Detailed explanation and examples of C language default usage

The default statement defines the default action in the switch statement when no case tags are matched. It is at the end of the switch statement and the syntax is "default: code to execute". The default tag is optional, and if not provided, nothing happens when the value of the switch expression does not match any case tags.

Detailed explanation of the usage of C language default

The default statement is used to define the default operation in the switch statement when no case tags are matched. It is usually at the end of a switch statement.

grammar

 <code>default: // 要执行的代码</code>

usage

1. Default operation for representing unmatched case tags: When the value of the switch expression does not match the value of any case tag, execute the code under the default tag.
2. Optional statement: The default statement is optional. If not provided, nothing happens when the value of the switch expression does not match any case tags.

Example

 <code class="c">#include <stdio.h> int main() { int choice; printf("Enter your choice (1-3): "); scanf("%d", &choice); switch (choice) { case 1: printf("You chose option 1.\n"); break; case 2: printf("You chose option 2.\n"); break; case 3: printf("You chose option 3.\n"); break; default: printf("Invalid choice.\n"); } return 0; }</stdio.h></code>

In the above example, when the user enters 1, 2, or 3, the program outputs the corresponding options. If the user enters an invalid option (i.e. not 1, 2, or 3), execute the default tag and output "Invalid choice".

Notice :

• The default tag does not require a break statement, because the switch statement will automatically exit after executing the code in the default tag.
• The default tag can be used with the case tag to handle multiple different options.

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