int testtyp(typset, int);

void interpret(){
    order ir;
    int pc;
    int ps;
    int run    = 1,
        fin    = 2,
	caschk = 3,
	divchk = 4,
	inxchk = 5,
	stkchk = 6,
	linchk = 7,
	lngchk = 8,
	redchk = 9;
    int t; // top of stack index
    int b; // base index
    int lncnt, ocnt, blkcnt, chrcnt; // counters
    int h1, h2, h3, h4;
    int fld[5]; // field width
    int display[101]; // lmax +1
    types s[100001];// stacksize +1
    int it =0;
    long fpos;
    char newch;
    /*
        blockmarks:
	    s[b+0] = fct result
	    s[b+1] = return adr
	    s[b+2] = static link
	    s[b+3] = dynamic link
	    s[b+4] = table index
    */
    s[1].i = 0;
    s[2].i = 0;
    s[3].i = -1;
    s[4].i = btab[1].last;
    b = 0;
    display[1] = 0;
    t = btab[2].vsize - 1;
    pc = tab[s[4].i].adr;
    ps = run;
    lncnt = 0;
    ocnt = 0;
    chrcnt = 0;
    fld[1] = intfld;
    fld[2] = relfld;
    fld[3] = bolfld;
    fld[4] = chrfld;
    do{
        ir = code[pc];
		//printf("        pc = %d ir.f = %d ir.y = %d ir.x = %d instrution name = %s\n",pc, ir.f, ir.y, ir.x, mnemonics[ir.f]);
		pc = pc + 1;
		ocnt = ocnt + 1;
		switch(ir.f){
			case 0:// load address
				t = t+1;
				if(t > stacksize) ps = stkchk;
				else s[t].i = display[ir.x] + ir.y;
				break;
			case 1:// load value
				t = t+1;
				if (t > stacksize) ps = stkchk;
				else s[t] = s[display[ir.x]+ir.y];
				break;
			case 2:// load indirect
				t = t+1;
				if (t > stacksize) ps = stkchk;
				else s[t] = s[s[display[ir.x]+ir.y].i];
				break;
			case 3:// update display
				h1 = ir.y;
				h2 = ir.x;
				h3 = b;
				do{
					display[h1] = h3;
					h1 = h1 - 1;
					h3 = s[h3+2].i;
				}while(h1 != h2);
				break;
			case 8:
				switch(ir.y){
					case 0: s[t].i = abs(s[t].i); break;
					case 1: s[t].r = abs(s[t].r); break;
					case 2: s[t].i = s[t].i * s[t].i; break;
					case 3: s[t].r = s[t].r * s[t].r; break;
					case 4: s[t].b = s[t].i%2; break;
					case 5:
							s[t].c = s[t].i;
							if(s[t].i < 0 || s[t].i > inxmax) ps = inxchk;
							break;
					case 6: s[t].i = s[t].c; break;
					case 7: s[t].c = s[t].c + 1; break;
					case 8: s[t].c = s[t].c - 1; break;
					case 9: s[t].i = round(s[t].r); break;
				   case 10: s[t].i = trunc(s[t].r); break;
				   case 11: s[t].r = sin(s[t].r); break;
				   case 12: s[t].r = cos(s[t].r); break;
				   case 13: s[t].r = exp(s[t].r); break;
				   case 14: s[t].r = log(s[t].r); break;
				   case 15: s[t].r = sqrt(s[t].r); break;
				   case 16: s[t].r = atan(s[t].r); break;
				   case 17: 
							t = t+1;
							if(t > stacksize) ps = stkchk;
							else{
								if(line[cc+1] == EOF)s[t].b = 1;
							else s[t].b = 0;
							}
							break;
				   case 18: 
							t = t + 1;
							if(t > stacksize) ps = stkchk;
							else{
							if(cc==ll-1)s[t].b = 1;
							else s[t].b = 0;
							}
							break;
			}
			break;
			case 9: s[t].i = s[t].i + ir.y; break; // offset
		   case 10: pc = ir.y; break; // jump
		   case 11: //conditional jump
	            if(!s[t].b) pc = ir.y;
				t = t-1;
				break;
			case 12: //switch
					h1 = s[t].i;
					t = t - 1;
					h2 = ir.y;
					h3 = 0;
					do{
						if(code[h2].f != 13){
						h3 = 1;
						ps = caschk;
					}
