Which of the following is not a valid variable name? 2 myint 2. return 3. myinteger 4. total3

Correct answer is option (2) that is "return".

Explanation:

In any programming language, a variable name can be made up of letters (lower and upper case) and digits. we can also use "_" underscore character for declaring the variables but we cannot use any special character like “$”.We cannot use digits in the beginning of variables name. And we also cannot use reserved keywords of the language like "new","return","while" etc. There should not be space between the variable names. Options 1, 3 and 4 are not violating any of these properties. But in option (2), "return" is a reserved keyword. That is why it is not a valid variable name.

Some example of valid variables name:

foo

BAZ

Bar

_foo42

foo_bar

Some example of invalid variables name:

$foo    ($ not allowed)

while   ( keywords )

2foo    (started with digit)

my foo  (spaces )

The different variable in C is 21213316700.

Explanation:

Given value:

Total value  = letters + underscore value

Total value  = 52 + 1

Total value =53

choice for first character = 53 letters +10 digits

first character = 63

choice for remaining characters

So,

Variable number With one 1 character = 53

Variable number With 2 character  = 53 × 63

Variable number With 3 character = 53 × 63²

Variable number With 4 character  = 53 × 63³

.

.

.

Variable number With 7 character  =

Total difference variable = 53 + 53 × 63+ 53 × 63²+ 53 × 63³+....+

Total difference variable = 53(1 + 63 + 63²+ 63³+ .... + )

Formula:

Total difference variable