The .db and .byte statements are used to define a series of 8 bit data byte values. The values must be in the range 0 to 255. The .db keyword will also convert an ASCII string into a sequence of binary values
        [<label>] .db   <expr> [, <expr> [, <expr> ...]]
        [<label>] .byte <expr> [, <expr> [, <expr> ...]]
                .db     1,2,3
                .db     "hello world",0

MSG_START       .db     MSG_END - (MSG_START + 1)
                .db     "another message"

BEWARE: defining bytes in the code section of a CPU that has a program counter that counts in words may cause the location counter to be incremented to an odd address. Also note that the length of a block of data will be reported as half the expected size. This will not affect the data stored, just the observed length.