						else if(code[h2].y == h1) {
						h3 = 1;
						pc = code[h2+1].y;
					}
					else h2 = h2 + 2;
					}while(h3 == 0);
					break;
		   case 14: //for1up
					h1 = s[t-1].i;
					if (h1 <= s[t].i) s[s[t-2].i].i = h1;
					else {
						t = t-3;
					pc = ir.y;
					}
					break;
		   case 15: //for2up
					h2 = s[t-2].i;
					h1 = s[h2].i +1;
					if(h1 <= s[t].i) {
						s[h2].i = h1;
					pc = ir.y;
					}
					else t = t -3;
					break;
		   case 16: // for1down
					h1 = s[t-1].i;
					if (h1 >= s[t].i) s[s[t-2].i].i = h1;
					else {
					pc = ir.y;
					t = t-1;
					}
					break;
		   case 17: // for2down
					h2 = s[t-2].i;
					h1 = s[h2].i -1;
					if(h1 >= s[t].i){
						s[h2].i = h1;
					pc = ir.y;
					}
					else t = t-3;
					break;
		   case 18: // mark stack
					h1 = btab[tab[ir.y].ref].vsize;
					if(t+h1 > stacksize) ps = stkchk;
					else {
						t = t+5;
					s[t-1].i = h1-1;
					s[t].i = ir.y;
					}
					break;
		   case 19: //call
					h1 = t - ir.y;// h1 points to the top base
					h2 = s[h1+4].i;
					h3 = tab[h2].lev;
					display[h3+1] = h1;
					h4 = s[h1+3].i + h1;
					s[h1+1].i = pc;
					s[h1+2].i = display[h3];
					s[h1+3].i = b;
					for (h3 = t+1; h3 <= h4; h3++) s[h3].i = 0;
					b = h1;
					t = h4;
					pc = tab[h2].adr;
					break;
		   case 20: //index
					h1 = ir.y; // h1 points to atab
					h2 = atab[h1].low;
					h3 = s[t].i;
					if (h3 < h2) ps = inxchk;
					else if(h3 > atab[h1].high) ps = inxchk;
					else {
						t = t -1;
					s[t].i = s[t].i + (h3-h2);
					}
					break;
		   case 21: //index
					h1 = ir.y;
					h2 = atab[h1].low;
					h3 = s[t].i;
					if(h3 < h2) ps = inxchk;
					else {
						t = t-1;
					s[t].i = s[t].i + (h3-h2)*atab[h1].elsize;
					}
					break;
		   case 22: // load block
					h1 = s[t].i;
					t = t-1;
					h2 = ir.y + t;
					if(h2 > stacksize) ps = stkchk;
					else while(t < h2){
						t = t+1;
					s[t] = s[h1];
					h1 = h1+1;
					}
					break;
			case 23: h1 = s[t-1].i;
					h2 = s[t].i;
					h3 = h1 + ir.y;
					while ( h1 < h3 ){
						s[h1] = s[h2];
						h1 = h1+1;
						h2 = h2+1;
					}//end while
					t = t-2;
					break;
			case 24: t = t+1;
					if ( t > stacksize ) ps = stkchk;
					else s[t].i = ir.y;
					break;
			case 25: t  = t+1;
					if ( t > stacksize ) ps = stkchk;
					else s[t].r  = rconst[ir.y];
					break;
			case 26: h1 = t - ir.y;
					s[h1].r = s[h1].i;
					break;
			case 27: //read
					 if(ch == EOF) ps = redchk;
					 else {
						 switch (ir.y){
							 case 1: // ints
							 insymbol();
							 if(sy != intcon){
								 printf("Input error integer expected %s recieved\n", symbolname[sy]);
								 exit(1);
							 }
							 s[s[t].i].i = inum;
							 break;
							 case 2: // reals
							 insymbol();
							 if(sy != realcon){
								 printf("Input error real expected %s recieved\n", symbolname[sy]);
								 exit(1);
							 }
							 s[s[t].i].r = rnum;
							 break;
						case 4: // chars 
								nextch();
								s[s[t].i].c = ch; 
								break;
						 }
					 }
					 t = t-1;
					 break;	
			case 28: h1 = s[t].i;
					h2 = ir.y;
					t = t-1;
					chrcnt = chrcnt + h1;
					if ( chrcnt > lineleng ) ps = lngchk;
					do{
						printf("%c", stab[h2]);
						h1 = h1 - 1;
