WorksheetsChapter 5: Principles of I/O software
Total questions: 20
Worksheet time: 20mins
List all functions of device independent I/O Software
Uniform interfacing for device drivers.
Buffering and
Error Reporting.
Allocating and releasing dedicated devices.
Providing a device-independent block size.
All answers are Correct
What's asynchronous transfer in principles of I/O software?
The user program starts system call to transfer and automatically suspended until the data are available in the buffer.
The CPU starts the transfer and goes off to do something else until the interrupt arrives.
None of the other choices.
The user process makes system call and goes to sleep until other process it wakes up.
Imagine that a certain modem can read 7,000 characters per second and that the time to read a character to the modem register is so short it can be ignored. If to run this modem using interrupt-driven I/O and each character read requires an interrupt that takes 10 µsec all-in to service. How many percent of the CPU does the interrupt overhead cost?
96% of the CPU
4% of the CPU
93% of the CPU
7% of the CPU
Which of the following statements is not correct about DMA ?
The operating system can only use DMA if the hardware has a DMA controller
DMA controller has access to the system bus independent of the CPU
DMA controller is usually faster than CPU
DMA helps reduce the number of interrupts (in comparison with interrupt-driven I/O)
Which statement about DMA is incorrect?
The CPU can start a DMA block transfer, and in the mean time do other work
The CPU needs not to be concerned with the time it takes to transfer data
The controller does not need to wait for the CPU to transfer data to/from memory
It is always true that DMA is less expensive than CPU-mediate data transfers
Which of the following statements about interrupts and trap instructions is incorrect?
A trap instruction is a software-generated interrupt
An interrupt handler deals with the cause of the interrupt
An interrupt is a hardware-generated change of control flow within the system
None of the other choices
The I/O technique where the processor busy waits for an I/O operation to complete is called:
Programmed I/O
Direct Memory Access (DMA)
Interrupt-driven I/O
None of the other choices
Which of the following statements about the task of device controller of I/O devices is correct ?
Make available to main memory
Convert serial bit stream to block of bytes
Perform error correction as necessary
All of the other choices
DMA operations require the following information from the processor
Address of I/O device
Starting memory location to read from and write to
Number of words to be read or written
All of the other choices
In general the two interrupt request lines are:
Maskable & non maskable interrupts
Blocked & non maskable interrupts
Maskable & blocked interrupts
None of the mentioned
The _________ are reserved for events such as unrecoverable memory errors.
Non maskable interrupts
Blocked interrupts
Maskable interrupts
None of the mentioned
For large data transfers, _________ is used.
DMA
Programmed I/O
Controller register
None of the mentioned
The ________ can be turned off by the CPU before the execution of critical instruction sequences that must not be interrupted.
Nonmaskable interrupt
Blocked interrupt
Maskable interrupt
None of the mentioned
A character stream device transfers:
Bytes one by one
Block of bytes as a unit
With unpredictable response times
None of the mentioned
Buffering is done to:
Cope with device speed mismatch
Cope with device transfer size mismatch
Maintain copy semantics
All of the mentioned
The ________ keeps state information about the use of I/O components.
CPU
OS
Kernel
Shell
Asynchronous transmission is described as the:
Transmission in which the transmitter and receiver of the data transmit and receive data at different rates
Transmission in which the transmitter and receiver of the data transmit and receive data at same rates
Transmission of start and stop bits are completed before the data transmission commences
Clocking frequency of transmission is synchronized with each bus cycle
Synchronous transmission differs from asynchronous transmission in that:
The frequency clocks of the sending and receiving components are synchronized before transmission commences
Transmission is initiated independent of a monitoring clock
The start and stop data bits are unified before transmission commences
The sending capacity and receiving capacity of the connections are unified before transmission
Which buffer holds the output for a device?
Spool
Output
Status
Magic
All the output information that is to be transferred to an output device is placed in
Instruction Register
Input/output Register
Control Register
Buffer Register
