Assignment Statements

variable = expression;

Expression can involve multiple operators: *, /, +, -

The expression is always evaluated first and then its value 
is assigned to the variable on the left.

Rules for evaluation (like Algebra)

subexpressions inside parentheses are evaluated separately

operators are evaluated according to the hierarchy:
unary +, - 
*, /, % (remainder division) 
binary +, -

Operators in same expression and at same precedence level 
are evaluated in left to right order. (Exception: unary 
operators in right to left order- Multiple unary operators are 
extremely rare!).

-b + c/d
-5.0 + 2.0 * 6.0      Operators are evaluated in order: _, _, _
				value is ?

-b / c * d
-5.0 / 2.0 * 6.0     Operators are evaluated in order: _, _,_,
value is ?

Integer division versus real division

The value of 5 / 2  (/ divides 2 integers) is different from 
the value of 5.0 / 2.0   (/ divides 2 reals).

5 / 2 is 2;		5.0 / 2.0 is 2.5

For 5 / 2.0 or 5.0 / 2, the integer is “promoted” to a real 
number and / divides 5.0 and 2.0 yielding 2.5. This happens 
because the operands of an arithmetic operator must both 
be the same type.

3.0 + 5 / 2	Operators are evaluated in order: _, _
			Value is ?

3.0 * 5 / 2	Operators are evaluated in order: _, _
			Value is ?

3 * 5 / 2		Operators are evaluated in order: _, _
			Value is ?


Mixed assignment

int m, n;
double x;

m = 15;  n = 10;
x = m / n;

What is value of x?  


(Note the expression is evaluated first, then the assignment 
takes place. / means integer division because both its 
operands are type int.)

m = 15;  x = 1.5;
n = m + x;

What is the value of n?

Operator % - remainder operator

Both operands must be integers or type int

15 % 10 yields the integer remainder of 15 divided by 10.

Value is __

10 % 15,  value is __

4 % 3,  value is ___
7 % 3,  value is ___

9 % 2,  value is ___
10 % 2,  value is ___
11 % 2, value is ___

Formatting output

To display, a real value that represents money, use the 
placeholder %.2f. Value is rounded to 2 decimal places.

printf(“%.2f”, 4.9653);
4.97
printf(“%.1f”);
5.0

To display a value in a specified number of columns (say 
6), use the placeholder

%6d		for an integer
%6.1f	for real number to 1 decimal place

printf(“%6d”, 25);
    25

printf(“%6.1”, 5.123);
   5.1


Reading two or more data items with scanf

printf(“Enter hours and rate>”);
scanf(“%lf%lf”, &hours, &rate);

1st number stored in hours, second in rate. Should be at 
least one space between numbers. Don’t forget &’s!

char first, second;

printf(“Enter your two initials>”);
scanf(“%c%c”, &first, &second);

or

scanf(“ %c %c”, &first, &second);

The above form will ignore any whitespace (blanks or 
return characters) before either letter.

Enter your two initials>  E  K