ASA carriage control characters

ASA control characters are simple printing command characters used to control the movement of paper through line printers. These commands are presented as special characters in the first column of each text line to be printed, and affect how the paper is advanced before the line is printed.

"ASA" is the abbreviation of the American Standards Association, a former name for the American National Standards Institute (ANSI), which has standardized these control characters in ANSI X3.78-1981(R1992) representation of vertical carriage positioning characters in information interchange. These are also called "FORTRAN control characters" because they first appeared in versions of FORTRAN II in the early 1960s,[1] although they have since been used by other programming languages such as COBOL and PL/I.

Operation

ASA Character Action ASCII Equivalent
blank Advance 1 line (single spacing) CR LF
1 Advance to next page (form feed) CR FF
2–9, A, B, C Advance to vertical tab stop CR VT (approximately)
0 Advance 2 lines (double spacing) CR LF LF
- Advance 3 lines (triple spacing) CR LF LF LF
+ Do not advance any lines before printing,
overstrike previous line with current line		 CR

Overstriking can be used to make boldface text by printing the same line twice without advancing the paper. It can also be used to make underlined text by printing a line of underscore characters atop the text.

Mainframe printers originally had a Carriage control tape, with 12 channels (1 through 9 and A through C) that can be assigned a fixed position on the page by punching a hole, allowing the printer to skip a variable distance down the page to a fixed location. Newer printers such as the IBM 4248 have done away with the physical tape and use a Forms Control Buffer (FCB) containing an image of the tape data. Normally only channel 1 is preassigned, to the top of the page.

ASA carriage control characters are still used for printer output from mainframe applications and software today, and are not limited to seasoned software or applications dating from the days of the line printer. ASA carriage control characters are interpreted by other software before being printed on modern computer printers.

Example output containing ASA carriage control characters:

1This is the first line on the page
0This is the third line on the page
-This is the 6th line on the page
 This is the 7th line on the page
+____    the                      - Overstrike the 7th line

Example as printed output:

This is the first line on the page

This is the third line on the page


This is the 6th line on the page
This is the 7th line on the page - Overstrike the 7th line

See also

References

  1. ↑ IBM Corporation (1964). Fortran Specifications and Operating Procedures IBM 1401 (PDF). p. 18. Retrieved August 18, 2016.

External links

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