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Chapter 9 Writing Machine Language Instructions and Directive Statements
9.2.1
Writing Label Field
Labels are called both symbols and names. The assembler assigns a label the value of the location
counter at the point it is defined.
Coding rules
Labels can use upper-case and lower-case letters, digits, underscores (_).
Labels are coded in the first column.
The first character of a label must not be a digit.
Labels are case sensitive.
The same label name cannot be defined twice.
When the label is omitted, it must be replaced with at least one space or tab.
Terminology:
Coding examples
LABEL
LONGLABELLONGLABELLONGLABELLONGLAB
main
start_cont
The following examples are incorrect.
1LABEL
@START
START
148 Instruction Statement Fields
* Column
This is a column on the display or printer paper. One character takes one
column. Columns are counted from the left as column 1, 2, etc.
; Starts with a digit
; Uses a prohibited character
; Does not start from the first column
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