There are several types of Code 128 barcodes.
The barcode is based on either or a combination of 3 tables, Table A, Table B & Table C.
Each table contains 106 characters.
Table A & Table B are very similar.
Table A has upper case characters, numbers & special characters.
Table B has upper & lower case characters, numbers & some special characters.
Table C has number pairs. eg. 00, 01, 02, 03, ....98, 99. Using number pairs Table C can compresses the barcode if it contains some numbers.

It has recently come to my attention that the Code 128 barcode I have been recommending does not work correctly for Table C characters.
The code did not like numbers containing double zeros.
I did not write this code but I have looked at the code and now modified it and added some comments to the code.
I cannot guarantee that the code works in all circumstances.
If you discover and error please let me know.

A barcode only using Table A is known as Code128A, similaly for Tables B & C.
An optimised version uses a combination of all 3 tables to keep the barcode short.
The example supplied here creates an optimised barcode.

First install this font called code128.ttf that I have downloaded from http://grandzebu.net. on your computer.

Here is a CorelDraw X6 program that will create an Optimised Code128 barcode.
It is the same as CorelDraw's Code 128 barcode that is not an EAN-128 type, does not ignore brackets and does not ignore spaces as in CorelDraw's Advanced settings.