O2
Oaklisp
OBE
Oberon
Oberon-1
Oberon-2
Oberon-V
OBJ
OBJ0
OBJT
OBJ1
OBJ2
OBJ3
Object CHILL
Object LISP
ObjectLOGO
Object Oberon
Object-CHILL
Object-COBOL
Object-Oriented Turing
ObjectPAL
Object Pascal
Object REXX
Object Star
ObjectVIEW
Object-Z
Objective C
Objective CAML
Objective VHDL
Objlog
ObjVlisp
ObjVProlog
Obliq
Oblog[1]
OBLOG[2]
OBSCURE
Obtuse
Oc
OCAL
OCALA
occam 1
occam 2
occam 3
OCL
OCODE
Octave
odl[1]
ODL[2]
ODL
ODL[3]
ODL[4]
OGL
OIDL
OIL[1]
OIL[2]
OISC
OLC
OLDAS
OLGA
Omega
OML[1]
OML[2]
OML[3]
OMNI
OMNICODE
OMNIFAX
Omnimark
OMNITAB
OMT
Ondine
Ontic
OO-CHILL
OODL
OOF
OOGL
OOPS
OOT
OOZE
OPAL-0
OPAL[1]
OPAL[2]
OPAL[3]
OPAL[4]
OPAL[5]
OPL
OPL[2]
O-plan
OPS[1]
OPS[2]
OPTRAN
Opus
OQL
Orca
OREGANO
Orient84/K
ORTHOCARTAN
Orwell
Orthogonal
OSCAR[1]
OSCAR[2]
OSL
O'small
OSQL
OSSL
Ottawa Euclid
OWHY
OWL
Ox
Oz
oz++