1. Comments
Any string of symbols placed between the delimiters /* and */.
Can span multiple lines
Can’t be nested! Be careful.
/* /* /* Hi */ is an example of a comment.
Keywords
Reserved words that cannot be used as variable names
OK within comments . . .
Examples: break, if, else, do, for, while, int, void
Exhaustive list in book

2. Identifiers Constants
A “token” (“word”) composed of a sequence of letters, digits, and underscore (“_”) character. (NO spaces.)
Used to give names to variables, functions, etc.
Identifiers such as “printf” normally would not be redefined; be careful
Only the first 31 characters matter
Constants
Will discuss more in near future.
0, 77, examples.
Strings: double quotes. “Hello”
Characters: single quotes. ‘a’ , ‘z’
Have types implicitly associated with them…
too large for most machines…

3. Operators and “Punctuators”
These are special characters with particular meanings, potentially depending on context
+ - * / are the usual arithmetic operators, and can be applied to integer types as well as floating-number types
% is “mod operator”: a % b is equal to the remainder when a is divided by b, and returns a value in the range 0…(b – 1). We won’t worry about what happens when either a or b is non-positive.
% character has different meaning in printf( “%d”, a );
Punctuators include parentheses, braces, semicolons…
Some special operators provided by C
++, --, +=, -=. Increment/decrement, assignment…
x += 2; equivalent to x = x + 2;
a--; equivalent to a -= 1;
Left hand side of any assignment must be “lvalue”; x + 2 is not a valid lvalue

4. Precedence of Operators
You may have learned about this in the third grade:
1 + 2 * 3 has the value of 1 + (2 * 3)
If we want the addition to be performed first, must parenthesize: (1 + 2) * 3.
We say that * has a higher precedence than +.
See K&R page 53.
Associativity of Operators
Question number two: What about operators at the same precedence level? For instance, * and / ?
Is 12 / 6 * 2 equal to (12 / 6) * 2, or 12 / (6 * 2) ?
It’s the first: these operators are left associative (as are most)
Moral of story: I say parenthesize when in doubt.

5. ++ , the tricky guy Two variants: before a variable and after.
int a = 10;
printf( “%d”, a++ );
int a = 10;
printf( “%d”, ++a );
I prefer personally not to mix in ++ or – as part of a more complicated expression
Another complication:
int a = 10;
printf( “%d %d”, a++, a++ );
This complication not limited to the ++, -- operators, but occur with any operator with side effects