ZiLOG Z80 Handbook page 135

started by any character and is encountered by the same character.
It is convenient to use unusual characters as the delimiters.
0100 43555253 TXT $CURSE YOU RED BARON$
0104 4520594F
010B 55205245 Delimiter
010C 44204241
0120 524F4E00
0124
The pseudo -ops above are some of the most commonly seen and
will be used in the examples of Section II. The actual pseudo-ops
used in Z-80 microcomputers software will vary, however , and the
reader must refer to the manufacturer 's literature for the mnemonics
and formats used.
ASSEMBLY MECHANICS
Once a program has been written, the actual assembly mechanics
are quite easy. The source statements are entered via the keyboard
and a copy of the source lines is recorded on some type of I/O
medium such as paper tape, magnetic tape, or floppy disc. In many
cases, a utility program called an editor is used to transfer the key-
board input to the storage medium. After the program has been
copied onto the medium, the assembler is loaded into the micro-
computer if a resident assembler is being used, or into the host com-
puter if a cross-assembler is employed. The assembler will then read
the source from the storage medium for the first pass. If paper- or
magnetic-tape cassettes are used as the storage medium, the paper
tape or cassette may then have to be repositioned manually to the
start of the source image; in other cases, the system will automati-
cally restart from the beginning of the input medium. The assembler
then executes the second pass producing a listing such as the one
shown in Fig. 9-3 and an object module. The object module is essen-
tially the machine-language code in a special loader format. The
object module may physically be paper tape, magnetic tape, or
floppy disc. The object module output of the assembler can now be
loaded into microcomputer memory by the loader utility program
and, after the load, be available for execution.
As previously mentioned, few programs run the very first time,
and subsequent reassemblies, loads, and executions will undoubtedly
have to be performed until a final version is produced. For each
iteration (and in some systems there are dozens), the assembler
greatly simplifies the coding process.
144