Explore topic-wise InterviewSolutions in Current Affairs.

The ability to do things well, successfully, without wasting time.

Ability to continue to do something, even when it is difficult.

Determination and perseverance is a combination of attributes and abilities that drive people to set goals for themselves and then to take the initiative to achieve these goals. Douglas was able to overcome his fear of water by the values of positive attitude and courage. Initially he was afraid of water but his grit and determination made him get an instructor to train him and overcome his fear. Determination today leads to our success tomorrow. It is that innate quality in our soul, which comes to surface when we face difficult tasks. It is a reflection of our values taught to us by society and circumstances and enables us to overcome all obstacles.

The key difference between the tuples and lists is that while the tuples are immutable objects the lists are mutable. This means that tuples cannot be changed while the lists can be modified. Tuples are more memory efficient than the lists.

i. Correct Answer: b

ii. Correct Answer: d

iii. Correct Answer: d

iv. Correct Answer: b

v. Correct Answer: c

I a. SELECT NAME, GAME FROM STUDENTS, SPORTS WHERE STUDENTS.ADMNO=SPORTS.ADMNO AND ADDRESS IS NOT NULL;

II a. ALTER TABLE STUDENTS DROP PHONE;

III Correct Answer: c. A AND D

IV a. SELECT NAME, COACHNAME FROM STUDENTS,SPORTS WHERE CLASS LIKE “12%” AND STUDENTS.ADMNO=SPORTS.ADMNO ;

V a. SELECT COUNT(*) FROM STUDENTS,SPORTS WHERE GAME=”VOLLEYBALL” AND STUDENTS.ADMNO=SPORTS.ADMNO

1. Correct Answer : ii. Statement 2

2. Correct Answer: d. Statement 6

3. Correct Answer: d. Statement 6

4. Correct Answer: c. Statement 4

5. Correct Answer: d. Statement 5

I. Correct Answer: b. Star topology

II. Correct Answer: d. Broadband

III. Correct Answer: a. Switch/Hub

IV. Correct Answer: d. Radio waves

V. Correct Answer: b. BLOCK B1

i. Correct Answer: a queue.append(a)

ii. Correct Answer: a isEmpty(Queue)

iii. Correct Answer: b) del queue[0]

iv. Correct Answer : a isEmpty( )

v. Correct Answer : b. print(queue[0:len(queue)])

I. Correct Answer: d. a

II. Correct Answer: b. csv.writer(csvf)

III. Correct Answer: b. cw.writerow(['Title','Author','Price'])

IV. Correct Answer: b. csv.reader(csvf)

V. Correct Answer: a. r[0][0]=='R'

 i. Correct Answer : a. F= open("STUDENT.DAT",'wb')

ii. Correct Answer : c. pickle.dump(L,F)

iii. Correct Answer : a. R = pickle.load(F)

iv. Correct Answer : d

v. Correct Answer : d

1. c. csv

2. b. "Student.csv","w"

3. c. writer(fh)

4. d. roll_no,name,Class,section

5. c. rec

6. c. writerows()

1. Correct Answer : c) csv

2. Correct Answer : b) "Student.csv","w"

3. Correct Answer : c) writer(fh)

4. Correct Answer : d) roll_no,name,Class,section

5. Correct Answer : c) writerows()

Answer is a. read()

Default values can be provided the function prototype itself and the function may be called even if an argument is missing. But there is one limitation with it, if you want to default a middle argument, then all the argument on its right must also be defaulted. For instance, consider the following function prototype:

float amount(float p,

int time=2, float rate=0.08);

cout<<amount(2000,0.13);

Here, C++ will take 0.13 to be the argument value for time and hence invoke amount() with values 2000, 0(0.13 converted to int) and 0.08

Function overloading can handle all possible argument combinations. It overcomes the limitation of default argument but also compiler is saved from the trouble of testing the default value.

