INSIGHT INTO PROGRAM EXECUTION || Class 11 || Computer Science

 

INSIGHT INTO PROGRAM EXECUTION

Short Answer Type Questions 

Q.1     What are the front end and back end phases of compiler?

Ans: The front end phase of compiler is Analysis Phase. This phase of compilation identifies all the tokens in the source code and creates a symbol table with it.

 The back end phase of compiler is Synthesis Phase. This phase of compiler parses the code and generates syntax tree, analyzing the syntax of the source code.  Q.2 Differentiate between compiler and interpreter.

Ans:  

Aspects	Compiler	Interpreter
Input	A Compiler takes an entire program as its input.	It takes a single line of code or single instruction(such as loop) as its input.
Output	It generates intermediate object code from the whole program.	It does not create any intermediate object code.
Memory	Requires        more   memory           during compilation.	Requires less memory during interpretation as interprets single instruction/unit-of-code at a time.
Errors	Displays lists of errors of entire program with line numbers and the error(s) in that line.	Displays the error of single line it is interpreting. Thus errors also appear one line at a time.
Always Required	No. once the role of compiler is over, a compiler is no longer required to run the executable fuile.	Always required. Interpreter translates and runs one instruction every time. So it is always required in memory to run the code.
Workload	Compilation once done, stays always. Recompilation not required if the code(without any change) needs to run again. The same executable file can be rerun without the compiler.	Interpretation is required each time you have to run the code. The interpreter does not create an executable and hence it is required every time, the code is to run.

 

 

 

Q.3              What are the characteristics of compiler? 

Ans:

Aspects	Compiler
Input	A Compiler takes an entire program as its input.
Output	It generates intermediate object code from the whole program.
Memory	Requires more memory during compilation.
Errors	Displays lists of errors of entire program with line numbers and the error(s) in that line.
Always Required	No. once the role of compiler is over, a compiler is no longer required to run the executable fuile.
Workload	Compilation once done, stays always. Recompilation not required if the code(without any change) needs to run again. The same executable file can be rerun without the compiler.

Q.4               What are the characteristics of Interpreter?

Ans:

Aspects	Interpreter
Input	It takes a single line of code or single instruction(such as loop) as its input.
Output	It does not create any intermediate object code.
Memory	Requires less memory during interpretation as interprets single instruction/unit-of-code at a time.
Errors	Displays the error of single line it is interpreting. Thus errors also appear one line at a time.
Always Required	Always required. Interpreter translates and runs one instruction every time. So it is always required in memory to run the code.
Workload	Interpretation is required each time you have to run the code. The interpreter does not create an executable and hence it is required every time, the code is to run.

 

 

Q.5   Describe the role of Operating System as a resource Manager.

Ans: A computer system has many resources (hardware and software), which may be require to complete a task. The commonly required resources are input/output devices, memory, file storage space, CPU etc. The operating system acts as a manager of the above resources and allocates them to specific programs and users, whenever necessary to perform a particular task. Therefore operating system is the resource manager i.e. it can manage the resource of a computer system internally. The resources are processor, memory, files, and I/O devices. In simple terms, an operating system is the interface between the user and the machine.

   Operating System Management Tasks

1.   Processor management which involves putting the tasks into order and pairing them into manageable size before they go to the CPU.

2.   Memory management which coordinates data to and from RAM (random-access memory) and determines the necessity for virtual memory.

3.   Device management which provides interface between connected devices.

4.   Storage management which directs permanent data storage.

5.   Application which allows standard communication between software and your computer.

6.   User interface which allows you to communicate with your computer. Q.6          What is cloud computing?

Ans: cloud computing is the delivery of computing services—servers, storage, databases, networking, software, analytics, intelligence and more—over the Internet (―the cloud‖) to offer faster innovation, flexible resources and economies of scale. You typically pay only for cloud services you use, helping lower your operating costs, run your infrastructure more efficiently and scale as your business needs change.

Cloud computing is a big shift from the traditional way businesses think about IT resources.

Here are seven common reasons organizations are turning to cloud computing services. Q.7      What are the advantages of parallel computing?

