The computer programs are pre-accepted under Practice Note for Authorized Person and Registered Structural Engineer No. 79. Each accepted computer program will be given a unique BD reference number and a validity period of maximum 3 years. These programs are for the use by Authorized Persons , Registered Structural Engineers or Registered Geotechnical Engineers to produce calculations in support of their design submissions to the Building Authority under the Buildings Ordinance. All program users must ensure that they have obtained permission and/or license agreement from the program developers and/or distributors for use of the programs. They shall accept and understand that no warranty and liability is expressed or implied by the Building Authority on the accuracy and reliability of these programs. Should the programs prove defective, the Building Authority shall bear no responsibility for all resulting damages or losses.