Cable knit cardigans can be found in many clothing stores. Some specific ones may include Mexx, Old Navy, or The Bay. If you are having trouble finding a cable knit cardigan, you can always ask employees for help locating specific products.
You can find out if cable knit cardigans are in style from websites that follow fashion such as eZine. As of May, 2013, cable knit cardigans are in style.
The best place for finding patterns for whatever knitting project one might have it a site called KnittingHelp. On this site you can find tips and patterns for both human projects and animal knitting.
Cable knit tights are used to protect and keep the legs warm. Cable knit tights are usually worn during the colder months such as during winter in order to retain body heat.
C4B means "cable four back" and is a cable worked over four stitches. Assuming you knit from right to left you place two stitches on your cable needle (or another temporary stitch holder), hold it behind your work, knit two stitches and then knit the two stitches you placed on the cable needle.
I think you may be referrnig to cable knitting - use a cable needle.
C2B = Cable 2 back. C2F = Cable 2 front. Usually you will find the definitions for knitting abbreviations in the header section of your pattern. Although these two abbreviations are fairly common they are often used for different types of cable depending on the design of the garment. C2B could mean "slip the next two stitches onto a cable needle and hold at the back, knit the next two stitches on the left hand needle and then knit the two stitches on the cable needle." Or it could mean "slip the next two stitches onto a cable needle and hold at the back, knit the next stitch on the left hand needle and then knit the two stitches on the cable needle." Or it could mean "slip the next stitch onto a cable needle and hold at the back, knit the next stitch on the left hand needle and then knit the stitch on the cable needle." Your best bet is to check the pattern to find the definition used by the designer. Please note: The general accepted abbreviation C2B (Cross 2 Back) and C2F (Cross 2 Front) are generally formed using method 2 above (i.e., "slip the next two stitches onto a cable needle and hold at the back, knit the next stitch on the left hand needle and then knit the two stitches on the cable needle.").
There are many retailers that sell cable knit sweaters both in store and online. One can purchase them from Amazon, Macy's, Polyvore, Forever 21 and Walmart.