JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B.Tech II Year COMPUTER ORGANIZATION Previous Question Paper (March - 2022 - R13)

An instruction format is a template that defines the layout of bits within a machine instruction, specifying how the processor interprets the instruction. It typically consists of an opcode (operation code) field, which identifies the operation to be performed, and one or more operand fields, which specify the data or the address of the data to be processed.

The registers of a basic computer include:

• Program Counter (PC): Holds the address of the next instruction to be fetched.
• Instruction Register (IR): Stores the instruction currently being executed.
• Accumulator (AC): A general-purpose register used for storing the results of arithmetic and logical operations.
• Memory Address Register (MAR): Holds the address of the memory location to be accessed.
• Memory Data Register (MDR): Holds the data being transferred to or from memory.
• Temporary Register (TR): Used for holding temporary data during processing.
• Input/Output Registers (INPR/OUTR): Used for communication with external peripheral devices.

Interrupts are signals sent to the processor by hardware or software indicating that an event needs immediate attention. They allow the CPU to suspend its current task, execute an interrupt service routine (ISR), and then resume the original task.

• Hardware Interrupts: Initiated by external hardware devices (e.g., keyboard, mouse, disk drives) to signal that they require service. These are asynchronous and can be maskable (can be ignored) or non-maskable (must be serviced immediately).
• Software Interrupts: Initiated by the execution of a specific instruction within a program (e.g., system calls). These are synchronous and are used to request operating system services.
• Exceptions (Traps): These are internal interrupts generated by the CPU itself due to errors or abnormal conditions during instruction execution, such as division by zero, invalid opcode, or page faults.