C language selection structure, the characteristics of the three basic structures of C language

The first if(!) a) means that if a is equal to zero, take x -- the second and third means that if b and c are not 0, it is executed.

The fourth is to perform in other cases.

The program executes two of them, the first and the fourth, that is, x-and then x=4, so it's 4. It's a fascinating trap.

Seriously, I was dizzy the first time I saw it, and it was redundant and ineffective when actually programming.

No, there is no ; Indicates that the statement has ended, and the nesting has ended accordingly.

if(b);It is followed by a semicolon to prove that the demolition is complete.

So only the last two sentences are useful.

In C, there are three basic program structures: sequential structures, selection structures, and loop structures. 1. Sequential structure.

The sequential structure indicates that the actions in the program are performed in the order in which they appear'The characteristic of this structure is that the program starts from the entry point A and performs all operations sequentially until the exit point B, so it is called a sequential structure.

2. Select the structure.

Selecting a structure indicates that a program's processing steps have branched, and it needs to select one of the branches to execute according to a specific condition. There are three types of selection structures: single choice, double choice and multiple choice.

3. Circulating structure.

A loop structure means that a program performs one or more actions over and over again until a condition is false (or true) before terminating the loop. The main thing in the loop structure is: when is the loop executed?

What operations need to be performed in a loop? There are two basic forms of the loop structure: the current cycle and the until the cycle, and when the cycle is executed depends on the conditions.

The C language selection structure, also known as the branch structure, is to let the program "turn around" and execute selectively**; In other words, it's possible to skip the useless and only execute the useful.

The C sequential structure is to have the program execute each C language in sequence from beginning to end, without repeating any ** and not skipping any**. The C loop structure is to let the program "kill the gun" and repeat the same paragraph over and over again.

There are three programming constructs commonly used in C (as are other programming languages), and they are:

Sequential structure: Execute from front to back, without any "beating around the bush", without skipping any statement, all statements will be executed.

Select a structure: Also known as a branch structure. ** will be divided into multiple parts, and the program will determine which part to execute based on specific conditions (the result of the evaluation of an expression).

Loop structure: The program will re-execute the same paragraph until the condition is no longer met, or it encounters a forced pop-out statement (break keyword).

First, identify the problem to be solved; secondly, analyze the problem and choose the algorithm you want to use, or think of an algorithm yourself; Draw a flowchart to clarify the logical relationship and timing relationship in the process of solving the problem; Then it is written on the machine**; After that, it's debugging, and it's basically ready to be executed. Specifically, in terms of computer writing, you first need to open the C++ development environment, and then create a new project; Then create a new file (if it is, you can continue to write, if it is vs20**, you need to select Move file into project in the file menu); Write ** in the file, and then you can compile and run. In terms of the specific format of **, you should first refer to the header file include, and then add a line using namespace std after all header files are introduced; You can write the function later.

The basic structure is as follows:

1. A C program is composed of one or more functions, a C function is composed of several C statements, and a C statement is composed of a number of basic words. Refers to air strikes.

2. The C function is the smallest unit to complete an overall function, and it is a relatively independent module. A simple C program may have only one main function, while a complex C program may contain a main function and any number of other functions, all of which have three parts in structure: the function name, the formal arguments, and the function body.