#include <stdio.h>
#include <conio.h>
#include <stdlib.h>
main()
{
int choice,num1,num2,num3;
float THB,USD,JPY,CNY;
/*clrscr();*/
printf("===========Currency Converter===========\n");
      printf("1.THB<-->USD\n2.THB<-->JPY\n");
      printf("3.THB<-->CNY\n4.Exit\n");
      printf(" Please Select \n");
      printf("=========================\n");
      printf("Enter Number is:");
      scanf("%d",&choice);
switch(choice){
       case 1:printf("\n1.THB-->USD\n2.USD-->THB\n");
             printf(" Please Select \n");
             printf("=========================\n");
             printf("Enter Number is:");
             scanf("%d",&num1);
             break;
       case 2:printf("\n1.THB-->JPY\n2.JPY-->THB\n");
             printf(" Please Select \n");
             printf("=========================\n");
             printf("Enter Number is:");
             scanf("%d",&num2);
             break;
       case 3:printf("\n1.THB-->CNY\n2.CNY-->THB\n");
             printf(" Please Select \n");
             printf("=========================\n");
             printf("Enter Number is:");
             scanf("%d",&num3);
             break;
             case 4:exit(0);
             default:printf("Please Select 1-4\n");
             }      
switch(num1){
             case 1:printf("\nEnter THB =");
                  scanf("%f",&THB);
                  printf("=========================\n");
                  USD = THB*0.0314;
                  printf("USD =.2fUSD\n\n",USD);
                  break;
                  case 2:printf("\nEnter USD =");
                  scanf("%f",&USD);
                  printf("=========================\n");
                  THB = USD*31.85;
                  printf("THB = .2fTHB\n\n",THB);
                  break;                  
                  }
switch(num2){
             case 1:printf("\nEnter THB =");
             scanf("%f",&THB);
             printf("=========================\n");
             JPY = THB*3.12;
             printf("JPY =.2fJPY\n\n",JPY);
             break;
             case 2:printf("\nEnter JPY =");
             scanf("%f",&JPY);
             printf("=========================\n");
             THB = JPY*0.3124;
             printf("THB = .2fTHB\n\n",THB);
             break;
             }    
switch(num3){
             case 1:printf("\nEnter THB =");
             scanf("%f",&THB);
             printf("=========================\n");
             CNY = THB*0.1921;
             printf("CNY =.2fCNY\n\n",CNY);
             break;
             case 2:printf("\nEnter CNY =");
             scanf("%f",&CNY);
             printf("=========================\n");
             THB = CNY*5.20;
             printf("THB = .2fTHB\n\n",THB);
             break;
             }            
getch();
}


ผมก็ไม่ค่อยจะเป็นนะแต่เขียนส่งอาจารย์ ผมติดตรง switch(num2) case2 อะครับ มันชอบไปโผล่ ตอนจะจบทุกที ช่วยดูให้หน่อยนะครับ