System information

The memory buffer appears logically as shown in Figure 2-3, where the dashes represent
characters of the source line of indefinite length, terminated by carriage return (<cr>) and
line-feed (<If>) characters, and CP represents the imaginary character pointer. Note that the CP is
always located ahead of the first character of the first line, behind the last character of the last
line, or between two characters. The current line CL is the source line that contains the CP.
Figure 2-3. Logical Organization of Memory Buffer
2.1.4 Line Numbers and ED Start-up
ED produces absolute line number prefixes that are used to reference a line or range of lines. The
absolute line number is displayed at the beginning of each line when ED is in insert mode (see
the I command in Section 2.1.5). Each line number takes the form
nnnnn:
where nnnnn is an absolute line number in the range of 1 to 65535. If the memory buffer is empty
or if the current line is at the end of the memory buffer, nnnnn appears as 5 blanks.
2.1 Introduction to ED CP/M Operating System Manual
2-5