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Hey Princess8086 Programs

Sunday 9 October 2011



Shorting (Descending Order)

9 8 7 6 5 4 3 2 1




AX BX CX SI

Registers Used in this program

AX and BX Registers are used to do the arithmatic operations

CX is the count register ( to keep count of how many numbers are there totally )

SI is the register which holds the address of the memory locations where we are giving the data as

input




Program Code Lets Start with Lines 1 and 2 and 4Line 1 initializes the value 0 in AX Register

Line 2 Puts the value 0003H which is hexadecimal for 3 in the BX register

this value is used as a count value, in this program we’re going to sort 3elements hence we save 3 in BX

In line 4 we are putting the value 3 into the CX register also,

because in 8086 the loop instruction depends on the CX

register... if the value of CX is not 0 then the loop instruction

will jump to whatever part of the code that is assigned to it

For Example

loop START

this means jump to the part of the program that is labelled START

which in this case is line no. 6

this jump will only happen if the value of CX is not 0... if the value of

CX is 0 then the line loop START doesnt do anything

We use this to our advantage... so now since CX = 3 we can assume that

all the loop instructions will be performed 3 times at least...

the loop instruction is a combination of 2 instructions

1. decrement CX

2. jump to other part of code

AX BX CX

0000H 0003H 0003H




Program Code

AX BX CX

74 0003H 0003H

Line 5 moves the value 1200H to SI .... now 1200H is the starting address of the data in

the memory location.

Line 6 moves the data stored in 1200H to the AX Register

SI

1200H

1200H

1202H

74

FF

And sweetie lets assume we have entered

the values 74 and FF in the memory

location 1200H and 1202H

notice we dont store anything in 1201H

because the data we are handling is 16 bit

and 1200H is an 8bit memory location so

the processor automatically uses both

1200H and 1201H to store the 16bit data

1200H(8bit) + 1201H(8bit)




Program Code

AX BX CX

74 0003H 0003H

Line 7 is going to compare AX, and [SI + 2]

In the previous slide we moved SI value to AX that means AX now has 74

then we compare the value of AX with [SI + 2] since SI is 1200H that means SI + 2 =1202H which basically corresponds to the next memory location and the data there is FF

SI

1200H

1200H

1202H

74

FFcomparing




Program Code

AX BX CX

74 0003H 0003H

Line 8 JNG -> Jump if not greater

this line simply see’s the result of the previous step and if the value stored in [SI + 2] is

not greater than the vaulue stored in AX then jump to LOOP1

In our example FF stands for 255 ok in decimal.. so we’re comparing FF with 74 and as we

can see FF is definitely greater than 74 so the jump does not take place

SI

1200H

1200H

1202H

74

FFcomparing




Program Code

AX BX CX

74 0003H 0003H

Line 9 and 10

This is very simple... XCHG is the instruction for Exchange basically it swaps the value of

the 2 operands given to it.

Ex:

Lets say AX has 27 and BX has 58

XCHG AX, BX

so this will put what ever value is there in BX to AX

and the value of AX to BX

So now AX will have 58 and BX will have 27

SI

1200H

1200H

1202H

74

FFcomparing




Program Code

AX BX CX

0003H 0003H

Line 9 and 10

So now in line 9 the value of AX is put in SI +2and the value of SI + 2 is in AX

As shown in below diagram

SI

1200H

1200H

1202H74

FF

74




Program Code

AX BX CX

0003H 0003H

Line 9 and 10

And in line 10 the value of AX and SI are exchanged so..

AX will have 74 now

and SI will have FF

SI

1200H

1200H

1202H

74

FF

74




Program Code

AX BX CX

0003H 0003H

Line 11

Now we go to line 11 where 0002H (hex for 2) is added to SI.. which means SI now

points to 1202H

SI

1202H

1200H

1202H

74

FF

74




Program Code

AX BX CX

0003H 0003H

Line 12 and 13

line 12 loop start.. this instruction decrements the value of CX and jumps to the program

location START

line 13 this instrution decrements BX

SI

1202H

1200H

1202H

74

FF

74




Program Code

AX BX CX

0003H 0003H

Line 12 and 13

line 12 loop start.. this instruction decrements the value of CX and jumps to the program

location START

line 13 this instrution decrements BX

line 14 jump if not zero jnz to STOP

life 15 hlt

SI

1202H

1200H

1202H

74

FF

74


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