Free software tools for embedded systems

Notes:

Though many of these programs are Open Source, links have been given (where possible) to pre-compiled, ready-to-run binaries.
Many DOS programs can run inside a Microsoft Windows DOS box, under FreeDOS, or under Linux DOSEMU.
Too many developers confuse DOS with the Win32 console, so I can't be sure whether some tools are true DOS programs or actually Win32 console executables.
Most compilers include an assembler for the CPU they target.

assemblers

target CPU/OS	host OS
	DOS	Win32	Linux
various	Alan R. Baldwin's ASxx
x86	NASM MASM	NASM	NASM
Motorola 680x0
Motorola ColdFire
Motorola/IBM PowerPC
ARM
MIPS
Hitachi SuperH (SH)
Hitachi H8
Atmel AVR	Tom's AVR Assembler	Tom's AVR Assembler AVRA	Tom's AVR Assembler^[s] AVA^[s]
Texas Instruments MSP430
8051
Motorola 6811	AS11 ASM11		AS11
PIC		GPASM	GPASM

^[s] source code only

C compilers

target CPU/OS	host OS
	DOS	Win32	x86 Linux
16-bit x86/DOS	Turbo C 2.01, Turbo C++ 1.01 Micro C Dev86-DOS Pacific C Watcom C		Dev86
32-bit x86/DOS	DJGPP (GCC) Watcom C
32-bit x86/Win32		CygWin (GCC) MinGW32 (GCC) Borland C++ 5.5 LCC-Win32
680x0	GCC		GCC
ColdFire
PowerPC		GCC	GCC
ARM	GCC (a.out)	GCC	GCC
MIPS		GCC	GCC
SuperH
H8		GCC	GCC
AVR		GCC GCC	GCC
MSP430		GCC
8051	Keil 8051 C^[e]	Raisonance^[e] SDCC	SDCC
6811	Image Craft v0.50	GCC	GCC
PIC
Z-80		GameBoy Development Kit SDCC	GameBoy Development Kit SDCC
Siemens/Infineon C166/167		GCC	GCC

^[e] limited evaluation version

debuggers

target CPU/OS	host OS
	DOS	Win32	x86 Linux
16-bit x86/DOS
32-bit x86/DOS	FSDB (part of GDB package) RHIDE (DOS IDE with GDB front-end; similar to Borland)
32-bit x86/Win32		Turbo Debugger OllyDebug
680x0
ColdFire
PowerPC
ARM
MIPS
SuperH
H8
AVR
MSP430		NoICE
8051		NoICE
6811		NoICE
PIC
Z-80		NoICE

CPU simulators

target CPU/OS	host OS
	DOS	Win32	x86 Linux
x86		Bochs (simulates entire PC)	Bochs (simulates entire PC)
680x0		WISM68
ColdFire
PowerPC
ARM
MIPS
SuperH
H8
AVR
MSP430
8051	S51^[s]		S51^[s]
6811		Sim68xx	Sim68xx
PIC

^[s] source code only

x86 locators

target CPU/OS	host OS
	DOS	Win32	x86 Linux
16-bit DOS	EXEHEX and ROMIZE John Fine's JLOC LOCATE.EXE tc2prom Borland ROM Kit

tiny (resident) BASIC

for x86 processors
for 680x0 processors
for 8051 processors
- Intel MCS-51 BASIC (source code)
- Other 8052 BASICs and code from Steve Quest
- 8052 BASIC info from Lakeview Research
for 6811 processors
for AVR processors
for PIC processors

tiny (resident) Forth

for x86 processors
for 680x0 processors
for 8051 processors
for 6811 processors
for AVR processors
for PIC processors