Assembly Language Discussion Thread
Anish
Spectre
Re: Assembly language programing in 8086up......!!
repeated subtraction is the logic..
1. Get the divisor and divident
2. subtract the divisor as many times as you can without a carry
3. The number of times you can subtract without getting a carry is the quotient
For example, to divide 4 by two,
I am just writing the algorithm..
repeated subtraction is the logic..
1. Get the divisor and divident
2. subtract the divisor as many times as you can without a carry
3. The number of times you can subtract without getting a carry is the quotient
For example, to divide 4 by two,
I am just writing the algorithm..
Code:
move 4,r1 //4 is loaded in register 1
move 2,r2 //2 is loaded in register 2
clear r3 //register 3 is cleared to hold the quotient
start: sub r1,r2 //r2 contents (2) is subtrated from r1 contents(4) and answer is placed in r1
inc r3 //r3 is incremented .i.e. we have succesfully subtracted 2 from 4 once
jnc start // if carry flag isnt set, go to the label start and continue the loop
end //if carry flag is set, end the program
MetalheadGautham
AFK
Re: Assembly language programing in 8086up......!!
Finished this course last semester and learnt 8086 and PIC16 assembly languages... Sheesh, wish I'd seen this thread sooner....
Finished this course last semester and learnt 8086 and PIC16 assembly languages... Sheesh, wish I'd seen this thread sooner....
Anish
Spectre
Re: Assembly language programing in 8086up......!!
Hi ritesh, here is the program for dividing two numbers. In my example, i took 23h and divided it by 05h and the quotient is 07h. I've made quotient to appear in the register A.
Here, you can replace 23h and 05h by any 8 bit number.
Hi ritesh, here is the program for dividing two numbers. In my example, i took 23h and divided it by 05h and the quotient is 07h. I've made quotient to appear in the register A.
Code:
mvi a,23h
mvi c,05h
inr b
sub c
jnc 0004h
dcr b
mov a,b
hltHere, you can replace 23h and 05h by any 8 bit number.
Prime_Coder
I'm a Wannabe Hacker
Re: Assembly language programing in 8086up......!!
Anybody here, will you please elaborate what the following code does?
I could guess that this code is for addition of 2 numbers, but what about that "str c" and all the next part? I couldn't understand that completely.
Anybody here, will you please elaborate what the following code does?
I could guess that this code is for addition of 2 numbers, but what about that "str c" and all the next part? I couldn't understand that completely.
Anish
Spectre
Re: Assembly language programing in 8086up......!!
yeah.. it will repeat sub c until the carry flag is set. And the carry flag is set when the number is no more divisible.
yeah.. it will repeat sub c until the carry flag is set. And the carry flag is set when the number is no more divisible.
Anish
Spectre
Re: Assemble language discussion thread
First understand how division is preformed in computers... To us all computer is a wonderful machine which does all sorts of work.. But actually, this machine knows nothing more than addition!. Subtraction is addition of negative numbers, multiplication is repeated addition, division is repeated addition of complementary dividend.
now, for example, what is 12/4?
answer is 3. we get it by a long hand division(remember grade 2 math)
but the computer does it some what like this:
takes 12 and calculates how many times 4 can be subtracted from it! its just simple as it is. 12-4=8(1 time) 8-4=4(2 times) 4-4=0(3 times). It can no longer subtract 4 from 0 with out carry. so it assumes the quotient to be 3.!
So, let me explain it line by line...
mvi a,23h - loads the a register with 23h
mvi c,05h - loads the c register with 05h
sub c - subtracts 05h from 23h and places the answer in a register
inr b - increments b register for each subtraction count of 05h from 23h
jnc 0004h - if the carry flag is not set, then it jumps to 4th memory location.
dcr b - this is for adjusting the calculation
mov a,b - This is needed just to move the answer to a register.
hlt - stops the program.
First understand how division is preformed in computers... To us all computer is a wonderful machine which does all sorts of work.. But actually, this machine knows nothing more than addition!. Subtraction is addition of negative numbers, multiplication is repeated addition, division is repeated addition of complementary dividend.
now, for example, what is 12/4?
answer is 3. we get it by a long hand division(remember grade 2 math)
but the computer does it some what like this:
takes 12 and calculates how many times 4 can be subtracted from it! its just simple as it is. 12-4=8(1 time) 8-4=4(2 times) 4-4=0(3 times). It can no longer subtract 4 from 0 with out carry. so it assumes the quotient to be 3.!
So, let me explain it line by line...
mvi a,23h - loads the a register with 23h
mvi c,05h - loads the c register with 05h
sub c - subtracts 05h from 23h and places the answer in a register
inr b - increments b register for each subtraction count of 05h from 23h
jnc 0004h - if the carry flag is not set, then it jumps to 4th memory location.
dcr b - this is for adjusting the calculation
mov a,b - This is needed just to move the answer to a register.
hlt - stops the program.