • All 8051's are supported, no specific assumptions
  • Different memory models exactly meet your demands
  • Full 32-bit IEEE floating point support
  • Write interrupt handlers in C
  • Access up to 16 MB code and address space
  • Place global objects in any space: direct internal RAM, indirect internal RAM, external RAM, code, bit

ANSI C Compiler

  • Full support for the ANSI C language. NOT a reduced subset of C or extended K&R C.
  • Especially designed for ext. Harvard architectures
  • Include assembly language in your C programs
  • compiler writes 100% assembler sourcecode
  • Integral support for source level debugging
  • Superior code quality due to powerful optimizer


  • Fast macro assembler with rich directives
  • Access assembler functions from C


  • Strip linker compresses the code to the minimum
  • Output formats: binary and Intel Hex (more soon...)

Downloader / source level debugger

  • Complete OS for downloading programs on development boards (RAM) included as source code
  • Write programs to a Flash memory
  • C level single line stepping
  • Terminal program included


  • Subset of ANSI C library (including strings and printf())
  • I2C bus librarie with complete sourcecode
  • Open printf()-formatter (i.e. write your own lcd_printf())

Included demos

  • Many demo sourcecodes included, up to a FFT (Fast Fourier Transformation)
  • Demos for generic 8051's, Infineon's C515, Texas Instrument's MSC1210, Analog Devices ADuC8xx, ...

Compare with the competitors

Download their demos from their websites:
K----: 2kB restricted (no floating point),
R----------: 4kB restricted (floating point):

  • Sieve (Sieve of Erathostenes):
    µC/51 V1.20: 142 Bytes Modul, 897 Bytes total
    K---- V6.21: 165 Bytes Modul, 1261 Bytes total
  • FFT (full sourcecode included, floating point required):
    µC/51 V1.10: 6257 Bytes total
    R---------- V6.1: 6735 Bytes total (demo won't save)


Software Details uC51
Software updates no updates
Supported operation systems Windows 98SE, ME, 2000, XP, 2003, Vista
Languages English