Practical Sheet 11 IAS Computer Flashcards
What are the three key concepts of von Neumann architecture?
First: the computer will have to perform the elementary operations of arithmetic most frequently. These are addition, subtraction, multiplication, and division. It is therefore reasonable that should contain specialized organs for just these operations.
Second: The logical control of the device, is the proper sequencing of its operations, can be most efficiently carried out by a central control organ.
Third: Any device that is to carry out long and complicated sequences of operations (specifically of calculations mush have a considerable memory
Single read-write memory (data and instructions)
Addressable Memory
Execution occurs in a sequential fashion (unless explicitly modified) from one instruction to the next.
What is a stored-program computer?
IAS computer, a computer that stores both data and instructions in the memory.
What are the four main components of any general-purpose computer?
Main memory, which stores both data and instructions.
Central Processing unit (CPU) and inside the CPU there is:
Arithmetic and logic unit (ALU)
Program Control unit (CC)
I/O equipment(I/O) equipment operated by the control unit
Why are registers used in CPU?
To simplify the electronics. Registers are the temporary storage for the data (bits or bytes), inside the CPU that can store the data temporarily between different components in this architecture.
What is the overall function of a processor’s control unit?
The control unit of the central processing unit regulates and integrates the operations of the computer.
Explain the use of the following registers:
a) Memory Buffer Register (MBR)
b) Memory Address Register (MAR)
c) Instruction Register (IR)
d) Instruction Buffer Register (IBR)
e) Program Counter (PC)
f) Accumulator (AC) & Multiplier Quotient (MQ)
a) Memory Buffer Register (MBR)
Contains a word to be stored in memory or sent to the I/O unit or is used to receive a word from memory or from the I/O unit.
b) Memory Address Register (MAR)
Specifies the address in memory of the word to be written from or read into other MBR.
c) Instruction Register (IR)
It decodes the opcode. Contains the 8-bit opcode instruction being executed.
d) Instruction Buffer Register (IBR)
Employed to hold temporarily the right-hand instruction form a word in memory.
e) Program Counter (PC)
Contains the address of the next instruction pair to be fetched from memory. It shows the next line of the code that should be done.
f) Accumulator (AC) & Multiplier Quotient (MQ)
Employed to hold temporarily operands and results of ALU operations. For example, the result of multiplying two 40-bit numbers is an 80-bit number; the most significant 40 bit are stored int the AC and the least significant in the MQ
What are the main two phases of instruction execution?
Fetch cycle and Execute cycle.
*8- Explain the Fetch cycle and the registers that are used in that?
Fetch cycle (reading) In the fetch cycle (reading the instruction). It has being sent from main memory MBR (Memory Buffer Register) MAR (Memory Address Register) here goes the address, and the opcode stays in the IR(Instruction Register).
Explain the Execute cycle and the registers that are used in that?
Execute Cycle (Executing) It starts from IR (instruction register) the computer understands what has to be done with the code(e.g. add, subtract) Control circuits and it sends the right signal --> signal is sent to ALU(Arithmetic and Logic Unit) add two numbers that are on the way --> MAR(Memory Address Register) will tell us where it is located.