Example:

float area(float a)

{

return a*a;

}

float area(float a,float b)

{

retur a*b;

}

Output: 

# # # #

 9 18 27 

The name of feature of Object Oriented Programming used in the above program jointly illustrated by the functions [I] to [IV] is known as ‘function overloading’.

int sum(int a[ ])

{

int n,sum=0;

cout<<"Enter n:";

cin>>n;

for(int i=0;i<n;i⁺⁺)

{

sum=sum+a[i];

}

return sum;

}

//

int sum(int a[ ],char c)

{

int even=0,odd=0;

switch(c)

{

case 'E':

for(int i=0;i<5;i⁺⁺)

{

if(a[i]%2==0)

{

even = even+a[i];

}

}

 return even;

case 'O':

for(int j=0;j<5;j++)

{

if(a[j]%2!=0)

{

odd=odd+a[j];

}

}

return odd;

}

}

1. Few lines of code may be repeatedly used in different contexts. Duplication of the same code can be eliminated by using functions which improves the maintenance and reduce program size.

2. Some functions can be called multiple times with different inputs.

The execution of the program begins at main function.

The default data type returned by a function is int

(d) None of these

The derived data type or user defined data type is created by using basic data types.

For example, structure 

1.  isalpha(): Returns a non-zero value if the argument is a A-Z or a-z letters.

For example, isalpha(‘a’)

output: 1 means true isalpha(‘5’) output: 0 means false

2. toupper( ): It converts the lower case alphabet character to upper case. 

For example, toupper(‘a’)

output: A

Data types are classified into built in or basic data types and user defined or derived data types.

The copy command is Ctrl + C and Ctrl + V is for Paste in Word Processor. 

The sequence of short cut keys to cut and paste is Ctrl+X for cut and Ctrl+V for paste.

1.  isalpha() returns a non-zero value if argument is A-Z or a-z letters.

For example, isalpha(‘a’) output: true isalpha(‘5’)

output: false

2.  toupper () function converts the lower case alphabet character to upper case.

For example, toupper(‘a’)

output: A 

1. Local scope: A variable declared inside a block can be used only in the block. It cannot be used any other block. 

eg: #include<iostream>

using namespace std; 

int sum(int n1 ,int n2) 

{

int s; s = n1 + n2; 

return (s); 

} 

int main() 

{ 

int n1 ,n2; 

cout<<“Enter 2 numbers cin>>n1>>n2;

cout<<“The sum is “<<sum(n1 ,n2);

} 

Here the variable s is declared inside the function sum and has local scope;

2. Global scope: 

A variable declared outside of all blocks can be used any where in the program. 

#include<iostream>

using namespace std; 

int s; 

int sum(int n1,int n2) 

{ 

s = n1 + n2; 

return(s); 

} 

int main() 

{ 

int n1 ,n2;

cout<<“Enter 2 numbers cin>>n1>>n2;

cout<<“The sum is “<<sum(n1 ,n2);

} 

Here the variable s is declared out side of all functions and we can use variable s any where in the program.

(d) name of the parameters

void key word is used to specify a function returns nothing.

parameters (arguments)

After the execution of a function, it is returned back to the main function by executing return keyword.

The output is 123 + 45 = 168. Here the conversion function atoi is used to convert the string “123” into integer 123 and “45” into integer 45 so the result.

Methods of calling functions: 

Two types call by value and call by reference. 

1. Call by value: 

In call by value method the copy of the original value is passed to the function, if the function makes any change will not affect the original value. 

Example

#include<iostream.h>

#include<conio.h>

void swap(int a, int b)

{

int temp;

temp = a;

a =b;

b = temp;

}

main()

{

cirscr();

int a,b;

cout<<"Enter value for a and b:-";

cin>>a>>b;

{

cout<<"The value before swap a="<<a<<"and b="<<b;

swap(a,b);

cout<<"\n The value before swap a="<<a<<"and b="<<b;

getch();

}

2. Call by reference: 

In call by reference method the address of the original value is passed to the function, if the function makes any change will affect the original value. 

