GATE Solved Paper 2017-19 - GATE 2017 Shift 1

62. Consider the expression (a-1) * ((( b + c ) / 3 ) + d) Let X be the minimum number of registers required by an optimal code generation (without any register spill) algorithm for a load/store architecture in which
(i) only loads and store instructions can have memory operands and
(ii) arithmetic instructions can have only register or immediate operands.
The value of X is _____.

  • Option : A
  • Explanation :

    The given expression is (a-1) * ((( b + c ) / 3 ) + d)
    The optimal generated code is:
    Load R1, b       R1 ⟵ b
    Load R2, c       R2 ⟵ c
    ADD R1, R2      R1 ⟵ R1 + R2
    Div R1, 3       R1 ⟵ R1/3
    Load R2, d       R2 ⟵ d
    Add R1, R2       R1 ⟵ R1 + R2
    Load R2, a       R2 ⟵ a
    Sub R2, 1       R2 ⟵ R2 - 1
    Mul R2, R1       R2 ⟵ R2 * R1
    Hence minimum 2 registers required.
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65. Consider a database that has the relation schema CR (StudentName, CourseName). An instance of the schema CR is as given below.

CR
Student NameCourse Name
SACA
SACB
SACC
SBCB
SBCC
SCCA
SCCB
SCCC
SDCA
SDCB
SDCC
SDCD
SECD
SECA
SECB
SFCA
SFCB
SFCC
The following query is made on the database.
T1 ← πCourseNameStudentName=’SA’(CR))
T2 ← CR ÷ T1
The number of rows in T2 is ________.

Note – Numerical Type question

  • Option : C
  • Explanation :
    Explanation: Result of T1:
    CA
    CB
    CC

    Result of T2 = CR/T1
    SA
    SC
    SD
    SF
    Total = 4
    Therefore, option C is correct

    Alternate Solution :
    The output of query T1 will be the courses enrolled by student SA i.e CA, CB, CC
    The output of query T2 will be the names of the students who enroll all the courses that are the output of query T1 (division operator) i.e CA, CB, CC
    From the table we can see that SA, SC, SD, SF have enrolled all the courses so the output of T2 will have 4 row
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