C Language Program Structure branch structure if switch

One, the structure of the program: Sequential structure: The program runs in accordance with the normal process of running (the program inside the implementation of linear structure: stack, Team

column, linked list, array of personal feelings)

Branching structure: Conditional statements if switch

Loop structure: While do and for

Two, if statement

1, Category 1) The first form of:

Composition: if (expression) {

statement block;

}

2) Form of If....else

Usage: If the value of an expression is true (1) the statement block 1 is executed

If the value of the expression is False (0) to execute the statement block 2

Format: if (expression)

{

If the value of an expression is true (1), this line of code blocks

Statement Block 1;

}

Else

{

If the expression value is False (0), the contents of the else brace are executed

Statement Block 2;

}

3) nested use of If...else

if (condition 1) {

Statement Block 1;

if (condition 2) {//condition 1 is True

}

}else{

}

4) If ... else if...else

if (condition 1) {

Statement Block 1

}else if (condition 2) {

}else if (condition 3) {

}

else{

}

2, note: After the IF statement whether or not the following is an empty statement or a sentence plus {} (to prevent errors)

1) if (); A ";" can be written directly after the IF statement. （“;” Empty statement), indicating that nothing is done

2) When the IF statement is true, you can omit the parentheses when you simply execute a sentence

3) if (1) or if (-1) are permanent, if (0) Permanent

4) The problem of the scope disorder

if (a>0) int num=-1; Num variable will error, can be added {}

printf ("%d\n", num);

5) If the problem of omitting curly braces

Method: From bottom to top find else according to else find can match if

6) return keyword within the function, the end of the program;

7) A leap year must be interpreted in years that are divisible by 4 and not divisible by 100, or that the year is divisible by 400;

Three, switch statement

1) switch statement a branch statement

Format: switch (expression) {

case constant Expression 1: statement 1;

Case constant Expression 2: statement 2;

Case constant Expression 3: statement 3;

case constant Expression N: statement n;

Default

are not satisfied with the execution of the statement;

}

2) Attention Issues

1>case: In order to prevent penetration, we use break;break, we can end the Swith statement prematurely

If the case ends without a break in each condition, the program continues execution until the break ends;

The return value type of the 2>switch (expression) expression cannot be float\double, can be integer, and character type

The case is also a constant expression;

3> If you define a variable, you need to enclose it in curly braces.

int a=3;

Switch (a+3) {

default:printf ("error\n");

Case 6:

printf ("xxx");

int num =-1;

Break

}

C Language Program Structure branch structure if switch