[codes=c]  #include <stdio.h>
    #include <ctype.h>
    #include <mem.h>
    #include <string.h>
    
    #define MAX 100
    #define TOAN 0
    #define LY   1
    #define HOA  2
    
    struct sinhvien {
      char mslop[5];
      char hoten[35];
      float diem[3];
    } danhsach[MAX];
    int n = 0;
    
    void nhapmoi()
    {
      char mslop[5], tmp[3];
      int i;
      float diem[3];
      do {
        printf("\nCho biet ma so lop : ");
        gets(mslop);
        if (strlen(mslop))
        {
          strcpy(danhsach[n].mslop, mslop);
          printf("\nCho biet ho ten : ");
          gets(danhsach[n].hoten);
          printf("\nCho biet diem so : ");
          for (i=0; i<3; i++)
          {
            scanf("%f", &diem[i]);
            danhsach[n].diem[i] = diem[i];
          }
          gets(tmp);
          n++;
        }
      } while (strlen(mslop));
    }
    
    void timkiem()
    {
      char mslop[5];
      int i = 0, found = 0;
      printf("\nCho biet ma so lop : ");
      gets(mslop);
      if (strlen(mslop))
        while (i<n)
          if (stricmp(danhsach[i].mslop, mslop) == 0)
          {
             printf("\nMa so lop : %s", danhsach[i].mslop);
             printf("\nHo va ten : %s", danhsach[i].hoten);
             printf("\nDiem Toan : %f", danhsach[i].diem[TOAN]);
             printf("\nDiem Ly   : %f", danhsach[i].diem[LY]);
             printf("\nDiem Hoa  : %f", danhsach[i].diem[HOA]);
             found = 1;
             break;
          }
          else
            i++;
      if (!found)
        printf("\nKhong tim thay!!!");
    }
    
    void xoa()
    {
      char mslop[5], traloi;
      int i = 0, j;
      printf("\nCho biet ma so lop : ");
      gets(mslop);
      if (strlen(mslop))
        while (i<n)
          if (stricmp(danhsach[i].mslop, mslop) == 0)
          {
             printf("\nMa so lop : %s", danhsach[i].mslop);
             printf("\nHo va ten : %s", danhsach[i].hoten);
             printf("\nDiem Toan : %f", danhsach[i].diem[TOAN]);
             printf("\nDiem Ly   : %f", danhsach[i].diem[LY]);
             printf("\nDiem Hoa  : %f", danhsach[i].diem[HOA]);
             printf("\nCo muon xoa khong (C/K)? ");
             do {
               traloi = toupper(getch());
             } while (traloi != 'C' && traloi != 'K');
             putc(traloi, stdout);
             if (traloi == 'C')
             {
               n–;
               memcpy(&danhsach[i], &danhsach[i+1], sizeof(struct sinhvien) * (n-i));
               break;
             }
          }
          else
            i++;
    }
    
    void menu()
    {
      printf("\n");
      printf("\n 1. Them     ");
      printf("\n 2. Xoa      ");
      printf("\n 3. Tim kiem ");
      printf("\n 0. Thoat    ");
      printf("\n");
      printf("\nChon lua ? ");
    }
    
    void main()
    {
      char traloi;
      do {
        menu();
        do {
          traloi = getch();
        } while (traloi < '0' || traloi > '3');
        putc(traloi, stdout);
        switch (traloi)
        {
           case '1' : nhapmoi();
                      break;
           case '2' : xoa();
                      break;
           case '3' : timkiem();
                      break;
        }
      } while (traloi != '0');
    }  [/codes]