DQ:  Define  Quad word:- 

This directive is taken in use to direct the assembler to reserve 4 words (8 bytes) of memory for the specified variable and can initialise it having the specified values.

DT: Define Ten Bytes:-

The DT directive directs the assembler to define the specified variable requiring 10- bytes for its storage and initialise the 10-bytes with the specified values. The directive may be used in case of variables facing heavy numerical calculations, normally processed by numerical processors.