Instruction Codes• A computer instruction is a binary code that determines the
micro-operations in a sequence for a computer.
What are Instruction Codes and Operands in
Computer Architecture?
Instruction codes are bits that instruct the computer to execute a specific operation. An
instruction comprises groups called fields. These fields include:
An instruction comprises groups called fields. These fields include:
The Operation code (Opcode) field determines the process that needs to be
performed.
The Address field contains the operand's location, i.e., register or memory location.
The Mode field specifies how the operand locates.
An instruction code is a group of bits (binary code ) that instruct the computer to perform a
specific operation.
• Each computer has its specific group of instructions.
The operation code of an instruction is a group of bits that define operations such as addition,
subtraction, shift, complement, etc.
They are saved in the memory along with the information.
• An instruction must also include one or more operands, which indicate the registers and/or
memory addresses from which data is taken or to which data is deposited.
An instruction comprises groups called fields. These fields include:
The Operation code (Opcode) field determines the process that needs to be
performed.
The Address field contains the operand's location, i.e., register or memory location.
The Mode field specifies how the operand locates.
Opcodes specify the operation for specific instructions.
An address determines the registers or the areas that can be used for that
operation. Operands are definite elements of computer instruction that show
what information is to be operated on.
It consists of 12 bits of memory that are required to define the address as the
memory includes 4096 words. The 15th bit of the instruction determines the
addressing mode (where direct addressing corresponds to 0, indirect addressing
corresponds to 1). Therefore, the instruction format includes 12 bits of address
and 1 bit for the addressing mode, 3 bits are left for Opcodes.
Basic Computer Instructions
Basic computer instructions are the elementary operations that a computer
system can perform. These instructions are typically divided into three
categories: data movement instructions, arithmetic and logic instructions,
and control instructions.
What is Data Movement Instructions?
Data movement instructions are used to move data between different parts
of the computer system. These instructions include load and store
instructions, which move data between memory and the CPU. and
input/output (I/O) instructions, which move data between the CPU and
external devices.
What is Arithmetic and Logic Instructions?
Arithmetic and logic instructions are used to perform mathematical
operations and logical operations on data stored in the system. These
instructions include add, subtract, multiply, and divide instructions, as well as
logic instructions such as AND, OR, and NOT.
What is Control Instructions?
Control instructions are used to control the flow of instructions within the
computer system. These instructions include branch instructions, which
transfer control to different parts of the program based on specified
conditions, and jump instructions, which transfer control to a specified
memory location.
The basic computer has 16-bit instruction register (IR) which can denote
either memory reference or register reference or input-output instruction.
Registers
What are Computer Registers in Computer Architecture?
Computer registers are high-speed memory storing units. It is an element of the
computer processor. It can carry any type of information including a bit
sequence or single data.
A register should be 32 bits in length for a 32-bit instruction computer. Registers
can be numbered relies upon the processor design and language rules.
The following table shows the registers and their functions.
Register Number
Register Name Function
Symbol of Bits
OUTR 8 Output register OIt holds output character.
INPR 8 Input register It holds input character.
Program It holds the address of the
PC 12
Counter instruction.
It holds an address for
AR 12 Address Register
memory.
DR 16 Data Register It holds memory operand.
AC 16 Accumulator It’s a processor register.
Register Number
Register Name Function
Symbol of Bits
Instruction
IR 16 It holds an instruction code.
Register
Temporary
TR 16 It holds temporary data.
Register
The description for each of the registers determined in the figure is as follows –
The data register holds the operand read from the memory.
The accumulator is a general-purpose register need for processing.
The instruction register holds the read memory.
The temporary data used while processing is stored in the temporary
register.
The address register holds the address of the instruction that is to be
implemented next from the memory.
The Program Counter (PC) controls the sequence of instructions to be
read. In case a branch instruction is detected, the sequential execution
does not arise. A branch execution calls for a transfer to an instruction
that is not in sequence with the instructions in the PC.
The input register (INPR) and output register (OUTPR) are the registers
used for the I/O operations. The INPR receives an 8-bit character from the
input device. It is similar to the OUTPR.
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