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

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

3. Expression
OPERATOR ;
A+B := Y
OPERANDS

4. 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

5. 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

6. Addition + integer + integer => integer real + integer => real
integer + real => real
real + real => real

7. Subtraction – integer - integer => integer
real - integer => real
integer - real => real
real - real => real

8. Multiplication * integer * integer => integer
real * integer => real
integer * real => real
real * real => real

9. Real Division / integer / integer => real real / integer => real
real / real => real

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

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

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

13. 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

14. A := 3 + 4 * 5; Precedence Please consider the following Add statementor
Multiply first?
A := * 5;

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