Assignment statement and Arithmetic operation 2 +–×÷ Expressions and Operations

Expression Y A+B ; := NO, this is an EXPRESSION Let’s consider the following statement. Y A+B ; := Is it an EQUATION?

Expression OPERATOR ; A+B := Y OPERANDS

Expression Expression looks like a mathematical expression. The computer first evaluate the expression and the result will be stored in the variable on the left hand side

3+4+5 A+B*C/D (A+B)*(A+B)/(B-C) A*X*X+B*X+C Pi*RADIUS*RADIUS Here are some examples of expressions: 3+4+5 A+B*C/D (A+B)*(A+B)/(B-C) A*X*X+B*X+C Pi*RADIUS*RADIUS 4*A*A-Pi*A*A A+(N-1)*D

Addition + integer + integer => integer real + integer => real integer + real => real real + real => real

Subtraction – integer - integer => integer real - integer => real integer - real => real real - real => real

Multiplication * integer * integer => integer real * integer => real integer * real => real real * real => real

Real Division / integer / integer => real real / integer => real real / real => real

Integer operations (DIV and MOD) Quotient 5 3 16 15 1 Remainder 16 MOD 3

Integer Division integer DIV integer => integer real DIV integer => NOT ALLOWED integer DIV real => NOT ALLOWED real DIV real => NOT ALLOWED

Modulo integer MOD integer => integer real MOD integer => NOT ALLOWED integer MOD real => NOT ALLOWED real MOD real => NOT ALLOWED

Exercise 2 If A, B, C are integer variables, and D, E, F are real variables, which of the following statements are invalid? 1. C:=A+B-C VALID 2. C:=D+E-F; INVALID 3. A:=C/B - C/B; INVALID 4. E:=(A+B) / (A+B) VALID 5. D:= D DIV D INVALID 6. A:= A MOD A VALID 7. D:=A+A+B+B+C+C; VALID

A := 3 + 4 * 5; Precedence Please consider the following Add statement or Multiply first? A := 3 + 4 * 5;

Precedence ( ) - (unary minus) * , / , MOD, DIV +, - In PASCAL, the precedence is: ( ) - (unary minus) * , / , MOD, DIV +, -