Ans: Parallel computing is a type of computation in which many calculations or the execution of processes are carried out simultaneously. Large problems can often be divided into smaller ones, which can then be solved at the same time. It refers to the simultaneous working of multiple processors to solve a computational problem. Its advantages are –  (i) It saves time and the cost too.

(ii)         It makes easier to solve larger or complex problems.

(iii)        It provides efficient use of underlying hardware.

(iv)       It can utilize the resources available remotely. Q.8  What is the basic flow of program execution?

Ans: the basic flow of program execution can be defined when a programmer create a program( the source code), which needs to be converted into binary form so that computer can execute it.

This conversion is done by a software which is known as translator(compiler or interpreter).

 

Q.9 What is the difference between source code and object code?

Ans: Source Code refers to the original code written in a programming language by a programmer. Object Code refers to the code converted into computer understandable form that a computer can understand and can directly execute. Q.10 What are the steps of compilation?

Ans: The compilation mainly undergoes these steps:

(i)          Preprocessing

(ii)         Compilation

a.    Analysis

b.    Synthesis

(iii)        Assembly

(iv)       Linking

Q.11 What is the role of linker in a compiler?

Ans: The part of the compiler which performs the linking of libraries is called linker. In this phase, with the help of OS, all memory references are resolved and code is converted to a form which requires nothing else to run.that is, the code has become executable (.exe. file) now. Q.12 How is interpretation done?

Ans: Unlike compiler, an interpreter doesn‘t translate the complete code in one go and hand over a full executable file to execute. Instead, an interpreter translates a single line/section of code at a time, makes its executable version and suns it immediately. Q.13 How is a process different from a program?

Ans: A running program or the executing entity is called a process. So a program is a passive entity when it is stored in storage. When it is copied to memory to get executed and starts its execution then the program is known as process.

 

Q.14    What is process scheduling?

Ans: The process scheduling is the activity of the process manager that handles the removal of the running process from the CPU and the selection of another process on the basis of a particular strategy.

Process scheduling is an essential part of a Multiprogramming operating systems. Such operating systems allow more than one process to be loaded into the executable memory at a time and the loaded process shares the CPU using time multiplexing.

 

Q.15    What are process scheduling queues?

Ans: The OS maintains all PCBs in Process Scheduling Queues. The OS maintains a separate queue for each of the process states and PCBs of all processes in the same execution state are placed in the same queue. When the state of a process is changed, its PCB is unlinked from its current queue and moved to its new state queue.

The Operating System maintains the following important process scheduling queues −  Job queue − This queue keeps all the processes in the system.

•        Ready queue − This queue keeps a set of all processes residing in main memory, ready and waiting to execute. A new process is always put in this queue.

•        Device queues − The processes which are blocked due to unavailability of an I/O device constitute this queue.

Q.16 How does OS manage all the running processes?

Ans: Process managements involve the execution of various tasks such as creation of processes, scheduling of processes, management of deadlock, and termination of processes. It is responsibility of operating system to manage all the running processes of the system. Operating system manages processes by performing tasks such as resource allocation and process scheduling. When a process runs on computer device memory and CPU of computer are utilized. The operating system also has to synchronize the different processes of computer system.

A process consists of set of instruction to be executed called process code. A process is also associated with some data that is to be processed. The resources that a process required for its execution is called process components. There is also a state that is associated with a process at a particular instant of time called process state. Similar to these concepts, there are number of concepts associated with the process management function of an operating system. Some of those concepts are given as following.

•        Process State

•        Process Control Block (PCB)

•        Process Operations              Process Scheduling

•        Process Synchronization

•        Interprocess Communication

•        Deadlock

Q.17 What is the role of memory manager and I/O manager of OS?

Ans: Memory management is a form of resource management applied to computer memory. The essential requirement of memory management is to provide ways to dynamically allocate portions of memory to programs at their request, and free it for reuse when no longer needed. This is critical to any advanced computer system where more than a single process might be underway at any time.

