Boolean expressions .

. Consider E E₁ and M E ₂

- if E ₁ is false then E is also false so statements in E₁ .falselist become part of E.falselist

- if E₁ is true then E₂ must be tested so target of E₁ .truelist is beginning of E₂

- target is obtained by marker M

- attribute M.quad records the number of the first statement of E₂ .code

truelist and faliselist are synthesized attributes. if E ₁is false then E is also false so statements in E₁.falselist become part of E.falselist. And if E₁ is true then E₂ must be tested so target of E ₁.truelist is beginning of E ₂ . The target of E₁ .truelist is obtained from the marker M with the help of M.quad which records the number ( position) of the first statement of E ₂ .code because if E₁ is true then the code flow will depend on E ₂ .