The South African Identity Number of the 1970s and 80s enshrined the Apartheid era ideal of racial registration. It was brought in to effect by the 1950 Population Registration Act which identified four different racial groups: White, Coloured, Bantu (Black) and others. Over the next two decades the racial classification of both the Coloured and 'other' groups were extended until, by the early 80s there was a total of nine different racial groups being identified.
Over the same period, the Apartheid government introduced legislation creating 'independent' homelands for Blacks, effectively making them 'aliens' in their own country. The initial legislation for this actually dated back to before the introduction of Apartheid - the 1913 Black (or Natives) Land Act, which had created 'reserves' in the Transvaal, Orange Free State and Natal provinces. The Cape province was excluded because Blacks still had a limited franchise (entrenched in the South Africa Act which created the Union) and which required a two-thirds majority in parliament to remove. Seven percent of the land area of South Africa was dedicated to roughly 67% of the population.
With the 1951 Bantu Authorities Act the Apartheid government lead the way for the establishment of territorial authorities in the reserves. The 1963 Transkei Constitution Act gave the first of the reserves self-government; and with the 1970 Bantu Homelands Citizenship Actand 1971 Bantu Homelands Constitution Act the process was finally 'legalised'. QwaQwa was proclaimed the second self-governing territory in 1974 and two years later, through the Republic of Transkei Constitution Act, the first of the homelands became 'independent'.
By the early 80s, through the creation of independent homelands (or Bantustans), Blacks were no longer considered 'true' citizens of the Republic. The remaining citizens of South Africa were classified according to eight categories: White, Cape Coloured, Malay, Griqua, Chinese, Indian, Other Asian, and Other Coloured.
The South African Identity Number was 13 digits long. The first six digits gave the birth date of the holder (year, month, and date). The next four digits acted as a serial number to distinguish people born on the same day, and to differentiate between the sexes: digits 0000 to 4999 were for females, 5000 to 9999 for males. The eleventh digit indicated whether the holder was a SA citizen (0) or not (1) - the latter for foreigners who had rights of residency. The penultimate digit recorded race, according to the above list - from Whites (0) to Other Coloured (7). The final digit of the ID number was an arithmetical control (like the last digit on ISBN numbers).
The racial criteria for identity numbers was removed by the 1986 Identification Act (which also repealed the 1952 Blacks (Abolition of Passes and Co-ordination of Documents) Act, otherwise known as the Pass Law) whilst the 1986 Restoration of South African Citizenship Act returned citizenship rights to its Black population.