QUES: In this paper, he described a new system for storing and working with large databases. Instead of records being stored in some sort of linked list of free-form records as in CODASYL, Codd's idea was to use a "table" of fixed-length records, with each table used for a different type of entity. A linked-list system would be very inefficient when storing "sparse" databases where some of the data for any one record could be left empty. The relational model solved this by splitting the data into a series of normalized tables (or relations), with optional elements being moved out of the main table to where they would take up room only if needed. Data may be freely inserted, deleted and edited in these tables, with the DBMS doing whatever maintenance needed to present a table view to the application/user.

What model solved the problem of databases where information was missing?
What is the answer?
ANS: relational
QUES: At the end of the last ice age, what are now the British Isles were joined to the European mainland as a mass of land extending north west from the modern-day northern coastline of France, Belgium and the Netherlands. Ice covered almost all of what is now Scotland, most of Ireland and Wales, and the hills of northern England. From 14,000 to 10,000 years ago, as the ice melted, sea levels rose separating Ireland from Great Britain and also creating the Isle of Man. About two to four millennia later, Great Britain became separated from the mainland. Britain probably became repopulated with people before the ice age ended and certainly before it became separated from the mainland. It is likely that Ireland became settled by sea after it had already become an island.

During the start of the first ice age, the British Isles were connected to which continent as a mass of land?
What is the answer?
ANS: unanswerable
QUES: Through-hole manufacture adds to board cost by requiring many holes to be drilled accurately, and limits the available routing area for signal traces on layers immediately below the top layer on multi-layer boards since the holes must pass through all layers to the opposite side. Once surface-mounting came into use, small-sized SMD components were used where possible, with through-hole mounting only of components unsuitably large for surface-mounting due to power requirements or mechanical limitations, or subject to mechanical stress which might damage the PCB.

What type of boards end up with limited routing space in through-hole manufacture?
What is the answer?
ANS:
multi-layer