Example

#include<iostream.h>

#include<conio.h>

void swap(int& a, int& b)

{

int temp;

temp = a;

a =b;

b = temp;

}

main()

{

cirscr();

int a,b;

cout<<"Enter value for a and b:-";

cin>>a>>b;

cout<<"The value before swap a="<<a<<"and b="<<b;

swap(a,b);

cout<<"\n The value before swap a="<<a<<"and b="<<b;

getch();

}

There are five modes of operations in 8253

MODE 1: HARDWARE RETRIGGERABLE ONE-SHOT 

OUT will be initially high. OUT will go low on the CLK pulse following a trigger to begin the one shot pulse,and will remain low until the Counter reaches zero. OUT will then go high and remain high until the CLK pulse after the next trigger.After writing the Control Word and initial count, the Counter is armed. A trigger results in loading the Counter and setting OUT low on the next CLK pulse,thus starting the one-shot pulse. An initial count of N will result in a one-shot pulse N CLK cycles in duration. The one-shot is retriggerable, hence OUT will remain low for N CLK pulses after any trigger. The one-shot pulse can be repeated without rewriting the same count into the counter. GATE has no effect on OUT.If a new count is written to the Counter during a one shot pulse, the current one-shot is not affected unless the counter is retriggered. In that case, the Counter is loaded with the new count and the one shot pulse continues until the new count expires.

MODE 2: RATE GENERATOR 

This Mode functions like a divide-by-N counter. It is typically used to generate a Real Time Clock interrupt.OUT will initially be high. When the initial count has decremented to 1, OUT goes low for one CLK pulse. OUT then goes high again, the Counter reloads the initial count and the process is repeated.Mode 2 is periodic; the same sequence is repeated indefinitely. For an initial count of N, the sequence repeats every N CLK cycles. GATE e1 enables counting; GATE e 0 disables counting. If GATE goes low during an output pulse,OUT is set high immediately. A trigger reloads the Counter with the initial count on the next CLK pulse; OUT goes low N CLK pulses after the trigger. Thus the GATE input can be used to synchronize the Counter.After writing a Control Word and initial count, the Counter will be loaded on the next CLK pulse. OUT goes low N CLK Pulses after the initial count is written.This allows the Counter to be synchronized by software also.Writing a new count while counting does not affect the current counting sequence. If a trigger is received after writing a new count but before the end of the current period, the Counter will be loaded with the new count on the next CLK pulse and counting will continue from the new count. Otherwise, the new count will be loaded at the end of the current counting cycle. In mode 2, a COUNT of 1 is illegal. 

MODE 3: SQUARE WAVE MODE

Mode 3 is typically used for Baud rate generation.Mode 3 is similar to Mode 2 except for the duty cycle of OUT. OUT will initially be high. When half the initial count has expired, OUT goes low for the remainder of the count. Mode 3 is periodic; the sequence above is repeated indefinitely. An initial count of N results in a square wave with a period of N CLK cycles. GATEe1 enables counting; GATE e 0 disables counting. If GATE goes low while OUT is low, OUT is set high immediately; no CLK pulse is required. A trigger reloads the Counter with the initial count on the next CLK pulse. Thus the GATE input can be used to synchronize the Counter. After writing a Control Word and initial count, the Counter will be loaded on the next CLK pulse. This allows the Counter to be synchronized by software also.Writing a new count while counting does not affect the current counting sequence. If a trigger is received after writing a new count but before the end of the current half-cycle of the square wave, the Counter will be loaded with the new count on the next CLK pulse and counting will continue from the new count. Otherwise, the new count will be loadedat the end of the current half-cycle.Mode 3 is implemented as follows:Even counts: OUT is initially high. The initial count is loaded on one CLK pulse and then is decremented by two on succeeding CLK pulses. When the count expires OUT changes value and the Counter is reloaded with the initial count. The above process is repeated indefinitely. Odd counts: OUT is initially high. The initial count minus one (an even number) is loaded on one CLK pulse and then is decremented by two on succeeding CLK pulses. One CLK pulse after the count expires,OUT goes low and the Counter is reloaded with the initial count minus one. Succeeding CLK pulses decrement the count by two. When the count expires, OUT goes high again and the Counter is reloaded with the initial count minus one. The above process is repeated indefinitely. So for odd counts,OUT will be high for (N a 1)/2 counts and low for(N b 1)/2 counts.

