c knowledge solves, c operators solve

Regular expressions:

d+$**：

if(, "^\d+$"))

It's numbers. else is not a number.

Actually, everything that is entered by humans in the textbox is string type data.

In other words, what you read in ** is actually a string type of data.

Summary:

Relational operations, also known as comparative operations, require at least two or more variables to participate in the operation.

Logical operations, mainly non, and, or.

Body

The following table shows all the relational operators supported by C. Hypothetical variablesahas a value of 10, variablebA value of 20 is then:

Multiple relational operations are connected.

Logical operatorsThe following table shows all the logical operators supported by C. Hypothetical variablesais a boolean true, variablebIf the Boolean value is false, then:

With &, |With &, |The difference.

Two &&& or ||Also known as the short-circuit operator, as long as the first operator is determined to be false or true, the operation after the code leakage will not be done.

A simple example.

This is where prefix and suffix operators come into play.

a=10 So when the first a++ runs, the value of a is still 10, and when the operation is over, a=11 (because it is a suffix, so 1 is added after the operation).

The second ++a, the value of a is already 11, and then add 1 to 12 (because it is a prefix, it is necessary to add 1 before calculation).

The third, a--, is the same, first calculate and then subtract, so it is also 12, and after the operation is over, it is 11 The fourth, first subtract 1, and then run, so it is 10

The end result is 10,12,12,10

a++ is assigned after the value is self-priced, and ++a is assigned after the self-addition.

Books should be familiar and understood.

a++, take a first, then increment.

a, increment first, and then take a

A--, take A first, then decrement.

a, decrement first, then a

:)a++: The value of a is 10, and the value of a becomes 11

a: If the value of a is 11+1, it is 12

Analogy...

a++ is assigned first and then ++, so a++ is 10, and then a becomes 11

A is a ++ and then assigned, so ++a is 12, and then a becomes 12

In the same way, a-- a is the same as above.

The value of the a++ expression is 10, but the value of a is 11: ++ is the last, take the value first, and then calculate the value of the ++a expression is the value of a plus 1, that is, 12, the value of a also becomes 12, :+ is in the front, calculate first, and then take the value.

a-- the value of the expression is 12, but the value of a is 11:--later, the value is taken first, and then the value of the --a expression is the value of a minus 1, i.e. 10, and the value of a becomes 10, :- in front, it is calculated first, and then the value is taken.

d. A logical data structure can have a variety of storage structures, and various storage structures affect the efficiency of data processing.

C In-Depth is a comprehensive and systematic introduction to the C programming language, covering all areas of the C language. Combined with the author's years of development and teaching experience, the C programming language is introduced and analyzed from the most basic theoretical concepts to practical examples, from the simplest C programming knowledge to the most complex technical fields.