So i am trying to make an switch statement that checks if the user has not already entered that switch statement before and I am trying to do this with an if statement inside the switch, but it always ignores the if statement and always just completes the case which is inside it, disregarding the other arguments, but what is also interesting is that it changes a to bijis, but doesnt do the actual condition check:

char bijis = '*';
char izv;
printf("\nChoose the next station ");  
scanf("%d",&izv);  

switch(izv)  {  
if (a != bijis) {
    case 'a': case 'A':  
    a = bijis;
    jaut_a();
    break; 
} 
    if (b != bijis) {
        case 'b': case 'B':
        b = bijis;       
        jaut_b();  
        break;  
}
     if (c != bijis) {
        case 'c': case 'C':
        c = bijis;       
        jaut_c();  
        break;  
}
     if (d != bijis) {
        case 'd': case 'D':
        d = bijis;       
        jaut_d();  
        break;  
}
     if (e != bijis) {
        case 'e': case 'E':
        e = bijis;       
        jaut_e();  
        break;  
}
     if (k1 != bijis) {
        case '1':
        k1 = bijis;       
        jaut_k1();  
        break;  
}
     if (k2 != bijis) {
        case '2':
        k2 = bijis;       
        jaut_k2();  
        break;  
}
     if (k3 != bijis) {
        case '3':
        k3 = bijis;       
        jaut_k3();  
        break;  
}
     if (k4 != bijis) {
        case '4': 
        k4 = bijis;       
        jaut_k4();  
        break;  
}
     if (k5 != bijis) {
        case '5': 
        k5 = bijis;       
        jaut_k5();  
        break;  
}
     if (k6 != bijis) {
        case '6': 
        k6 = bijis;       
        jaut_k6();  
        break;  
}
     if (k7 != bijis) {
        case '7':
        k7 = bijis;       
        jaut_k7();  
        break;  
}
     if (k8 != bijis) {
        case '8' :
        k8 = bijis;       
        jaut_k8();  
        break;  
}
     if (k9 != bijis) {
        case '9' :
        k9 = bijis;       
        jaut_k9();  
        break;  
}
          default:  
          clearscr();
          printf("Kļūdaina ievade, šajā lauciņā jau esi bijis! Ieraksti jebkuru burtu vai skaitli,kas rādīts tabulā.\n (Zvaigznītes parāda vietas kur jau esi bijis.");
          sleep(3.5);
          karte_plans();
          break;  
    } ;