JNTU B.Tech II PRINCIPLES OF PROGRAMMING LANGUAGES Previous Question Paper (September/October - 2023 - R13)

An attribute grammar for simple assignment statements can be defined as follows:

Non-terminals:

assign (assignment statement)

expr (expression)

Terminals:

id (identifier), := (assignment operator), +, -, *, / (arithmetic operators), (, ) (parentheses)

Attribute:

synthesized attribute: val (the value of the expression)

Production Rules:

The attribute grammar would associate semantic rules with these productions to compute the value of the expression.

A Virtual Machine (VM) is a software-based emulation of a computer system. It mimics the hardware of a physical computer, allowing multiple operating systems and applications to run on a single physical machine as if they were on separate, independent computers.

Key aspects of a Virtual Machine:

• Abstraction: VMs provide an abstraction layer over the physical hardware, isolating the guest operating system and applications from the underlying hardware.
• Isolation: Each VM operates in its own isolated environment, preventing issues in one VM from affecting others or the host system.
• Portability: VM images can be easily moved and run on different physical hardware, provided the virtualization software is compatible.
• Resource Management: Virtualization software (hypervisor) manages and allocates physical resources (CPU, memory, storage, network) to the VMs.
• Execution Environment: VMs execute instructions in a controlled environment, often translating them for the host CPU or running them on a simulated CPU.

In programming languages, VMs are crucial for platform independence (e.g., Java Virtual Machine - JVM) and for executing intermediate code like bytecode.