Given the following declarations, write a formula to locate any random record (e

Question

Given the following declarations, write a formula to locate any random record (e.g., base + offset) in the array evaluating all constants, i.e., calculate the actual physical memory address of the location of X(J) in memory for any -30 <= J <= 20. Assume the first unit of memory assigned by the translator is at location Lo (base address). You need not do the actual arithmetic as long as you explicitly show/state all values/numbers required for the calculation and the formulas constituting your answer.

type MyType is record

            xAxis: array(-5..4) of character;

            yAxis: array(-5..4) of character;

            temperature: integer;

            airSpeed: character;

            chillFactor: float;

            locationt: Arrary(1..10) of character;

            label: Array(0..9) of character;

end record;

X: array(-30 .. 20) of MyType;

Explanation / Answer

Solution:

Given Base Address=Lo, -30 <= J <= 20.

To calculate the memory allocated to one MyType Record:

xAxis will take 10 bytes ,(10 locations to store characters)

yAxis will take 10 bytes , (10 locations to store characters)

temperature will take two bytes,(to store integer)

airSpeed will take 1 byte , (to store character)           

chillFactor: will take four bytes,(to store float)

locationt: will take 10 bytes ,(10 locations to store characters)

label: will take 10 bytes ,(10 locations to store characters)

Therefore one MyType Record will take 10+10+2+1+4+10+10 =47 bytes

X can store 51 records where each record size is 47bytes

To Access a record from X randomly, the formula will be

Physical Address=Lo +( ( ( J - 1) * 47) + 1) , where J =1,2..<= 20.

Physical Address=Lo + ( ( (J - 1)* 47) - 1) , where J>=-30 ,-29,28…,-1 , 0

For Example, to read 4th record J=4:

            Physical Address = Lo + ((4-1)*47 +1)

                                                = Lo + (3*47 +1)

                                                =Lo +(141+1)

Since 3 records can take 3*47 bytes =141 bytes, the 4th record will starts at 142 +Lo

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