System information

x xy long$name
x: yxl: longer$naned$data:
X1Y2 X1x2 x234$5678$9012$3456:
The operation field contains either an assembler directive or pseudo operation, or an 8080
machine operation code. The pseudo operations and machine operation codes are described in
Section 3.3.
Generally, the operand field of the statement contains an expression formed out of constants and
labels, along with arithmetic and logical operations on these elements. Again, the complete
details of properly formed expressions are given in Section 3.3.
The comment field contains arbitrary characters following the semicolon symbol untill the next
real or logical end-of-line. These characters are read, listed, and otherwise ignored by the
assembler. The CP/M assembler also treats statements that begin with an * in column one as
comment statements that are listed and ignored in the assembly process.
The assembly-language program is formulated as a sequence of statements of the above form,
terminated by an optional END statement. All statements following the END are ignored by the
assembler.
3.3 Forming the Operand
To describe the operation codes and pseudo operations completely, it is necessary first to present
the form of the operand field, since it is used in nearly all statements. Expressions in the operand
field consist of simple operands, labels, constants, and reserved words, combined in properly
formed subexpressions by arithmetic and logical operators. The expression computation is
carried out by the assembler as the assembly proceeds. Each expression must produce a 16-bit
value during the assembly. Further, the number of significant digits in the result must not exceed
the intended use. If an expression is to be used in a byte move immediate instruction, the most
significant 8 bits of the expression must be zero. The restriction on the expression significance is
given with the individual instructions.
3.1 Introduction CP/M Operating System Manual
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