Operational Overview Of CPU




Any processing executed by central processing unit is directed by the instruction. The processing required for a single instruction is called an instruction cycle. The four steps which the CPU carries out for each machine language instruction are fetch, decode, execute, and store (Fig. 1.6).

Operational Overview Of CPU

The steps involved in the instruction cycle while executing a program are described below. The Program Counter (PC) is the register that keeps track of what instruction has to be executed next. At the first step, the instruction is fetched from main memory and loaded into Instruction Register (IR), whose address is specified by PC register. Immediately the PC is incremented so that it points to the next instruction in the program. Once in IR, the instruction is decoded to determine the actions needed for its execution. The control unit then issues the sequence of control signals that enables execution of the instruction. Data needed to be processed by the instructions are either fetched from a register from RAM through an address register. The result of the instruction is stored (written) to either a register or a memory location. The next instruction of a program will follow the same steps. This will continue until there is no more instruction in the program or the computer is turned off, some sort of unrecoverable error occurs.

Note:

Topics You May Be Interested In
Evolution Of The Computer- A Brief History Primary Memory
Classification Of Computers Primary Memory
Computer Fundamentals And Programming In C Microprocessor
Mainframe Computer Two's Compliment
Conversion Of A Decimal Number To Its Octal Equivalent And Gate

A register is a single, permanent storage location within the CPU used for a particular, de?ned purpose. CPU contains several important registers such as

  • The program counter(PC) register holds the address of the current instruction being executed.
  •  The instruction register (IR) holds the actual instruction being executed currently by the computer. To access data in memory, CPU makes use of two internal registers:
  •  The memory address register (MAR) holds the address of a memory location.
  • The memory data register (MDR), sometimes known as the memory buffer register, will hold a data value that is being stored to or retrieved from the memory location currently addressed by the memory address register.


Frequently Asked Questions

+
Ans: An operating system may be defined as a system software which acts as an intermediary between the user and the hardware. view more..
+
Ans: There are different types of memories with particular functions. view more..
+
Ans: A computer can accept input, process or store data, and produce output according to a set of instructions which are fed into it. view more..
+
Ans: The processing required for a single instruction is called an instruction cycle. view more..
+
Ans: A number system defines a set of values used to represent quantity. view more..
+
Ans: The base, or radix, of any number system is determined by the number of digit symbols in the system. view more..
+
Ans: C stands out among general-purpose programming languages for its unrivaled mix of portability,power,flexibility and elegance.The language has block structures,stand-alone functions,a compact set of keywords,and very few restrictions. view more..
+
Ans: A computer is 'an automatic electronic apparatus for making calculations or controlling operations that are expressible in numerical or logical terms'. view more..
+
Ans: Most designs of computers today are based on concepts developed by John von Neumann and are referred to as the von Neumann architecture. Computers can be classified in variety of ways on the basis of various parameters such as usage, cost, size, processing power, and so on. The classification of computers is presented below based on their power and their use. view more..
+
Ans: Supercomputer is the most expensive and fastest type of computer that performs at or near the currently highest operational rate for computers. A Cray supercomputer is a typical example. These are employed for specialized applications that require immense amounts of mathematical calculations such as weather forecasting, nuclear energy research, and petroleum exploration etc. view more..
+
Ans: A mainframe computer supports a vast number of users to work simultaneously and remotely. Apart from providing multi-user facility, it can process large amounts of data at very high speeds and support many input, output and auxiliary storage devices. These computers are very large in size, and expensive. The main difference between a supercomputer and a mainframe is that a supercomputer can execute a single program faster than a mainframe, whereas a mainframe uses its power to execute many programs concurrently. view more..
+
Ans: A number system defines a set of values used to represent quantity. For example, the number of mobile phones kept in a shop, the number of persons standing in a queue, and the number of students attending a class. view more..
+
Ans: The base, or radix, of any number system is determined by the number of digit symbols in the system. For example, binary is a base-2 number system since it uses two symbols and decimal is a base-10 system since it uses ten symbols. view more..
+
Ans: Most people today use decimal representation to count. This number system uses TEN different symbols to represent values. In the decimal system there are 10 digit symbols 0, 1, 2, 3, 4, 5, 6, 7, 8, and 9 with 0 having the least value and 9 having the greatest value. For a number represented in decimal system, the digit on the extreme left has the greatest value, whereas the digit on the extreme right has the least value. view more..
+
Ans: Table 2.1 Number systems, bases, and symbols Number system Base Digital symbols Binary 2 0, 1 Ternary 3 0, 1, 2 Quaternary 4 0, 1, 2, 3 Quinary 5 0, 1, 2, 3, 4 Octal 8 0, 1, 2, 3, 4, 5, 6, 7 Decimal 10 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 Duodecimal 12 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, A, B Hexadecimal 16 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, A, B, C, D, E, F Vigesimal 20 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, A, B, C, D, E, F, G, H, I, J view more..
+
Ans: To convert a hexadecimal to decimal, begin by multiplying each of the hexadecimal digits by their positional weight values as expressed in decimal. Then the resulting values are added to obtain the value of the decimal number. view more..
+
Ans: To convert from decimal whole numbers to octal, the systematic approach called the repeated-division-by-8 method is used. This method is explained by the following Converting (359)10 to octal. (a) Divide the decimal number by eight and obtain a quotient and a remainder. (b) Divide the quotient by eight and obtain a new quotient and a remainder. (c) Repeat step (b) until the quotient is equal to zero (0). (d) The first remainder produced is the LSB in the octal number and the last remainder (R) is the MSB. Accordingly, the octal number is then written (from left to right) with the MSB occurring first. view more..
+
Ans: To express the value of a given octal number as its decimal equivalent, add the octal digits after each digit has been multiplied by its associated weight. view more..




Rating - 3/5
533 views

Advertisements