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GO Classes DPP | COMPILER|COMPILATION PHASES

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3 3 votes

Consider the following snippet of C code

int main() { /* Line 1 */
    int a = 5, b = 10; /* Line 2 */
    if (a < b) then { /* Line 3 */
        a = a + 1; /* Line 4 */
    }
}


Identify the compiler's primary response during the compilation process:

  1. NO COMPILATION ERROR
     
  2. A LEXICAL ERROR
     
  3. A SYNTACTIC ERROR
     
  4. A SEMANTIC ERROR

3 Answers

3 3 votes

LEXICAL ANALYSIS: The scanner looks at the word $\verb|then|$. In many languages (like Pascal or Basic), $\verb|then|$ is a valid keyword. In C, the scanner simply sees the characters $\verb|t-h-e-n|$ and identifies them as a valid identifier (like a variable name). Since it is a valid sequence of characters, there is no Lexical Error.

Syntax ANALYSIS: $\verb|if(a < b) then }|$ is not a valid syntax

Either $\verb|{ }|$ should come immediately after if or there should be semicolon after then

Hence it will generate syntactic error

Correct option: C

0 0 votes

in Line 3 , then will be interpreted by lexical analysis as indentifiers
so it pass lexical analysis
in syntax analysis , it used  CFG to make it make no sense there so it throws error 
hence it is syntax error

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