Question

Consider the following statements:
$S_1:$ Purpose of using intermediate code in compilers is to improve the register allocation.
$S_2:$ Operator grammer allows unit production .
$S_3:$ Directed acyclic graph can be used to eliminate the common sub expression
which of the above statements is / are correct?

• A. All $S_1,S_2$ , $S_3$ only
• B. $S_{1}and{S}_2$ only
• C. $S_{2}and{S}_3$ only
• D. $S_{1}and{S}_3$ only

Answer 1

The correct option is C $S_{2}and{S}_3$ only

$S_1$ : Intermediate code generation enhances the portability of the code . $S_1$ is incorrect .
$S_2$ : Operator grammer allows unit production . It has following restriction.
Two nonterminal should not adjacent
Null production {$A\to ϵ$ } is not allowed in the grammer .
$S_3$: Directed acyclic graph is used to eliminate common sub expression .
Both $S_2$ amd $S_3$ is correct.