Besides compiling these voluminous works of over 2000 pages, he also proposed scientific ideas to standardise Sinhala script.
When the Nalanda College Colombo was relocated to Minuwangoda during the World War II, as a security measure, his parents took the opportunity to shift him to that school.
Some of Wijayatunga's notable classmates at Nalanda College were Karunaratne Abeysekera, Dr Hudson Silva, Hon.
Immediately after his University education, Wijayatunga joined the staff of Dharmaraja College, Kandy as a science teacher.
During the years 1984–1990, he was the Editor-in-Chief of the Sinhalese Encyclopaedia as well as the Officer-in-Charge, Sinhala version of the Legislative Enactments of Sri Lanka.
Realising that none of the two major parties in Sri Lanka would espouse the rights of Sinhalese Buddhists, which was uppermost in his mind, he established the Sinhalaye Mahasammatha Bhoomiputra Pakshaya in 1990 with a group of intellectuals.
If Dr. Harischandra Wijayatunga had contested, the outcome of the 2005 presidential election would have been more complicated due to the unpopularity of the then government and Mahinda Rajapaksa may have lost by a narrow margin resulting in the possibility of the war being dragged on further.
[7] For the 1956 General Election, Mr. S. W. R. D. Bandaranaike promised to Sinhalese Buddhists that if his party could set up the government, he would make Sinhala the only state language within 24hrs.
Months after the 1956 General Election, Prof. F. R. Jayasuriya started a fast unto death to force S. W. R. D. Bandaranaike's government to implement the promise with the support of Mr. Harischandra Wijayatunga and other extremists.
Mr. Harischandra Wijayatunga openly supported and publicly promoted the fast unto death by Prof. F. R. Jayasuriya, to force then S. W. R. D. Bandaranaike government to implement Sinhala as the only State language.
The most important result was that the Sinhalese Buddhist masses got a chance to study beyond primary education up to advanced level in Sinhala.
This effort resulted in Sinhala medium schools to produce the country's engineers, doctors, public servants, police, military and other higher positions.
In fact the use of the native language helped these countries to tap into their vast national resources, human and otherwise, for development.
He has travelled widely in many Asian, African and European countries, and was invited to address various groups of learned societies in India, Japan, UK and Australia.