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Introduction to Bioinformatics - North South University(2)

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					    Lecture 5

    Presented By
 Dr. Shazzad Hosain
Asst. Prof. EECS, NSU
                     Agenda
• Logic Instructions
    – AND, OR, XOR and NOT
•   TEST Instruction
•   Shift and Rotate Instructions
•   Stack Operations
•   Introduction to Procedures
    AND, OR and XOR Instructions
AND destination, source
OR destination, source
XOR destination, source

• Memory-to-memory operations are not allowed
• Effect on flags
   – SF, ZF, PF reflect the result
   – AF is undefined
   – CF, OF = 0
        Use of Logic Instructions
• Selectively modify the bits of destination
   – b AND 1 = b          (b represents a bit, 0/1)
   – b AND 0 = 0
   – b OR 0 = b
   – b OR 1 = 1
   – b XOR 0 = b
   – b XOR 1 = ~b         (complement of b)
• So, AND cab be used to clear specific destination bit
• OR can be used to set specific destination bit
• XOR can be used to complement specific destination bit
                       Examples
Example 7.2: Clear the sign bit of AL while leaving the
  other bits unchanged.
  AND        AL, 7Fh           0111 1111 = 7Fh

Example 7.3: Set the msb and lsb of AL while preserving
  the other bits.
  OR         AL, 81h           1000 0001 = 81h

Example 7.4: Change the sign bit of DX
  XOR        DX, 8000h
            NOT Instruction
Complement operation

          NOT destination


Example 7.5: Complement the bits in AX
          NOT AX
                     Agenda
• Logic Instructions
    – AND, OR, XOR and NOT
•   TEST Instruction
•   Shift and Rotate Instructions
•   Stack Operations
•   Introduction to Procedures
               TEST Instruction
• TEST performs AND on the destination
• TEST destination, source
• Effects on flags
  – SF, ZF, PF reflect the result
  – AF is undefined
  – CF, OF = 0
• TEST vs. CMP
  – CMP is subtraction operation
                   TEST Example
• Jump to label BELOW if AL contains an even
  number

           TESET    AL, 1   ; is AL even?
           JZ       BELOW   ; yes, go to BELOW
                     Agenda
• Logic Instructions
    – AND, OR, XOR and NOT
•   TEST Instruction
•   Shift and Rotate Instructions
•   Stack Operations
•   Introduction to Procedures
     Shift and Rotate Instructions
• Two types of shift and rotate instructions
   – Logical Shift / Rotate
   – Arithmetic Shift/Rotate
• Both logical and arithmetic left shift are identical
• But right shifts are different
  Shift and Rotate Instructions
SHL       DH, 3    ; DH = 1110 1111   SHR       DH, 3    ; DH = 1110 1111

      DH = 0111 1000    C=1                 DH = 0001 1101    C=1


SAL       DH, 2   ; DH = 1110 1111    SAR       DH, 2   ; DH = 1110 1111

      DH = 1011 1100    C=1                 DH = 1111 1011    C=1
Rotate Instructions



                 Let
                 DH = 8Ah = 1000 1010
                 CF = 1

                 After first RCR
                 DH = 1100 0101     CF = 0

                 After second RCR
                 DH = 0110 0010     CF = 1
                     Agenda
• Logic Instructions
    – AND, OR, XOR and NOT
•   TEST Instruction
•   Shift and Rotate Instructions
•   Stack Operations
•   Introduction to Procedures
               Stack vs. Queue
• Stack
  – LIFO : Last In First Out
• Queue
  – FIFO : First In First Out




                                Queue
                                        Stack
PUSH vs. POP in Stack
Stack Operations
PUSH Instructions
POP Instructions
Stack example
                     Agenda
• Logic Instructions
    – AND, OR, XOR and NOT
•   TEST Instruction
•   Shift and Rotate Instructions
•   Stack Operations
•   Introduction to Procedures
                      Procedure Example
Product = 0
REPEAT
  IF lsb of B is 1
  THEN
      product = product + A
  END_IF
  Shift left A
  Shift right B
UNTIL B = 0
                  References
• Ch 7, Assembly Language Programming – by
  Charls Marut
• Ch 4, Intel Microprocessors – by Brey

				
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