**Characters : Characters and character strings must be enclosed in single or double quotes; For example, "A" or 'hello'. Characters are translates into their ASCII codes by the assembler, so there is no difference between using "A" and 4h (the ASCII code for "A") in a program.
table 4.1 Data-Defining Pseudo-ops
Pseudo-op Stands for
DB define byte
DW define word
DD define doubleword (two consecutive words)
DQ define quadword (four consecutive words)