Flashcards in 3.7 Deck (57)
What are the 7 main internal components of a computer?
What is the role of the processor?
processor - takes in info and gives appropriate output. e.g. sorting & searching data, logical decision making, performing calculations, control of input & output & storage devices.
What is the role of main memory?
main memory - stores program instructions & data that are processed by the processor.
What is the role of the address bus?
address bus - specifies a physical address in main memory & the value that is to be read or written into that address is communicated via the data bus.
What is the role of data bus?
data bus - transfer data to & from the memory of a computer, or into or out of the CPU.
What is the role of control bus?
control bus - manages data processing, e.g. sends a signal to either write from the bus to a memory address or a signal to read data from a memory address.
What is the role of l/O controllers?
l/O controllers - control signals received from the processor include input(read) or output(write) requests.
These control signals are used to connect a system bus to specific l/O devices. e.g. input from keyboard & mouse with outputs to monitor & printer.
What is Von Neumann stored-program architecture?
Is based on both data & instructions stored in a single memory location, they are transmitted through a shared data bus. Is used extensively in general-purpose computing systems.
What is Harvard architecture?
Is based on the program data & instructions being stored in separate memories, instructions are fetched from instruction memory serially & data is fetched when needed by an instruction.
May be faster as the transmission of the instruction & data can take place in parallel.
Embedded systems use Harvard.
What is addressable memory?
The processor is able to address individual memory locations, so each memory location in main memory has a unique numeric code.
How does the processor allocate addresses to individual memory locations?
The processor writes numeric code into the address bus.
The processor sends request to control bus with instructions to read or write to memory location.
The data will then be transferred via the data bus.
What is the stored program concept?
Is the main memory & machine code instructions are fetched & executed serially in the processor.
Is that the program instructions & the data are both stored in memory.
What does the arithmetic logic unit (ALU) do?
Performs arithmetic & logical operations e.g. fixed point & floating arithmetic, logical operations (AND, OR, NOT, XOR, NOR, NAND) & shift operations.
Inputs are from the internal bus &the accumulator, with outputs routed to one of the registers.
What does the control unit (CU) do?
Is to fetch program instructions from memory, to decode them & to execute them serially.
What does the clock do?
System clock sends a signal to each of the computer components on a regular basis to synchronise all of the computer operations.
What is a register?
a fast memory location that exists in the processor or the l/O controller. The computer consists of general-purpose & dedicated registers.
What do general-purpose registers do?
Can be used to hold instructions & data temporarily.
Normally called R0, R1, R2.........R16
What do dedicated registers do?
used by the processor to carry out a specific role.
What are the 6 dedicated registers called?
Program counter (PC)
Memory address register (MAR)
Memory buffer register (MBR)
Status register (SR)
Current instruction register (CIR)
What is the Program counter (PC)?
Register that holds the address of the next instruction to be fetched.
What is the Memory address register (MAR)?
Holds the address of the current instruction being executed.
What is the Memory buffer register (MBR)?
Holds the instruction from the (MAR) & the associated data.
What is the Status register (SR)?
holds status of various data indicating things like: positive/negative result, carry bit used, overflow error & interrupt status.
The details of the (SR) storage are dependant upon the processor involved.
What is the Current instruction register (CIR)?
Used to store the instruction that is to be decoded & executed.
What is the Accumulator (ACC)?
Special register used at fast temporary storage by the ALU.
So basically does arithmetic calculations.
What is the Fetch-decode-execute cycle?
After the computer is turned on, fde cycle is performed. This process reads the coded program instructions in the main memory (RAM) & these instructions are then executed by the processor.
What happens in the FETCH part of the Fetch-decode-execute cycle?
1. (PC) points to next instruction to be fetched.
2. Contents of (PC) copied into (MAR).
3. The instruction in (MAR) is transferred via the data bus
to the (MBR).
4. The contents of the (MBR) are copied to (CIR) & the (PC) is updated to address next instruction.
What happens in the DECODE part of the Fetch-decode-execute cycle?
1. The instruction in the (CIR) is decoded.
What happens in the EXECUTE part of the Fetch-decode-execute cycle?
1. The decoded instruction is executed.
2. The process is repeated.