C-Language Summary (6)

1. Expression:

An arithmetic expression:

Monocular: +,-, + +,--。

Binocular: +,-,*,/,%.

An assignment expression:

Simple assignment: =

Compound assignment: +=,-=,*=,,/=%=,!=.

Relational Expressions:

>,>=,<,<=,!=.

Logical expression:

！ , &&,| |

Conditional expression:?

Comma-expression:,

Other operations: sizeof

2.++ operator

Self-increment, the decrement operator increases the value of the variable by 1 or minus 1.

Available in four different forms: i++ ++i I----I

The difference between i++ (i--) and ++i (-i):

The value of I is added (minus) 1 after performing the self-increment (minus) operation

However, the value of the expression is different: the value of i++ (i--) is the original value.

The value of ++i (-i) is the value after increment (minus) 1.

Attention:

The self-increment operator (+ +), the decrement operator (--) can be used only for variables, not constants or expressions.

+ + and--the combination of the direction is "from right to left."

3. Conditional expressions

Exp1? Exp2:exp3

Cases:

[If (x>0)

y=x+2; ===== [Y= (x>0) x+2:x*x]

Else

Y=x*x;]

4. Comma-expression

Expression 1, expression 2, Expression 3 ..... Expression n

The expression 1 is evaluated first, and then the expression 2 is evaluated .... And the value of the expression n as the value of the comma expression.

Int A,b,c;

(a=2), (b=3), (C=A+B);

The comma operator has the lowest priority and the left combination.

5. Other operations

Length operator: sizeof

Monocular operator, calculating the byte length of a variable or data type

Int A;

Sizeof (a)

The length of the shaping variable A, value 4 (bytes)

Sizeof (int)

Length of the shaper, Value 4 (bytes)

6. Definitions and references for a set of arrays

Definition of one-dimensional array

1. How to define:

Type an array group name [shaping constant expression];

Int A[10];

2. Description:

A, the naming and variable names of the array names are the same, followed by the identifier naming rules.

B, the constant expression after the array name is enclosed in [].

C, the constant expression represents the number of elements, that is, the array length.

Example: a[10] means that the array a contains 10 elements, respectively, a[0]-a[9]

3. The array must first be defined and then used. The C language specifies that the entire array can only be referenced one at a time.

4, initialization of array elements can be implemented in the following ways:

A, the array element is assigned an initial value when it is defined. such as: int a[10]={0,1,2,3,4,5,6,7,8,9};

B, you can assign values to a subset of elements. such as: int a[10]={0,1,2,3,4}, indicates that only the first five elements are assigned an initial value, the last five elements are automatically assigned to 0 values.

C, no initial value is assigned to the static array, and the system automatically assigns 0 values to all elements. That is: If you want to make the value of all elements in array a 0, you can define the array as follows: Static int a[5];

C-Language Summary (6)