Tutor profile: Vincenzo V.
Subject: Computer Science (General)
What is the Von Neumann model?
The Von Neumann model is an abstract model a programmable computer; it consists of 4 main components: central processor, main memory, i/o interfaces, and buses, which link them all together. In the Von Neumann model the main memory contains both the data and the instructions that are ment to operate on that data. Having the instruction in memory is what makes the computer "programmable" as opposed to previous machines in which the program was fixed by the hardware configuration (for instance the traditional calculator).
Subject: Computer Networking
What is the advantage of the "layered" paradigm in computer networking?
Splitting networking functions in a stack of layers allows to subdivide the problem in smaller, easier sub-problems that can be solved separately. Each layer act as a user of the layers immediately below and as a provider of services for the layer immediately above. As long as the interface is defined and the service is provided as expected, there is no need for layers higher up in the stack to worry about the nitty-gritty details of the lower layers; conversely, lower layers can take care of providing their services without worrying about how in detail those services will be used. Layer implementations can even be swapped with equivalent ones out in a mostly transparent way without affecting other layers, for instance the exact same applications can run over wired ethernet or WiFi.
Subject: C Programming
Suppose you have a variable declared and defined with the following syntax int X; What is the type of that variable? What type does the expression X evaluate to?
The variable X is an array of integers: in the declaration, X is the name, int the type. The expression X has type int, since it represents the 21st element of the array X; however the array X was only defined to have 20 elements, so the use of this expression, albeit vaild in syntax, represents a logical error.
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