- octal constant
- octal dump
- octal notation
- octal representation
- octal system
- octangular
- octet
- octonary signaling
- ocular
- odd face
- odd parity
- odd symmetry
- odevity
- off-center
- off-line
- offered load
- office
- office code
- offline setup
- offset
- often
- ohmic loss
- oil
- oil can
- oil leak
- oil pump
- OLE server
- olitic lime
- omit function
- on-line
- on-stream
- ondoscope
- one page
- one-address
- one-fourth
- one-one
- oneway communication
- ok button
- OLE client
- on center
- on-hook
- on-screen
- once
- one
- one time
- one-sided
- one-way
- onelevel subroutine
- online analysis
- online communication
- online computing
- online debugging
- online diagnostics
- online dump
- online index
- online machines
- online monitor
- online operation
- online processing
- online service
- online shopping
- online storage
- online test
- online testing
- only
- only element
- online access
- online backup
- online banking
- online buddy
- online computer
- online consumers
- online control
- online debug
- online distribution
- online edit
- online help
- online layout
- online package
- online resources
- online system
- only field
- opal glass
- opaque
- opcode fetch
- open access
- open architecture
- open clutch
- open code
- open cover
- open covering
- open cycle
- open disk
- open environment
- open field
- open file
- open floor
- open formula
- open function
- open kernel