Input-Output systems

Introduction

Input/output (I/O), in the operating system, is a communication process between the outside world and the system. At its primary level, an information system, for example, a software application installed on a system, and its users in the outside world control the system to solve problems. Input refers to the instructions or signals transferred to the system, and Output refers to the signals sent out from the system. 

Refer to this link to learn more about the Input-Output systems.

Problems 

1.  A CPU generally handles an interrupt by executing an interrupt service routine.

1. By checking the interrupt register at the end of the fetch cycle.
2. By checking the interrupt register at fixed time intervals.
3. By checking the interrupt register after finishing the execution of the current instruction.
4. As soon as an interrupt is raised

Ans: c
Explanation: Hardware detects interrupt immediately, but the CPU acts only after its current instruction. This is followed to ensure the integrity of instructions.

2. Which one of these will be handled at the HIGHEST priority?

1. Interrupt from Keyboard
2. Interrupt from the CPU temperature sensor
3. Interrupt from Hard Disk
4. Interrupt from Mouse    

Ans: b
Explanation: Higher priority interrupt levels are allocated to requests that could have severe consequences if delayed or interrupted. Devices with high-speed transfer, such as magnetic disks, are given high priority.

3. Determine the right one to justify the interrupt mode of data transfer among the given following scenarios:

1. Keyboard inputs
2. Moderately large data transfer but more than 1 KB
3. Bulk transfer of several kilo-byte
4. Short events like mouse action

Ans: a,d
Explanation: Both keyboard and mouse controllers typically use interrupt mode.

4. Which of the following is a significant part of the time taken when accessing data on the disk?

1. Rotational latency
2. Seek time
3. Settle time
4. Waiting time

Ans: b
Explanation: Among all of the above, seek time is the time taken by the head to process to the path of the disk where the data to be accessed is stored, and it is a significant part of the time taken when accessing data on the disk.

5. The data blocks of a large file in the Unix file system are allocated using

1. linked allocation
2. indexed allocation
3. an extension of indexed allocation
4. contiguous allocation

Ans: c
Explanation: The Unix file system utilizes an extension of indexed allocation. It has direct blocks, single indirect blocks, double indirect blocks, and triple indirect blocks. 

6. By using a larger block size in a fixed block size file system causes :

1. poorer disk throughput but better disk space utilization
2. poorer disk space utilization and poorer disk throughput
3. better disk throughput but poorer disk space utilization
4. better disk space utilization and better disk throughput 

Ans: c
Explanation: Since more space would be wasted for small data in a block hence using a larger block size makes disk utilization poorer. It can make throughput better since the number of blocks would decrease. A larger block size makes sure that more data from a single file will be read or written at a time into a single block without moving the disk ́s head.

7. Which of the following will require a device driver?

1. Main memory
2. Cache
3. Disk
4. Register

Ans: c
Explanation: A disk drive is a software that enables the communication between the internal hard disk (or drive) and the computer. It allows a specific disk drive to interact with the remainder of the computer.

8. Among these, which of the following DMA transfer modes and interrupt handling mechanisms would invoke the highest I/O bandwidth? 

1. Transparent DMA and Polling interrupts
2. Block transfer and Polling interrupts
3. Cycle-stealing and Vectored interrupts
4. Block transfer and Vectored interrupts

Ans: d
Explanation: Among all types of DMA transfer modes and interrupt handling mechanism Block transfer and vector interrupts would invoke the highest I/O bandwidth.

9. Among the following, which of them is an example of a spooled device?

1. a graphic display device
2. a secondary storage device in a virtual memory system
3. a terminal that enters input data to a running program
4. a line printer that prints the output of a number of jobs

Ans: d
Explanation: Among all of the above a line printer that prints the output of a number of jobs is an example of a spooled device.

10. Special software used to create a job queue is called a

1. Driver
2. Spooler
3. Interpreter
4. Linkage editor

Ans: b
Explanation: A spooler is software that works on creating a request queue where instructions, data, and processes from many sources are stored for execution later on.   

We will close the article now with faqs since you get some idea of the gate questions related to Input-Output systems.