An introduction to capabilities of the HP Printer Control Language

• The PCL language employs some special sequences of ASCII control-codes, known as ‘escape’ sequences (since they begin with the code for the escape-key: 0x1B)
• The character-sequence ‘\e’ may be used to generate this special non-printable byte
• The punctuation-symbols, numerals, and alphabetic characters that follow specify a specific command to the HP laser printer

• An application that wishes to do printing can create a textfile containing a mixture of document text and PCL commands
• This text file is then ‘submitted’ to the printer using a Linux command (e.g., ‘lpr’)
• The printer recognizes commands by the occurrence of an ‘escape’ code

• Printer initialization command has format:
ESC E
• Example: fprintf( prn, “\eE” );
// This statement writes the initialization
// command to a file whose file-pointer is
// the ‘prn’ variable

• Setting print resolution for raster graphics is done with the following command:
ESC * t # R
• Here the ‘#’ symbol denotes a numeric parameter that specifies the number of dots-per-inch (i.e., the pixel resolution)
• Possible choices are: 75, 100, 150, 300

• Set the cursor’s Y-coordinate:
ESC * p # Y
• Set the cursor’s X-coordinate:
ESC * p # X
• Example: If dots-per-inch equals 300, then fprintf( prn, “\e*p%dY\e*p%dX”, 150, 150 ); places the cursor a half-inch from margins

• Here is the command that specifies the type of raster data-compression used:
ESC * b # M
• The possible numeric parameters are:
– 0: unencoded (no compression)
– 1: run-length encoding
– 2: tagged image file format (TIFF)
– 3: delta row compression

• The printer’s default mode is ‘text’ mode
• To switch into raster graphics mode, the following command is issued:
ESC * r # A
• Here the ‘#’ symbol specifies the type of cursor-positioning that is used:
– 1 means use current cursor position
– 0 means use the printer’s left margin

• Here is the command for sending raster graphics data to the printer:
ESC * b # W
• Here the ‘#’ symbol stands for a numeric parameter that specifies the number of bytes of raster data that follows the ‘W’
• Then the cursor moves to the next row

• To exit from raster graphics mode, the following command is used:
ESC * r B
• This command switches the printer back to its normal ‘text’ mode, and it is issued after the final row of raster graphics data is sent

• The PCL language is ‘page oriented’, and once a page’s description is complete, the printer should eject that page
• The ‘form-feed’ command ‘\f’ can be sent to the printer to eject the completed page: fprintf( prn, “\f” );

• We have posted an application program that prints certain Waveform Audio files, using the printer’s PCL raster graphics commands
• So far it only works with 8-bit non-stereo data-format
• To avoid wasting paper and toner, it only prints the first page of the waveform