On April 23, 1913, the International Telecommunications Union assigned Canada the call letter range from VAA to VGZ. These calls have never been used for regular broadcast stations, but other radio services have been given call signs in this range (for example, Canadian amateurs use VE... calls.)
Beginning in 1922 and for several decades, Canadian radio (and later, TV stations) were assigned call letters (or call signs) beginning with CF-, CH-, CJ-, CK-, or 10-, followed by two letters which would be exclusive to one station. (exceptions: CKY Winnipeg and CKX Brandon licensed to the Manitoba Government Telephones). Note that CG- and CI- were not used; however in the 1960s with the proliferation of FM and TV stations, CI calls were then issued. (The "10" stations (eg 10AB) were not licensed to broadcast commercials, but were reserved for what were termed "Amateur Radio Stations" transmitting on the regular broadcast band. These were mostly operated by community groups or experimenters. It was an inexpensive way to get into radio - the license fee was $ 25 as opposed to $ 50 for the commercial station. All but one of these stations, coincidentally there were 10 of them, ultimately obtained commercial licenses, and by 1935 all the "10" call signs had disappeared from the spectrum.)
In 1929 new international allocations were made, and the assignment of CFA- to CKZ- to Canada became officially recognized.
An exception was also made in the case of the Canadian National Railways three owned-and operated stations and the CNR's "phantom Stations" (the latter used only when time was leased by the CNR on privately-owned stations). Thus, the owned stations became identified as CNRA Moncton, CNRO Ottawa and CNRV Vancouver. (Internationally, CN- calls are supposed to be reserved to Morocco, but no protest seems to have been lodged.)
When the Canadian Radio Broadcasting Commission took over the CNR stations in 1932 and CRBC began to buy some of the existing private stations, the prefix "CRC" was reserved for its exclusive use (examples - CRCT (formerly CKGW) Toronto, CRCY (formerly CKNC) Toronto; etc. (Internationally, CR- calls were supposed to be reserved to Portugal — now assigned to various former Portuguese colonies — but no protest seems to have been lodged.)
On succeeding the CRBC in 1936, The Canadian Broadcasting Corporation reserved for itself the prefix "CB". CRCT became "CBL" Toronto - the "L" because of its location in the Great Lakes region; CRCY became "CBY". As the CBC began to build its powerful 50 kW transmitters, the station calls usually related to their region or purpose, CBF Montreal - French language, CBK Watrous, Saskatewan, in honor of Kelsey the explorer CBE Edmonton, CBH Halifax, etc. (Internationally, CB- calls are supposed to be reserved to Chile, but no protest seems to have been lodged.)
Before Newfoundland became Canada's 10th province in 1949, the call sign VO-was allocated to the island. Three stations began operating in St. John's - VOCM, VOAR and VOWN and these identifications were "grandfathered" in when Newfoundland entered Confederation, however, stations licensed since were given call signs similar to the rest of Canada. (Note that prior to this time there were other VO- calls licensed in Newfoundland, but these stations had been closed before Newfoundland became a province of Canada.)