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Output function: printf () -% d,% c,% x,% u,% s,

Putchar () function: output

Input function: scanf function-input

Gets the data of the specified type according to the specified format match

Int a; / / you can define a variable (with memory space) or declare it (automatically promoted to definition, with memory space)

Scanf ("% d", & a); / / & take the address of the variable an and get the memory space of a

Scanf input: getting characters in

Getchar function: getting characters

Operator-arithmetic operator

+, -, *, /: multiply, divide and take the remainder, then add and subtract

After the division operation, the result is assigned to the integer variable, taking the integer part, int c = 20prime 40.

Except 0, error operation, not allowed, printf ("% d\ n", 20max 20)

Take the balance to 0, error operation, not allowed, printf ("% d\ n", 1234ap0)

The remainder of the decimal is not allowed.

If you take the remainder of a negative number, the result is the absolute value of the remainder.

Self-increasing and self-subtracting operator

Prefix self-increment (increment operator): (+ +), self-subtraction (decrement operator): (- -): first increase, decrease, and then take a value

Assignment operator: =

"=", in the computer, can only complete the assignment operation, must be the right side of the assignment to the left, also known as one-way assignment and so on.

A + = 10; / / equivalent to a = axi10

A-= 30; / / equivalent to a = a muri 30

A% = 5; / / is equivalent to a = a% 5; comparison operator

True: 1 (non-0), false: 0

! = unequal,

Greater than or equal to

Logical operators: 0 is false, non-0 is true, (non-zero 1, 27,-9)

Logic is not:!

Non-true is false, non-false is true

Logic and (& &): the same truth is true and the rest is false.

Logic or (| |): true is true, and false is false.

Operator precedence: [], (), +, /,--

Suffix is higher than prefix (strong turn)! (logical non) sizeof > arithmetic operator (first multiply, divide and subtract the remainder) > comparison operator > logical operator > trinomial operator (conditional operation) > assignment operator > comma operator

Comma operator:

Int x, y, z

Int a = (x = 1, y = 2, z = 3) / / comma operation expression, the result is: a = 3

The result of the comma operator expression operation, which displays the result of the latter subexpression

Ternary operator

Syntax: expression 1? Expression 2: expression 3

Expression 1: must be a judgment expression

The result is true: the whole trinocular operation returns expression 2, the result is false, the whole trinocular operation returns expression 3

Type conversion: implicit type conversion, forced type conversion

Editor is automatically completed, small type to large type, the same type size

Generated by assignment

Int r = 5

Float s = 3.14 * r * r

3.14. The default type is double. R is int. During the operation, it is converted to double. When the operation is finished, it is converted to float when assigned to s.

There is no problem with changing a small type to a large type. If a large type is converted to a small type, the precision may be lost.

Force conversion in a class

Syntax: strong transformation quantity-(target type) variable, strong turn expression-(target type) expression

If branch statement

If (judgment expression) {

Can it be executed if the discriminant expression is true?

}

Else

{

Judge whether the expression is false and execute the code

}

Multi-branch logic

If (judgment expression 1)

{

Judge that expression 1 is true and execute the code

}

Else if (judgment expression 2)

{

Judge whether expression 1 is false, judge expression 2 is true, and execute the code

}

Else if (judgment expression 3)

{

Judge whether expression 1 is false, judge expression 2 is false, judge expression 3 is true, execute code

}

Switch branch statement

Switch (discriminant expression)

{

Case 1:

Execute statement

Break;// indicates the end of execution of a branch statement and jumps out of the switch

Case 2:

Execute statement

Break

.

Case n:

Execute statement

Break

Default

Break

}

Accurate matching, clear mechanism, higher execution effect than if statement

Case penetration

A case branch, if there is no break, each time the case code is executed, it will continue to go down and execute the next case branch code, which is called case traversal.

In most cases, a case branch should correspond to a break that takes advantage of case tradition

While loop statement

Syntax: while (judgment expression) / / if true, execute the loop body, if false, jump out of the loop

{

Cyclic body

}

Do... while Loop statement

Syntax: do {

Cyclic body

} while (judgment expression)

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