c语言中case是什么意思

switch(表达式){
    case 整型数值1: 语句 1;[break;]
    case 整型数值2: 语句 2;[break;]
    ......
    case 整型数值n: 语句 n;[break;]
    default: 语句 n+1;[break;]
}

switch (1) {
    case 1.1:
        break;
}

int a;
scanf("%d", &a);
switch (a) {
    case a + 1:
        break;
}

#include <stdio.h>

int main () {

    
    char grade;
    scanf("%d", &grade);

    switch(grade) {
        case 'A' :
            printf("excellent!\n" );
            break;
        case 'B' :
        case 'C' :
            printf("Well done\n" );
            break;
        case 'D' :
            printf("You passed\n" );
            break;
        case 'F' :
            printf("Better try again\n" );
            break;
        default :
            printf("Invalid grade\n" );
    }

    printf("Your grade is  %d\n", grade );

    return 0;
}

#include <stdio.h>
int main() {

    printf("Please input your grade(1-100):");
    int grade;
    scanf("%d", &grade);

    switch (grade / 10) {
        case 10:
        case 9:
            printf("A\n");
            break;

        case 8:
        case 7:
            printf("B\n");
            break;

        case 6:
        case 5:
            printf("C\n");
            break;
        default:
            break;

    }
    return 0;
}