Electronics and Communication Engineering - Microprocessors - Discussion

7. 

To multiply a number by 8 in 8085 we have to use RAL instruction

[A]. once
[B]. twice
[C]. thrice
[D]. four times

Answer: Option C

Explanation:

When RAL instruction is used once the number is doubled.


Navya said: (Jun 11, 2014)  
Sir,

Can you explain what is RAL?

K.Supriya said: (Jun 18, 2014)  
Sir, Please explain this RAL ?

Alpesh said: (Jul 30, 2014)  
Sir, What is the RAL?

Kaushik R said: (Jul 31, 2014)  
RAL means rotate accumulator to left with carry.

Sambhji said: (Aug 2, 2014)  
How answer is thrice, can you explain?

Saurabh said: (Nov 7, 2014)  
There is no multiplication instruction in the 8085.

These operations are equivalent to multiplying by 2:

1) Shift left by 1 (shifting left by n is multiplying by 2^n).

2) Add the value to itself once.

So 2^3 = 8.

Khan. said: (Jul 7, 2016)  
Sir, not understand this. Please explain me in detail.

Quant said: (Jul 7, 2016)  
Sir I can't understand please can you explain in a simple way.

Meena said: (Jul 27, 2016)  
The answer is simple.

Let's take a value 0100 ---> 4.

1st time: Just apply left shift operation on that value 01000 ---> 8(4 * 2^1).
2nd time: again do the same thing 010000 ---> 16(4 * 2^2).
3rd time: again left shift the value 0100000 ---> 32(4 * 2^3).
So by doing three times left shift we are getting eight times of that value.
So the answer is thrice.

Sagar Prajapat said: (Jul 28, 2016)  
Please understand;

1<<1=2 0001<<1= 0010.

1<<2=4 0001<<2= 0100.

1<<3=8 0001<<3= 1000.

Phope said: (Aug 5, 2016)  
#Meena.

8 time, please explain how the last line?

Jaideep said: (Sep 12, 2016)  
@Meena, how the last line become 8 times?

Afzal said: (Sep 17, 2016)  
@Jaideep,

Last line is simple as that of first two. Initially she takes 4 i.e. 0100 and in the last line we got 32 which is nothing but 8 x 4 = 32. Thats only the answer that we wanted.

Abyson said: (May 29, 2017)  
Very helpful, Thanks @Meena.

Priyank said: (Jun 7, 2017)  
How can RAL lead to multiplication as in this instruction the MSB is loaded into carrying flag while moving the whole data to the left by one bit and simultaneously moving the initial carry flag value to the LSB?

Let, Acc-: 01100011b = 99d,
C-: 0
Now, after RAL instruction the value in Acc will be -: 11000110b = 188d not equal to 2 * 99.

So, RAL cannot perform multiplication.

Manjunatha said: (Aug 26, 2017)  
@Priyank.

11000110 (B) is = 198 (D), RAL instruction is used as Multiplication.

Prasann said: (Sep 24, 2018)  
If it is multiplied by 16 means, what is the answer?

Chandan Jeeva said: (Sep 29, 2018)  
4 is the answer.

00001.

Perform left shift by four times then it will be come 10000=16.

In microprocessor to multiply any number we have to move the data to accumilatorand RAL is used how much time we have to multiply that number account to above calculation.

Ramesh Kumar said: (Aug 15, 2019)  
Thanks all for explaining.

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