Turing is a model computer. It contains all the parts that of a real computer but simplified a bit so that you can understand what the parts do when it is working.
There may be some debate about whether Turing is a computer or a CPU – we leave this decision to you, but it contains all CPU components plus a virtualised memory and I/O unit. This is MUCH simpler than even the simplest real CPU/computer but it contains all the parts that are needed. It also has some parts that are not in a real computer and we will explain these later in this section.
You can see from the diagram above that there are 4 main parts (called units) and a route that connects the units together (this is called a bus). The 4 units are: Control Unit, Arithmetic Unit (inside the Central Processing Unit), Memory Unit and the Input and Output Unit (and the buses connecting them).
Some Key points about Turing:
- All registers and locations are 8 bit and are shown in hexadecimal (H) or binary (B)
- Turing contains an accumulator and two other general purpose registers (B and C).
- Only the accumulator can carry out arithmetic.
- Turing shows flags depending on the result of an operation in the flag register
- There are 255 memory locations, each of which hold a 8 bit value.
- The memory address register shows which location in the memory block can be accessed
- The program counter contains the address in memory where the next program instruction will be taken from
- Turing has a simulated I/O unit to allow users to write programs which affect the "outside" of the CPU.
- Turing Clock records the time taken for any operation and can be reset manually.