View source for Marie Wocher Annotation-Speech, Writing, Code: Three Worldviews 'My Mother Was a Computer'

In the second chapter of the first part of the book, My Mother Was a Computer, Katherine Hayles focuses on the three worldviews: Speech, Writing and Code.

To explain these three different systems, she refers to Ferdinand Saussure's view of speech and Jacque Derrida's Grammatological view of writing.

The major difference between Speech/Writing and Code is, that Code in contrast to Speech/Writing is not only intended for humans , but humans and intelligent machines. Computer language is only based on two digits, from which result different logical operations. Computers have the ability to create complex structures based on a very simple basis.

To understand what the first part of Hayels book is about, you have to understand the Language model of Saussure:
The essence of his sign model is that every articulation of a word produces an imagination what forms the sign. The sign consists always of two levels: signified and signifier, concept and sound image. Every sign has its expression and its meaning. This property Saussure called bilateral.

Another property of his sign model is its arbitrariness. That context and expression of a sign for example the image (Tree) is connected to the concept Tree is not logical justified. 
But every term is based on social conventions. A sign becomes an universal validity , when the sign is accepted by the language community. Also the relation between signifier and signified shifts over time because language is a social appearance that can develop.
Saussure established three basic concepts of the language ( Hayles focuses in her book on la langue)

Language what is language as the a congenital human ability,
Langue what is language as a social phenomena and 
Parol, the concrete, physical appearance of language.

Derrida radicalises the model of Saussure. He says that the meaning of a sign not consists of the identity of signifier and signified, but because of the difference to all other signs.
No meaning is tied to a term. The significance, that we tie to the signified is the result of a process of understanding. This process of understanding is influenced by external factors as education and intelligence and differs from one person to the other. Therefor is the meaning we tie to a term always different. You actually can't even say, that you understand your vis-a-vis because everyone has another process of understanding.

Does it make sense to transfer the concept of signifier and signified onto code?
What is the signifier and what the signified in Code?
Frederick Kittler says that the signifier is the voltages and the signified, the interpretation that other layers of code give these voyages.
Programming language translate the basic mechanical level of signification into commands that are quite similar to our natural language. The translation from binary code into natural language and from natural language into binary code happens every time, when commands are interpreted or executed. Voltages functions as signifiers that interprets the commands and the command becomes the signified. The execution of the command is dependent by the ability of the machine.  code and material conditions are very close related to each other. »In the worldview of code, materiality matters«. The material constraints played a huge role by the development of computers. 

Saussure focusses on two linguistic signs that have a relation, if they are connected with each other and Derrida says that the meaning constantly changes and is indefinite.
But what about indefiniteness in code?
Binary Code can't recognise indefiniteness. The proposition of ambiguity is tenable in the world of code. For the computer, the signifier can not be meaningful without reference to a signified. In the worldview of code it makes no sense to talk about signifiers without signified. Every voltage change must have a prices significance to influence the behaviour of the machine. Without signifieds, code would would have no efficiency. All commands must be parsed as binary code to intelligible to the machine, only command that is correct can be executed. Hayles gives the example of a spelling machine, that always looks for the closest match if you type a string that is not in the dictionary.

Hayels refers to Ellen Ullmann to answer the question, if code is language. Ullmans answer is: »We can use English to invent poetry, to try to express things that are very hard to express. In programming you really can't. Finally, a computer program has only one meaning: what it does. It isn't a text for a academic to read. Its entire meaning is its function.« (Hayles, p. 47 (2005)

Code has become a very important factor in our world, because Code can regulate the conduct of Computers (every technology). 
Code has become as important as language, because it also effects things to happen. Code defines what the machine is executing. 
Code that runs on a machine is performative in a much stronger sense than that is attributed to language. Performativity is the correlation between speech and action, the connection between speech and intentionally action. Every code is automatically related to an action.