MODE 4: SOFTWARE TRIGGERED STROBE 

OUT will be initially high. When the initial count expires,OUT will go low for one CLK pulse and then go high again. The counting sequence is ``triggered''by writing the initial count. GATE e1 enables counting; GATE e 0 disables counting. GATE has no effect on OUT.After writing a Control Word and initial count, the Counter will be loaded on the next CLK pulse. This CLK pulse does not decrement the count, so for an initial count of N, OUT does not strobe low until N a1 CLK pulses after the initial count is written.If a new count is written during counting, it will be loaded on the next CLK pulse and counting will continue from the new count. 

If a two-byte count is written,the following happens: 

1) Writing the first byte has no effect on counting. 

2) Writing the second byte allows the new count to be loaded on the next CLK pulse.This allows the sequence to be ``retriggered'' by software. OUT strobes low N a 1 CLK pulses after the new count of N is written.231164±11 MODE 

5: HARDWARE TRIGGERED STROBE (RETRIGGERABLE)

OUT will initially be high. Counting is triggered by arising edge of GATE. When the initial count has expired,OUT will go low for one CLK pulse and the n go high again.After writing the Control Word and initial count, the counter will not be loaded until the CLK pulse after at rigger. This CLK pulse does not decrement the count, so for an initial count of N, OUT does not strobe low until N a 1 CLK pulses after a trigger. A trigger results in the Counter being loaded with the initial count on the next CLK pulse. The counting sequence is retriggerable. OUT will not strobe low for N a 1 CLK pulses after any trigger. GATE has no effect on OUT.If a new count is written during counting, the current counting sequence will not be affected. If a trigger occurs after the new count is written but before the current count expires, the Counter will be loaded with the new count on the next CLK pulse and counting will continue from there.

A default value can be set for a parameter (argument) of a function. When the user does not give a value the function will take the default value. An important thing remember, is an argument cannot have a default value unless all arguments on its right side must have default value. 

Functions with valid default arguments are given below

• float area(int x, int y, int z = 30); 
• float area(int x, int y = 20, int z = 30); 
• float area(int x = 10, int y = 20, int z = 30);

Functions with invalid default arguments are given below 

• float area(int x = 10, int y, int z); 
• float area(int x, int y = 20, int z); 
• float area(int x = 10, int y = 20, int z);

The statement is False.

MODE OF OPERATION OF 8237 

SINGLE TRANSFER MODE

In Single Transfer mode the device is programmed to make one transfer only.The word count will be decremented and the address decremented or incremented following each transfer. When the word count ``rolls over'' from zero to FFFFH, a Terminal Count (TC) will cause an Auto initialize if the channel has been programmed to do so. DREQ must be held active until DACK becomes active in order to be recognized. If DREQ is held active through out the single transfer, HRQ will go in active and release the bus to the system. It will again go active and, upon receipt of a new HLDA, an other single transfer will be performed.

In 8080A, 8085AH, 8088, or 8086 system, this will ensure one full machine cycle execution between DMA transfers. Details of timing between the 8237A and other bus control protocols will depend upon the characteristics of the microprocessor involved. 

BLOCK TRANSFER MODE 

In Block Transfer mode the device is activated by DREQ to continue making transfers during the service until a TC, caused byword count going to FFFFH, or an external End of Process (EOP) is encountered. DREQ need only be held active until DACK becomes active. 

Again, an Auto initialization will occur at the end of the service if the channel has been programmed for it.

DEMAND TRANSFER MODE

In Demand Transfer mode the device is programmed to continue making transfers until a TC or external EOP is encountered or until DREQ goes inactive. Thus transfers may continue until the I/O device has exhausted its data capacity. After the I/O device has had a chance to catch up, the DMA service is re-established by means of a DREQ. During the time between services when the microprocessor is allowed to operate, the intermediate values of address and word count are stored in the 8237 A Current Address and Current Word Count registers. Only an EOP can cause an Auto initialize at the end of the service. EOP is generated either by TC or by an external signal. DREQ has to be low before S4 to prevent another Transfer. 

