Roland Barthes

Barthes's analysis is influenced by the structuralist linguistics of Ferdinand de Saussure; both Barthes and Saussure aim to explore and demystify the link between a sign and its meaning. But, Barthes moves beyond structuralism in that he criticises the propensity of narratology to establish the overall system out of which all individual narratives are created, which makes the text lose its specificity différance. Barthes uses five specific "codes" that thematically, semiotically, and otherwise make a literary text reflect structures that are interwoven, but not in a definite way that closes the meaning of the text. Therefore, Barthes insists on the (different degrees of) plurality of a text - a plurality that should not be reduced by any privileged interpretation. Barthes also flags the way in which the reader is an active producer of interpretations of the text, rather than a passive consumer.
Barthes defines five codes that define a network (or a topos) that form a space of meaning that the text runs through. But, these codes and their mutual relations are not clear structures, because it would close the multivariance of the text. Thus, Barthes defines the code in a vague way: Each of the units of the text marks a virtual digression toward a catalogue of other units. Each code also appears as voices that altogether weave the text, though each of them for a while may dominate the text.
Two of the codes are sequential and structure the text in an irreversible way The hermeneutic code denotes an enigma that moves the narrative forward; it sets up delays and obstacles that maintain suspense. The proairetic (ACT) code organises (small) intertwined sequences of behaviors. Each such sequence has its own regularity that does not follow the logic of the narrative (though it is used in it).
The rest of the codes are reversible. The two of them structure the text: The semic code (SEM) designates a special kind of signifiers (e.g. person, a place, an object) to which adhere unstable meanings and that enable the development of a theme through the story.The symbolic code (SYM) are meanings that are constitutive (stemming from the fields of rhetoric, sexuality, or economy), but cannot be represented in the text, except in metonymies, which renders the text open to different interpretations.
The last code refers to meanings that are external to the text: The cultural code is the references to science or wisdom (sagesse).
Barthes does not provide an overall structure for how the codes are integrated because he wants to preserve the plurality (multivalence) of the text. Since reading is plural, a different reader might invoke the codes differently and combine them differently ending up with a different understanding. Moreover, whereas the classical text tends to enforce a particular model of integrating the codes, the modern plural text does not.