c语言dowhile语句的用法(c语言使用dowhile语句输出奇数和偶数和)

1. Introduction to do-while loop

The do-while loop is a control flow statement in the C programming language that executes a block of code repeatedly until a specified condition becomes false. It is similar to the while loop, but with one key difference - the block of code is executed at least once, regardless of whether the condition is true or false.

2. Syntax and usage

The syntax of the do-while loop in C is as follows:

do {
    // code block to be executed
} while (condition);

The code block will be executed first, and then the condition is evaluated. If the condition is true, the code block will be executed again. This process will continue until the condition becomes false. Therefore, the block of code is guaranteed to execute at least once.

The condition itself is a boolean expression. It can be any valid C expression that evaluates to either true or false. If the condition evaluates to true, the loop continues; if it evaluates to false, the loop terminates, and the program moves on to the next line of code after the loop.

3. Practical examples

Now, let's take a look at some practical examples of using the do-while loop in C.

Example 1: Sum of numbers

#include<stdio.h>
int main() {
    int sum = 0;
    int num;
    
    do {
        printf("Enter a number (enter 0 to exit): ");
        scanf("%d", &num);
        sum += num;
    } while (num != 0);
    
    printf("The sum of the numbers is: %d\n", sum);
    return 0;
}

In this example, the user is prompted to enter numbers one by one. The program calculates the sum of these numbers and continues to prompt for input until the user enters 0, at which point the loop terminates, and the sum is displayed.

Example 2: Password validation

#include<stdio.h>
#include<stdbool.h>
int main() {
    char password[10];
    bool valid = false;
    
    do {
        printf("Enter password: ");
        scanf("%s", password);
        
        // check if password is valid
        if (strcmp(password, "password123") == 0) {
            valid = true;
        }
        
    } while (!valid);
    
    printf("Access granted!\n");
    return 0;
}

In this example, the user is prompted to enter a password. The program checks if the entered password is valid (in this case, it checks if the password is "password123"). If the password is invalid, the user is prompted to enter a password again until a valid password is entered. Once a valid password is entered, the loop terminates, and the program displays "Access granted!"

In conclusion, the do-while loop in C is a useful construct when we want a block of code to execute at least once, regardless of the condition. It is particularly useful in situations where we need to validate user input or perform iterative calculations. By understanding the syntax and practicing with examples, you can effectively use the do-while loop in your C programs to achieve desired outcomes.