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CS609_Midterm_System Programming spring 2015 (Held On Dated 20-JUNE-2015)

Total Questions: 26 Total Marks: 40

Objective: 20 marks, Subjective 20 marks

Q.21 When we discuss flow control using RS232C. Which line is used for data transmission and reception? (2 marks)

Answer: (Page 110, 111)

RS232C is a standard for physical dimension of the connector interconnecting a DTE (Data terminal equipment) and DCE (Data communication equipment). Data is received through the RxD line. Data is send through the TxD line.

Q.22 What will be the binary value of LED status byte if the scroll lock and num lock LED on? (2 marks.)

Answer: (Page 181)

0xF3 used for type matic rate

oxED used for LEDS

Q.23 In flow control what is the working of D4? (3marks)

Answer: (page 101)

First the low nibble of the byte is sent from the sender in bit D0 to D3 of the data port. D4 bit is cleared to indicate the low nibble is being sent. The receiver will know the arrival of the low nibble when its checks BUSY bit which should be set (by the interface) on arrival.

Q.24 What are the usages of coprocessor control word in coprocessor while testing for coprocessor? (3 marks)

Answer: (page 168)

The coprocessor control word contains some control information about the coprocessor. The bit number 7 of coprocessor control word is the Interrupt Enable Flag and bit number 8 & 9 should contain 11 on initialization.

Q.25 Write an initialize function to initialize COM ports using BIOS services? (5 marks)

Answer: (page 127)

#include <dos.h>

#include <bios.h>

void initialize (unsigned int far *com)


outportb ( (*com)+3, inport ((*com)+3) | 0x80);

outportb ( (*com),0x80);

outportb( (*com) +1, 0x01);

outportb ( (*com)+3, 0x1b);


Q.26 Draw/Write structure of status registers C? (5 marks)

Answer: (page 146)

Views: 2148


Replies to This Discussion

thankx bro

Are all these are correct answers????

The memory addresses of COM ports remain same for all computers ►True

 ►False  correct


If we use keep (0, 1000) in a TSR program, the memory allocated to it is ► 64000 bytes

► 32000 bytes

 ► 16000 bytes correct

 ► 80000 bytes


We have set the bit No. 7 of IMR(Interrupt Mask Register) to unmask the Interrupt so that interrupt _____ can occur at ____ line.

 ►0xf ,IRQ 7  correct

► 0xa, IRQ 6

► 0x8, IRQ 5

 ►0x6, IRQ 2


If we want to produce the grave voice from speaker phone then we have to load the ____ divisor values at Port ____.

 ►high, 0x42

►low, 0x22

►high, 0x22

►low, 0x42  correct


 In order to produce the sound from PC internal Speaker we have to load the___bit divisor value at the ___port. ►8, 0x21   correct

►16, 0x42

►32, 0x22

►64, 0x32


In keyboard status byte bit no. 2 and 3 are used for ctrl and alt keys respectively. which of the following condition is used to check that Ctrl + Alt keys are pressed. Where: unsigned char far * scr = (unsigned char far *)(0x00400017);

►if (((*scr)&12)==12) correct

►if (((*scr)&8)==8)

►if (((*scr)&4)==4)

►if (((*scr)&2)==2)


pla share cs609 paper


plz share the current ppr

plzzzzzzzzzz :(  

plz share today paper cs 609 any one..... plz

21. In 64H what the purpose of
IBF and OBF.(2)
A:  A certain bit in the port 64H is used as the IBF bit. IBF bit is used to recieve character from keyboard. 

OBF used to send data to keyboard. 

22.FIFO Queue. Why we need this buffer.?(2)
A: This is a feature in newer version of UART which is 16500. A queue or a buffer of input and output bytes is maintained within the UART in order to facilitate more efficient I/O. The size of the queue can be controlled through this register.

23.What the usage of coprocessor control word while testing for coprocessor? (3)

A: Co-processor control word is contains some control information about coprocessor.

The bit number 7 of coprocessor control word is interrupt enable flag and the bit number 8 n 9 should contain 11 on initialization. 

24.Suppose we have got the status byte of LPT1 port using BIOS function int 17H.Write the condition in C language that can check the time out, transfer error and out of paper error.(3)

A: 17AH/00H

On entery


AL= ASCII code

DX=interface number

On exit

DX=status byte

25. Draw the status of Clock Status C register.(5)

A: It can be used for describing reasons of interrupts. 

26. Define UART. Explain the purpose/usage of UART. (5)

A: UART is a devise which is used for asynchronous communication. UART is capable for encapsulating a byte that might be 5,6,7 or 8 bits in start and stop bits. It can attach an extra parity bit with the data for error deduction. The width of stop bits may also vary. 

Q. Step to access battery powered ram. (5 Marks) Answer:- (Page 144) Battery Powered RAM is accessed in two steps • Specify the Byte no. in 70H port. • Read/write port 71H to get/set the value of specified byte. Following slide shown a fragment of code that can be used to read or write onto any byte within the 64 byte battery powered RAM. outport (0x70, 0); outport (0x70, 4); sec = inport (0x71); outport (0x71,hrs);

This is done by sending the code 0XED before sending the status
byte using the above described protocol.

what is the meaning of this code at receiver end in parallel communication unsigned int far * lpt = (unsigned int far *)0x00400008; if ((( inport((*lpt) +1)) & 0x80) == 0x80)

4) what type of information send to keyboard Answer:- (Page 179) Some data (as control information) can be send to the keyboard. The processor will write on the port 60H. The device driver will check the OBF( output buffer full bit of port 64H which remains set as long as the byte is not received by the keyboard.


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