The IIGS has a multitude of programming environments ranging from assembly, C, Pascal and even enhanced versions of Applesoft BASIC, as well as resource editors.
3D Logo
Apple GSBasic
Beagle Compiler v2.6
Call Box v2.0
Complete Pascal (was TML Pascal)
Design Master v2.0
Foundation v1.02
Genesys
GNO/ME
GSBasic
Hyperlogo
Iconix
Integer BASIC
Lisa816.v5.433
LogoWriter GS
MD BASIC
Merlin 16+ v4.08
Micol Advanced Basic
ORCA C
ORCA Debugger
ORCA Disassembler
ORCA Integer BASIC
ORCA M v2.0
ORCA Pascal v2.0
RADE
Sonix
Spectra Graphix 256
Talking Tools
TML Basic