Why are you writing this line largest = nvalue; ?
And your if-else if commands are totally wrong.
Try this code:
#include <stdio.h>
int main(){
    int largest = 0;
    int no1, no2, no3;
    printf("Number1: ");
    scanf("%d", &no1);
    printf("Number2: ");
    scanf("%d", &no2);
    printf("Number3: ");
    scanf("%d", &no3);
    if ((no1 > no2) && (no1>no3)){
        largest=no1; 
    }
    else if ((no2 > no1) && (no2>no3)) {
        largest=no2; 
    }
    else {
        largest=no3; 
    }
    printf("The largest number is:%d", largest);
    return 0;
}
4
solved C Program not working