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Shaadi.com Matrimonials
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PC Setup and Maintenance - Page 1
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Instruction
An instruction is an order for the computer to certain specify
functions. It may be an order for computer to read data item through for
computer to read data item through output unit.
On the other hand , an instruction may specify an arithmetic operation
such as addition subtraction multiplication and division of two numbers.
Other instruction transfer data and based of these comparisons, computer
is capable of taking decisions. The internal computer’s instruction may
perform one of the following functions.
1. Read data from input devices and write through output devices.
2. Perform arithmetic operation on data item.
3. Move data entirely within the computer.
4. Compare data item for taking logical operations.
Before a computer is able to execute an instruction, it may be stored in
the main memory of the computer even if an instruction is held in the
external memory it has to be brought to the main memory. Before
execution, thus instruction can be executed only from the main memory
and data under current processing must also be placed in the main memory
before this data can be processed.
An instruction is stored in the computer main memory as a certain
specified number of bits representing an instruction depend upon the
word size of computer.
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Instruction and data word
A computer is capable of strong instructions as well as data
in its main memory. The computer word storing an instruction is called
an instruction word and the computer word storing a data. A data item is
called data word. Instruction data are stored in computer memory as
group of binary more over a computer doesn’t differentiate between an
instruction and data item which places an addition responsibility on the
programmer to arrange story of manner may it doesn’t create a confusion
for a computer.
Instruction code and format
It consists of a fixed number of bits stored as computer
words if an instruction had “n” bits then these bits positions are
divided into two or more sections called fields. One field ( a group of
bits position in a computer word ) in an instruction has to be
performed. This field is essential because, in its absence, the
instruction becomes meaningless. The OP code may strut the computer to
add two number or compare the number or it may direct the computer to
stop the execution of the program. The remaining part the instructions
word may be divided into one or more part each part containing addresses
of a particular memory location. Thus an instruction in machine language
consist of a two part :-
1. OP CODE – Operation code.
2. Address an Address of one or more memory location for opened.
OP CODE
It’s of an instruction consist of a group of bits that define
certain arithmetic operation such as division. The number of bits
required for OP code, depends the total number of operations to be
performed by the computer. If the OP code has “n” bits. Then it is
capable of doing (2)n operations. The OP code is part of computer
instructions to tell the computer to carry out a specific operations to
such as to add two numbers. The control unit fetch an instruction from
the memory and decodes the OP codes part of it. This control unit then
issues a sequence of control signal that perform certain operations on
the data stored in the internal register.
The operation performed in internal registers are called micro
operations. Thus the operation stated in OP code is a micro operations.
Addresses
The OP codes of the instruction specified the operation to be
the performed on data or on the set of data, the instruction must tell
where the data stored. The data may stored in a register or in a memory
location. The data on which operation is to be performed is called
operand.
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Thus, the instruction must specify the operation to be performed more
over a computer program. Consist of a set of instructions. The computer
instruction must also tell explicitly or implicitly the memory.
Thus a computer’s instruction contains the following information :-
1. Operation to be operands.
2. Address or the addresses of memory locations containing the operand
or operands.
3. Address of memory locations which is to store the result.
4. Address of memory locations containing the instruction to be executed
next.
Processor
The instruction given in a program are interpreted and
carried out by the processing unit of computer. Processors are designed
to interpret the set of instruction set for the processor. Before
understanding how a processor operates, we must first understand its
architecture. Following sections 2.5.1 and 2.5.2 explain the
architecture of a processor of a hypothetical computer.
2.51 – Computer register
Broadly the CPU of a computer is divided into three
sections. The control unit, the ALU and the main memory. Computer
instructions are stored in conceptive memory locations and are executed
sequentially one at a time. The control unit reads an instruction from
specific address in memory and execute it then it reads the next
instructions in sequence and execute it and so on. After the execution
of current instruction, the address of next register. A register is a
group of flip-flops where each flip-flop is capable of storing one bit
of information. Also a register is required in central unit for storing
the instructions- code after it is read from memory. The processor
registers are required for manipulating data and a register for holding
memory address. These requirements dictate the following register.
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