Digital Channel Display Format
The FCC require digital channel numbers expressed by integer+decimal point(.)+integer. Example (see above image): 123.1 mean a program is transmitted on
channel 123, subchannel 1 (usually, but not necessarily so, this channel is transmitting the analog program on channel 123 ).
On some equipment the decimal point is replaced with a hyphen (-) e.g. 123-1. This technology is called Multicast and it
allows the broadcaster to simultaneously transmit a few different programs on one channel.
Analog Channel Display Format
Analog channels (non digital programs) expressed in integers without decimal point (.) or hyphen (-). Analog channels transmit only one program at a time.
Cable Operators Channels Index Numbers
The Cable operators assign INDEX numbers to their CABLE BOX channels lineup. These INDEX numbers seldomly correspond to the actual channel
number and may be different in one location to another, let alone the lineup differences between the various Cable operators.
This method allows the operators to lineup channels independently of frequeny or digital channels format numbers and it mainly serves marketing interests.
FCC / DTV.gov: