X is a simple mathematical model of a computer. X has unrestricted and...
Turing machines
A Turing machine is a simple mathematical model of a computer. It is named after the mathematician Alan Turing, who first described it in 1936. A Turing machine consists of an infinite tape divided into cells, each cell holding one symbol. The machine has a read/write head that can move along the tape, reading the symbol at the current cell and writing a new symbol in its place.
Unrestricted and unlimited memory
One of the key features of a Turing machine is its unrestricted and unlimited memory. The tape of a Turing machine can be infinitely long, allowing it to store an unlimited amount of information. This makes a Turing machine more powerful than other models of computation, such as finite automata or pushdown automata, which have limited memory.
Read/Write head
The read/write head of a Turing machine is responsible for reading the symbol at the current cell and writing a new symbol in its place. It can also move left or right along the tape to access different cells. This allows the Turing machine to perform computations by manipulating the symbols on the tape.
Turing machine as the correct answer
Based on the given information, X is described as a mathematical model of a computer with unrestricted and unlimited memory, and a read/write head. This perfectly matches the characteristics of a Turing machine. Therefore, the correct answer is option 'C' - Turing machines.