![Arithmetic Instructions
• ADD Des, Src:
• It adds a byte to byte or a word to word.
• It effects AF, CF, OF, PF, SF, ZF flags.
• E.g.:
• ADD AL, 74H
• ADD DX, AX
• ADD AX, [BX]](https://image.slidesharecdn.com/arithmeticinstrctions-200319141115/85/Arithmetic-instrctions-2-320.jpg)
![Arithmetic Instructions
• ADC Des, Src:
• It adds the two operands with CF.
• It effects AF, CF, OF, PF, SF, ZF flags.
• E.g.:
• ADC AL, 74H
• ADC DX, AX
• ADC AX, [BX]](https://image.slidesharecdn.com/arithmeticinstrctions-200319141115/85/Arithmetic-instrctions-3-320.jpg)
![Arithmetic Instructions
• SUB Des, Src:
• It subtracts a byte from byte or a word from
word.
• It effects AF, CF, OF, PF, SF, ZF flags.
• For subtraction, CF acts as borrow flag.
• E.g.:
• SUB AL, 74H
• SUB DX, AX
• SUB AX, [BX]](https://image.slidesharecdn.com/arithmeticinstrctions-200319141115/85/Arithmetic-instrctions-4-320.jpg)
![Arithmetic Instructions
• SBB Des, Src:
• It subtracts the two operands and also the
borrow from the result.
• It effects AF, CF, OF, PF, SF, ZF flags.
• E.g.:
• SBB AL, 74H
• SBB DX, AX
• SBB AX, [BX]](https://image.slidesharecdn.com/arithmeticinstrctions-200319141115/85/Arithmetic-instrctions-5-320.jpg)
![• Operation Performed :--
– If source is byte then AX AL * unsigned 8 bit
source
– If source is word then DX, AX AX * unsigned 16
bit source
Examples :--
1. MUL BL ; Multiply AL by BL & the result in AX
2. MUL CX ; Multiply AX by CX & the result in DX,AX
3. MUL Byte PTR [SI] ; AX AL * [SI]
MUL (Unsigned multiplication) Contd..](https://image.slidesharecdn.com/arithmeticinstrctions-200319141115/85/Arithmetic-instrctions-19-320.jpg)
![• Operation Performed :--
– If source is byte then AX AL * signed 8 bit
source
– If source is word then DX, AX AX * signed 16 bit
source
Examples :--
1. IMUL BL ; Multiply AL by BL & the result in AX
2. IMUL CX ; Multiply AX by CX & the result in DX,AX
3. IMUL Byte PTR [SI] ; AX AL * [SI]
IMUL (Signed multiplication) Contd..](https://image.slidesharecdn.com/arithmeticinstrctions-200319141115/85/Arithmetic-instrctions-23-320.jpg)
![Examples :--
1. DIV BL ; Divide word in AX by byte in
BL, Quotient in AL, remainder
in AH.
2. DIV CX ; Divide double word in DX:AX
by word in CX, Quotient in AX,
Remainder in DX.
3. DIV [BX] ; Divide word in AX by byte in
memory location pointer by
BX.
DIV (Unsigned Division)Contd..](https://image.slidesharecdn.com/arithmeticinstrctions-200319141115/85/Arithmetic-instrctions-28-320.jpg)
![Examples :--
1. IDIV BL ; Divide signed word in AX by
signed byte in BL, Quotient in
AL, remainder in AH.
2. IDIV CX ; Divide signed double word in
DX:AX by signed word in CX,
Quotient in AX, Remainder in
DX.
3. IDIV [BX] ; Divide signed word in AX by
signed byte in memory
location pointer by BX.
IDIV (Signed Division)Contd..](https://image.slidesharecdn.com/arithmeticinstrctions-200319141115/85/Arithmetic-instrctions-37-320.jpg)
Arithmetic instrctions
- 2. Arithmetic Instructions • ADD Des, Src: • It adds a byte to byte or a word to word. • It effects AF, CF, OF, PF, SF, ZF flags. • E.g.: • ADD AL, 74H • ADD DX, AX • ADD AX, [BX]
- 3. Arithmetic Instructions • ADC Des, Src: • It adds the two operands with CF. • It effects AF, CF, OF, PF, SF, ZF flags. • E.g.: • ADC AL, 74H • ADC DX, AX • ADC AX, [BX]
- 4. Arithmetic Instructions • SUB Des, Src: • It subtracts a byte from byte or a word from word. • It effects AF, CF, OF, PF, SF, ZF flags. • For subtraction, CF acts as borrow flag. • E.g.: • SUB AL, 74H • SUB DX, AX • SUB AX, [BX]
- 5. Arithmetic Instructions • SBB Des, Src: • It subtracts the two operands and also the borrow from the result. • It effects AF, CF, OF, PF, SF, ZF flags. • E.g.: • SBB AL, 74H • SBB DX, AX • SBB AX, [BX]
- 6. Arithmetic Instructions • INC Src: • It increments the byte or word by one. • The operand can be a register or memory location. • It effects AF, OF, PF, SF, ZF flags. • CF is not effected. • E.g.: INC AX
- 7. Arithmetic Instructions • DEC Src: • It decrements the byte or word by one. • The operand can be a register or memory location. • It effects AF, OF, PF, SF, ZF flags. • CF is not effected. • E.g.: DEC AX
- 8. DAA (Decimal Adjust Accumulator) Syntax :-- DAA • This instruction is used to convert the result of the addition of two packed BCD numbers to a valid BCD number. • The result has to be only in AL. • After addition if the lower nibble is greater than 9 or AF =1, it will add 06H to the lower nibble in AL. • After this addition, if the upper nibble is greater than 9 or if CF = 1, DAA instruction adds 60H to AL. • DAA instruction affects AF,CF,PF and ZF. OF is undefined.
