Coding of information comprising contrasting properties arranged to define first and second machine-detectable code elements, said code elements being arranged in overall patterns having opposed ends, said first and second code elements being interpretable to define contrasting logic levels, each of said patterns including a start pattern of code elements, an end pattern of code elements and a plurality of code elements representing given information between said start and end patterns, pairs of said plurality of code elements comprising both a first code element and a second code element which together define either a first character or a second character depending upon the order in the pair of the first and second code elements, said start pattern and said end pattern each including an end code element at each of said opposed ends of said overall pattern, both end code elements being either first code elements or second code elements, and said start pattern of code elements and said end pattern of code elements being distinguishable from each other and from said plurality of code elements between said start pattern and said end pattern after being machine detected, said start pattern and said end pattern each including at least four code elements arranged such that three consecutive code elements of the same logic level do not occur within the start and end patterns and the plurality of code elements adjacent thereto, said code elements between said start and said end patterns being arranged so that after they are machine detected said given information may be obtained from them.