I/O Manager:One of the important jobs of an Operating System is to manage various I/O devices including mouse, keyboards, touch pad, disk drives, display adapters, USB devices, Bitmapped screen, LED, Analog-to-digital converter, On/off switch, network connections, audio I/O, printers etc.

An I/O system is required to take an application I/O request and send it to the physical device, then take whatever response comes back from the device and send it to the application. I/O devices can be divided into two categories −

•        Block devices − A block device is one with which the driver communicates by sending entire blocks of data. For example, Hard disks, USB cameras, Disk-On-Key etc.

•        Character devices − A character device is one with which the driver communicates by sending and receiving single characters (bytes, octets). For example, serial ports, parallel ports, sounds cards etc

Q.18    How is private cloud different from public cloud?

Ans: Public cloud: Public clouds are owned and operated by a third-party cloud service providers, which deliver their computing resources like servers and storage over the Internet. Microsoft Azure is an example of a public cloud. With a public cloud, all hardware, software and other supporting infrastructure is owned and managed by the cloud provider. You access these services and manage your account using a web browser.

Private cloud: A private cloud refers to cloud computing resources used exclusively by a single business or organization. A private cloud can be physically located on the company‘s on-site datacenter. Some companies also pay third-party service providers to host their private cloud. A private cloud is one in which the services and infrastructure are maintained on a private network.

Q.19    What is parallel computing?

Ans: Parallel computing is a type of computation in which many calculations or the execution of processes are carried out simultaneously. Large problems can often be divided into smaller ones, which can then be solved at the same time. It refers to the simultaneous working of multiple processors to solve a computational problem.

Q.20    How is parallel computing different from serial computing?

Ans:  Serial Computing: A processing in which one task is completed at a time and all the tasks are run by the processor in a sequence. In real time example, people standing in a queue and waiting for a railway ticket. In this case, one person can get a ticket at a time. Suppose there are two queues of people and one cashier is handling both the queues then one person can get a ticket at a time from both queues. Similarly, processor get lists of tasks and each task is completed at a time and all other tasks wait till the first one completes. This type of processing is also known as sequential processing.

 Parallel Computing: A type of processing in which multiple tasks are completed at a time by different processors. Note that in parallel processing there is more than one processor involved. In real time example, there are multiple queues of people standing to get railway tickets. In this case, each queue is handled by multiple people, so multiple people will get tickets at a time. Similarly, in the operating system, there are multiple queues of tasks and multiple tasks are completed by different processors at a time.

Q.21    What are the advantages of parallel computing?

Ans: Parallel computing is a type of computation in which many calculations or the execution of processes are carried out simultaneously. Large problems can often be divided into smaller ones, which can then be solved at the same time. It refers to the simultaneous working of multiple processors to solve a computational problem. Its advantages are –  (i) It saves time and the cost too.

(ii)         It makes easier to solve larger or complex problems.

(iii)        It provides efficient use of underlying hardware.

(iv)       It can utilize the resources available remotely. Q.22 What is PCB? What is its role?

Ans: While creating a process the operating system performs several operations. To identify these process, it must identify each process, hence it assigns a process identification number (PID) to each process. As the operating system supports multi-programming, it needs to keep track of all the processes. For this task, the process control block (PCB) is used to track the process‘s execution status. Each block of memory contains information about the process state, program counter, stack pointer, status of opened files, scheduling algorithms, etc. All these information is required and must be saved when the process is switched from one state to another. When the process made transitions from one state to another, the operating system must update information in the process‘s PCB.

               A process control block (PCB) contains information about the process, i.e. registers, quantum,

priority, etc.

 

 

 

 

 

 

 

 

             Pointer – It is a stack pointer which is required to be saved when the process is switched from

one state to another to retain the current position of the process.

Process state – It stores the respective state of the process.

Process number – Every process is assigned with a unique id known as process ID or PID which stores the process identifier.

Program counter – It stores the counter which contains the address of the next instruction that is to be executed for the process.

Register – These are the CPU registers which includes: accumulator, base, registers and general purpose registers.

Memory limits – This field contains the information about memory management system used by operating system. This may include the page tables, segment tables etc.

Open files list – This information includes the list of files opened for a process.