The document describes various assembly language instructions, including their syntax and usage, such as zx for zero extension, sx for sign extension, inc for increment, dec for decrement, xchg for exchanging register values, and neg for negation. It also covers the functions of instructions like lahf and sahf for loading and shifting status flags, ptr for pointer operations, as well as lengthof, sizeof, type, and loop. Additionally, it includes a brief tribute to Arfa Karim Randhawa, the youngest Microsoft Certified Professional.

1. Assembly Language Instructions
By Didar Hussain

2. GENERAL SYNTAX
Include Irevine32.inc
.data
.code
Main proc
Call DumpRegs
Exit
Main ENDP
END main
By Didar Hussain 2
Data portion
Code portion

3. INSTRUCTIONS
 ZX
 SX
 INC
 DEC
 XCHG
 NEG
 LAHF
 SAHF
 PTR
 LENGTHOF
 SIZEOF
 TYPE
 LOOP
By Didar Hussain 3

4. ZX
 ZX instruction is used to extend zeros without the
values which we given
 For e.g when we give 11h in the al register, in
this condition without 11 all the values in the eax
register will be zeros
 In simple words there will be 6 leading zeros see
the following
00000011
By Didar Hussain 4

5. SYNTAX
.data
var byte 29h
.code
main proc
movzx eax,var
By Didar Hussain 5

6. PROGRAM
By Didar Hussain 6

7. SX
 Same to same ZX but there will be leading
ones
 For e.g we entered 84 using al register and we
want to replace garbage values of ah and
extended portion with 1, for this type of task
we use SX instruction
 Note that when the MSB in any number is one
then SX create leading 1,s otherwise it create
leading 0,s.
By Didar Hussain 7

8. SYNTAX
.data
var byte 89h
.code
main proc
movsx eax,var
By Didar Hussain 8

9. PROGRAM
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10. INCREMENT
 For increment instruction simply use inc
 Through this instruction a number is
incremented
 For e.g when we give 25 through using of inc
instruction it become 26
 In simple words it added 1 to a number
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11. SYNTAX
.data
var byte 85h
.code
main proc
mov al,var
inc al
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12. PROGRAM
By Didar Hussain 12

13. DECREMENT
 For decrement instruction simply use dec
 It is completely opposite of increment instruction
 Through this instruction a number is decremented
 So in simple words we can say it subtract 1 from a
number
 For e.g 45 become 44, 12 become 11 through using
dec instruction
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14. .data
var byte 85h
.code
mov al,var
dec al
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SYNTAX

15. PROGRAM
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16. XCHG
 XCHG stands for xchange
 It is used to exchange two register with each other
 For e.g al and ah are two register which store different
values i-e al store 14 and ah store 13
 We want that these register xchange values with each
other i-e al store 13 and ah store 14
 So this type of operations we can done with the help
of XCHG instruction
16By Didar Hussain

17. SYNTAX
.code
main proc
mov al,14h
mov ah,13h
xchg al,ah
By Didar Hussain 17

18. PROGRAM
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19. NEG
 Neg stands for negative
 As express from name it is used to convert a positive
number into negative
 We also can say it convert unsigned into signed
 Note that the signed and unsigned operations depends
on only most significant bit(msb).
 When msb=1 it represent -ve/signed, and when msb=0
it represent +ve/unsigned
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20. SYNTAX
.data
var dword 70000000h
.code
main proc
mov eax,var
neg eax
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21. PROGRAM
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22. LAHF
 LAHF stands for load status flag into ah register
 The LAHF instruction is used for to move the
status of flags into ah register
 And then we move the ah register into memory
 So the main purpose of LAHF is to move the flag
status into memory
By Didar Hussain 22

23. SYNTAX
.data
var byte ?
.code
main proc
mov al,11111111b
add al,00000001b
lahf
mov bl,11110000b
add bl,00001111b
By Didar Hussain 23

24. PROGRAM
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25. SAHF
 SAHF stands for shift status flags into ah register
 It is used to move the status of flags again from
memory to ah register
 It is basically perform a work completely opposite of
LAHF
 LAHF move the flags status to memory and SAHF
shift the flags status again from memory to register
By Didar Hussain 25

26. SYNTAX
.data
var byte ?
.code
main proc
mov al,11111111b
add al,00000001b
lahf
mov bl,11110000b
add bl,00001111b
sahf
By Didar Hussain 26

27. PROGRAM
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28. PTR
 Ptr stands for pointer
 Ptr is used to move small values to a big register or
large values to a small register.
 Normally it is don't possible to done this type of
operations but through the help of ptr instruction
we can easily perform
 We write as byte ptr,word ptr,dword ptr.
By Didar Hussain 28

29. PTR
 Byte ptr in that condition when there is a large values
for e.g word or dword we want to store in al register
 Word ptr in that condition when there is a large values
i-e dbyte or small values i-e byte we want to store in
ax register .
 Similarly when small values i-e byte or word we
want to store in eax register then we use dword ptr
By Didar Hussain 29

30. SYNTAX
.data
var byte 24h
.code
mov eax,dword ptr var
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31. PROGRAM
By Didar Hussain 31

32. • The lengthof instruction is used to find the number
of elements
• The elements which we entered during coding in
any register using any number system
• When we want to find how many elements we
entered, for this purpose we use the lengthof
instruction
By Didar Hussain 32
LENGTHOF

33. .data
var1 word 45h,98h,78h
.code
main proc
mov al,lengthof var1
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SYNTAX

34. PROGRAM
By Didar Hussain 34

35. SIZEOF
 The sizeof instruction is used to find the complete size of
a register
 In simple words the sizeof instruction used to find that
”how many size is of the register”
 Note that sizeof mean the register size should be
multiplied with the number of elements
 Sizeof we can simply find by the following formula
Sizeof=register size multiplied by number of elements
 Register size mean al/byte register is one byte, ax/word is
two bytes and eax/dword is 4 bytes
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36. SYNTAX
.data
var word 20h,54h,62h,78h
.code
main proc
mov al,sizeof var
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37. PROGRAM
Output
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38. TYPE
 Type instruction is used to show the status of the
register
 For e.g al register or byte contain one byte, it show
1,ax register or word contain two bytes so it show
2,similarly eax register or dword contain 4 bytes so it
show 4
 In simple words the type instruction show or find out
the number of bytes in the given register
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39. SYNTAX
.data
var byte 68h
.code
main proc
mov al,type var
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40. PROGRAM
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41. LOOP
 Loop is basically a counter
 Counter mean repetition of a statement for a
specific condition
 A statement continue until a condition occur
 So with the help of loop we can get a
condition which we want
 It is to be noted that for LOOP a counter
register is used
By Didar Hussain 41

42. SYNTAX
.code
main proc
mov ecx,6
mov eax,2
L:
inc eax //6 times 2 will be incremented, so 2 well becomes 8
loop L
By Didar Hussain 42

43. PROGRAM
By Didar Hussain 43

44. Youngest Microsoft
Certified Professional
 Arfa Karim Randhawa
 1995-2012
 She became the world youngest Microsoft Certified Professional at the age of nine
 In 2011, she suffered a cardiac arrest and she died in 2012, at the age of 16
“If you think shy, you act shy.
If you think confident you act confident”.
Arfa Karim
44
A True Inspiration
By Didar Hussain

45. THANKS
By Didar Hussain 45