CASCADE MODE 

This mode is used to cascade more than one 8237A together for simple system expansion. The HRQ and HLDA signals from the additional 8237A are connected to the DREQ and DACK signals of a channel of the initial 8237A. This allows the DMA requests of the additional device to propagate through the priority network circuitry of the preceding device. The priority chain is preserved and the new device must wait for its turn to acknowledge requests. Since the cascade channel of the initial 8237A is used only for prioritizing the additional device, it does not output any address or control.

8254 SYSTEM INTERFACE

The 8254 is a component of the Intel Microcomputer Systems and interfaces in the same manner as all other peripherals of the family. It is treated by the system's software as an array of peripheral I/O ports; three are counters and the fourth is a control register for MODE programming.Basically, the select inputs A0,A1 connect to the A0, A1 address bus signals of the CPU. The CS can be derived directly from the address bus using a linear select method. Or it can be connected to the output of a decoder, such as an Intel 8205 for larger systems

Actual parameter

Input Handshaking signals 

1. IBF(Input Buffer Full)-It is an output indicating that the input latch contains information. 

2. STB(Strobed Input)-The strobe input loads data into the port latch, which holds the information until it is input to the microprocessor via the IN instruction. 

3. INTR(Interrupt request)-It is an output that requests an interrupt. The INTR pin becomes a logic 1 when the STB input returns to a logic 1, and is cleared when the data are input from the port by the microprocessor. 

4. INTE(Interrupt enable)-It is neither an input nor an output; it is an internal bit programmed via the port PC4(port A) or PC2(port B) bit position.

default parameter is used when the function call does not supply a value for parameters

The 8254 is a programmable interval timer/counterdesigned for use with Intel microcomputer systems.

It is a general purpose, multi-timing element that canbe treated as an array of I/O ports in the system software.The 8254 solves one of the most common problems in any microcomputer system, the generation of accuratetime delays under software control. Instead ofsetting up timing loops in software, the programmerconfigures the 8254 to match his requirements and programs one of the counters for the desired delay.After the desired delay, the 8254 will interrupt theCPU. Software overhead is minimal and variablelength delays can easily be accommodated.Some of the other counter/timer functions commonto microcomputers which can be implemented withthe 8254 are: 

# Real time clock 

# Event-counter 

# Digital one-shot 

# Programmable rate generator 

# Square wave generator # Binary rate multiplier 

# Complex waveform generator 

# Complex motor controller

DISPLAY MODE 

(A) LEFT ENTRY MODE 

When the data is entered from the left side of the display unit it is called left entry mode. A dress 15 of the RAM contains the right most display character and address 0 of the display RAM contains the left most display character. 

(B) RIGHT ENTRY MODE 

In this mode the first entry to be displayed is entered on the rightmost display. The next entry is also placed in the right most display but after the previous display i shift left by one display position.

KEYBOARD MODES 

(A.) SCANNED KEYBOARD MODE WITH 2 KEY LOCKOUT

when a key is pressed ,it enters into FIFO (if at least 1 byte is free ),an interrupt is generated to inform CPU about previous key closure, if found no entry is made to the FIFO.If 2 keys are pressed no keys are detected or scanned. 

(B.) SCANNED KEYBOARD SPECIAL ERROR MODE 

Validity of this mode depends on N key rollover mode. when 2 keys are pressed simultaneously, error flag is set, it prevents further writing but sends interrupt to CPU for read operation. With command CF=1,error flag can be set. 

(C.) SENSOR MATRIX MODE 

debounce logic is inhibited.8 byte FIFO RAM acts as 8 x 8 bit memory matrix .

sensor RAM contains status of sensor matrix.

DATABUS BUFFER 

The 8 bit bidirectional data bus connected to data bus of the micro processor. The direction of the data bus are decided by the read and write control signals . in read operation it transmit data to the system bus and in write operation it receives data from system bus.

OUTPUT (DISPLAY) MODE 

2 output modes for selecting display 

1. Display Scan: provides 8 or 16 characters multiplexed displays organised as dual 4 bit or single 8 bit display units 

2. Display Entry: it allows options for data entry into the display either left entry or right entry.