- 9. DAA Instruction contd.. • Operation Performed :-- – If lower nibble of AL > 9 or AF =1 then AL = AL +06 – If higher nibble of AL > 9 or CF =1 then AL = AL +60
- 10. Numeric Examples AL = 53H, CL = 29H ADD AL,CL ; AL (AL) + (CL) ;AL 53 + 29 ;AL 7CH DAA ; AL 7C +06 (as C>9) ;AL 82
- 11. Numeric Examples AL = 73H, CL = 29H ADD AL,CL ; AL (AL) + (CL) ;AL 73 + 29 ;AL 9CH DAA ; AL 02 and CF = 1 (as C>9)
- 12. DAS (Decimal Adjust After Subtraction) Syntax :-- DAS • This instruction is used to convert the result of the subtraction of two packed BCD numbers to a valid BCD number. • The subtraction has to be only in AL. • After subtraction if the lower nibble is greater than 9 or AF =1, it will subtract 06H from the lower nibble in AL. • If the result of the subtraction sets the carry flag or if the upper nibble is greater than 9, DAS instruction subtracts 60H from AL. • DAS instruction affects AF,CF,PF and ZF. OF is undefined.
- 13. DAS Instruction contd.. • Operation Performed :-- – If lower nibble of AL > 9 or AF =1 then AL = AL -06 – If higher nibble of AL > 9 or CF =1 then AL = AL -60
- 14. Numeric Examples AL = 75, BH = 46 SUB AL,BH ; AL (AL) - (BH) ;AL 75 - 46 ;AL 2FH ; AF = 1 DAS ; AL 2F - 06 (as F>9) ;AL 29
- 15. Numeric Examples AL = 38, BH = 61 SUB AL,BH ; AL (AL) - (BH) ;AL 38 - 61 ;AL D7H ; CF = 1 DAS ; AL D7 - 60 (as D>9) ;AL 77
- 16. NEG ( Negate ) Syntax :-- NEG destination • This instruction replaces the number in the destination with the 2’s complement of that number. • For obtaining the 2’s complement, it subtracts the contents of destination from zero. •The result is stored back in the destination which may be a register or a memory location • If OF =1, it indicates that the operation could not be completed successfully. • NEG instruction affects all conditional flags.
- 17. MUL (Unsigned multiplication) Syntax :-- MUL source • This instruction multiplies an unsigned byte from source with an unsigned byte in AL register or unsigned word from source with an unsigned word in AX register. • The source can be a register or memory location but cannot be an immediate data.
- 18. MUL (Unsigned multiplication) Contd.. •When a byte is multiplied with a byte in AL, the result is stored in AX. • When a word is multiplied with a word in AX, the MSW (Most Significant Word ) of the result is stored in DX and the LSW (Least Significant Word ) of the result is stored in AX. • If MS Byte or Word of the result is zero, CF and OF both will be set. •All other flags are modified depending upon the result
- 19. • Operation Performed :-- – If source is byte then AX AL * unsigned 8 bit source – If source is word then DX, AX AX * unsigned 16 bit source Examples :-- 1. MUL BL ; Multiply AL by BL & the result in AX 2. MUL CX ; Multiply AX by CX & the result in DX,AX 3. MUL Byte PTR [SI] ; AX AL * [SI] MUL (Unsigned multiplication) Contd..
- 20. IMUL (Signed multiplication) Syntax :-- IMUL source • This instruction multiplies a signed byte from source with a signed byte in AL register or signed word from source with an signed word in AX register. • The source can be a register, general purpose, base or index, or memory location, but cannot be an immediate data.
- 21. IMUL (Signed multiplication) Contd.. •When a byte is multiplied with a byte in AL, the result is stored in AX. • When a word is multiplied with a word in AX, the MSW (Most Significant Word ) of the result is stored in DX and the LSW (Least Significant Word ) of the result is stored in AX.
- 22. IMUL (Signed multiplication) Contd.. •If the magnitude of the product does not require all the bits of the destination, the unused bits are filled with copies of the sign bit. •If AH and DX contain parts of the 16 & 32 bit results, CF and OF are set, If the unused bits are filled by the sign bit, OF and CF are cleared.
- 23. • Operation Performed :-- – If source is byte then AX AL * signed 8 bit source – If source is word then DX, AX AX * signed 16 bit source Examples :-- 1. IMUL BL ; Multiply AL by BL & the result in AX 2. IMUL CX ; Multiply AX by CX & the result in DX,AX 3. IMUL Byte PTR [SI] ; AX AL * [SI] IMUL (Signed multiplication) Contd..
- 24. DIV (Unsigned Division) Syntax :-- DIV source • This instruction divides an unsigned word (16Bits) in AX register by an unsigned byte (8Bits) from source or an unsigned double word (32 bits) in DX & AX register by an unsigned word (16bits) from source • The source can be a register or memory location but cannot be an immediate data.
- 25. DIV (Unsigned Division)Contd.. •When a word in AX is divided by a byte, AL will contain the 8 bit quotient and AH will contain an 8 bit remainder. • When a double word in DX (MSW) & AX (LSW) is divided by a word, AX will contain the 16 bit quotient and DX will contain an 16 bit remainder.
- 26. DIV (Unsigned Division)Contd.. •If a byte is to be divided by a byte, AL is loaded with dividend and AH is filled with all 0’s. •If a word is to be divided by a word, Ax is loaded with dividend and DX is filled with all 0’s. •If an attempt is made to divide by 0, or the quotient is too large (FF or FFFF), type 0 interrupt is generated. •No flags are affected.
- 27. • Operation Performed :-- –If source is byte then • AL AX / unsigned 8 bit source ; (quotient) • AH AX MOD unsigned 8 bit source ; (remainder) –If source is word then • AX DX:AX / unsigned 16 bit source ; (quotient) • DX DX:AX MOD unsigned 16 bit source ; (remainder) DIV (Unsigned Division)Contd..
- 28. Examples :-- 1. DIV BL ; Divide word in AX by byte in BL, Quotient in AL, remainder in AH. 2. DIV CX ; Divide double word in DX:AX by word in CX, Quotient in AX, Remainder in DX. 3. DIV [BX] ; Divide word in AX by byte in memory location pointer by BX. DIV (Unsigned Division)Contd..
- 29. CBW (Convert Signed Byte to Word) Syntax :-- CBW • This instruction converts a signed byte to a signed word. •This instruction copies the sign of a byte in AL to all the bits in AH. • AH is then said to be the sign extension of AL. •CBW operation is done before performing division of a signed byte in the AL by another signed byte with IDIV instruction.
- 30. CBW (Convert Signed Byte to Word) contd.. Operation :-- • AH filled with 8th bit of AL i.e., D7 This does not affect any flags. Example :-- If AX = 009BH, (00000000 10011011 After CBW Instruction, AX =FF9B (11111111 10011011)
- 31. CWD (Convert Signed Word to Double Word) Syntax :-- CWD • This instruction copies the sign bit of a word in AX to all the bits in DX. • Thus the sign of AX is said to be extended to DX. •CWD operation is done before performing division of a signed word in the AX by another signed word with IDIV instruction.
- 32. CWD (Convert Signed Word to Double Word) contd.. Operation :-- • DX filled with 16th bit of AX i.e., D15 This does not affect any flags. Example :-- If DX = 0000H (00000000 00000000) If AX = F0C7H, (11110000 11000111) After CWD Instruction, DX = FFFFH (11111111 11111111) AX =F0C7 (11110000 11000111)
- 33. IDIV (Signed Division) Syntax :-- IDIV source • This instruction divides an signed word (16Bits) in AX register by an signed byte (8Bits) from source or An signed double word (32 bits) in DX & AX register by an signed word (16bits) from source • The source can be a register or memory location but cannot be an immediate data.
- 34. IDIV (Signed Division)Contd.. •When a word in AX is divided by a byte, AL will contain the 8 bit quotient and AH will contain an 8 bit remainder. • When a double word in DX (MSW) & AX (LSW) is divided by a word, AX will contain the 16 bit quotient and DX will contain an 16 bit remainder.
- 35. IDIV (Signed Division)Contd.. •If a byte is to be divided by a byte, AL is loaded with dividend and AH is filled with all 0’s. •If a word is to be divided by a word, Ax is loaded with dividend and DX is filled with all 0’s. •If an attempt is made to divide by 0, or the quotient is too large (FF or FFFF), type 0 interrupt is generated. •No flags are affected.
- 36. • Operation Performed :-- –If source is byte then • AL AX / unsigned 8 bit source ; (quotient) • AH AX MOD unsigned 8 bit source ; (remainder) –If source is byte then • AX DX:AX / unsigned 16 bit source ; (quotient) • DX DX:AX MOD unsigned 16 bit source ; (remainder) IDIV (Signed Division)Contd..
- 37. Examples :-- 1. IDIV BL ; Divide signed word in AX by signed byte in BL, Quotient in AL, remainder in AH. 2. IDIV CX ; Divide signed double word in DX:AX by signed word in CX, Quotient in AX, Remainder in DX. 3. IDIV [BX] ; Divide signed word in AX by signed byte in memory location pointer by BX. IDIV (Signed Division)Contd..
- 38. Example of division of a signed byte with signed byte :-- MOV BL,divisor ; Load signed byte divisor in BL MOV AL,dividend ; Load signed byte dividend in AL CBW ;Extend sign of AL into AH IDIV BL ; Byte division, Remainder in AH and quotient in AL