						h2 = h2 + 1;
					}while(h1 > 0);
					break;
			case 29: chrcnt = chrcnt + fld[ir.y];
					if ( chrcnt > lineleng ) ps = lngchk;
					else{
						switch (ir.y){
							case 1: printf("%*d", fld[1], s[t].i); break;
							case 2: printf("%*f", fld[2], s[t].r); break;
							case 3: printf("%*d", fld[3], s[t].b); break;
							case 4: printf("%c", s[t].c); break;
						}//end switch		
					}//end else
					t = t-1;
					break;
			case 30: chrcnt = chrcnt + s[t].i;
					if ( chrcnt > lineleng )
						ps = lngchk;
					else{
						switch (ir.y){
							case 1: printf("%*d", s[t].i, s[t-1].i); break;
							case 2: printf("%*f", s[t].i, s[t-1].r); break;
							case 3: printf("%*d", s[t].i, s[t-1].b); break;
							case 4: printf("%*c", s[t].i, s[t-1].c); break;
						}//end switch
					}//end else
					t = t-2;
					break;
			case 31: ps = fin; break;
			case 32: t = b-1;
					pc = s[b+1].i;
					b = s[b+3].i;
					break;
			case 33: t = b;
					pc = s[b+1].i; 
					b = s[b+3].i;
					break;
			case 34: s[t] = s[s[t].i];	break;
			case 35: s[t].b = !s[t].b;	break;
			case 36: switch (ir.y){
						case 1: s[t].i = -s[t].i; break;
						case 2: s[t].r = -s[t].r; break;	
					}
					break;
			case 37: chrcnt = chrcnt + s[t-1].i;
					if ( chrcnt > lineleng ) ps = lngchk;
					else printf("%*.*f", s[t-1].i, s[t].i, s[t-2].r);
					t = t-3;
					break;
			case 38: s[s[t-1].i] = s[t];
					t = t-2;
					break;
			case 39: t = t-1;
					s[t].b = (s[t].r == s[t+1].r);
					break;
			case 40: t = t-1;
					s[t].b = (s[t].r != s[t+1].r);
					break;
			case 41: t = t-1;
					s[t].b = (s[t].r < s[t+1].r);
					break;
			case 42: t = t-1;
					s[t].b = (s[t].r <= s[t+1].r);
					break;
			case 43: t = t-1;
					s[t].b = (s[t].r > s[t+1].r);
					break;
			case 44: t = t-1;
					s[t].b = (s[t].r >= s[t+1].r);
					break;
			case 45: t = t-1;
					s[t].b = (s[t].i == s[t+1].i);
					break;
			case 46: t = t-1;
					s[t].b = (s[t].i != s[t+1].i);
					break;
			case 47: t = t-1;
					s[t].b = (s[t].i < s[t+1].i);
					break;
			case 48: t = t-1;
					s[t].b = (s[t].i <= s[t+1].i);
					break;
			case 49: t = t-1;
					s[t].b = (s[t].i > s[t+1].i);
					break;
			case 50: t = t-1;
					s[t].b = (s[t].i >= s[t+1].i);
					break;
			case 51: t = t-1;
					s[t].b = (s[t].b || s[t+1].b);
					break;
			case 52: t = t-1;
					s[t].i = s[t].i + s[t+1].i;
					break;
			case 53: t = t-1;
					s[t].i = s[t].i - s[t+1].i;
					break;
			case 54: t = t-1;
					s[t].r = s[t].r + s[t+1].r;
					break;
			case 55: t = t-1;
					s[t].r = s[t].r - s[t+1].r;
					break;
			case 56: t = t-1;
					s[t].b = (s[t].b && s[t+1].b);
					break;
			case 57: t = t-1;
					s[t].i = s[t].i * s[t+1].i;
					break;
			case 58: t = t-1;
					if ( s[t+1].i == 0 ) ps =  divchk;
					s[t].i = s[t].i / s[t+1].i;
					break;
			case 59: t = t-1;
					if ( s[t+1].i == 0 ) ps = divchk;
					s[t].i = s[t].i % s[t+1].i;
					break;
			case 60: t = t-1;
					s[t].r = s[t].r*s[t+1].r;
					break;
			case 61: t = t-1;
					s[t].r = s[t].r/s[t+1].r;
					break;
			case 62: 
					if(line[cc+1] == EOF)ps = redchk;  
					else nextch();
					break;
			case 63: printf("\n");
					lncnt = lncnt + 1;
					chrcnt = 0;
					if ( lncnt > linelimit ) ps = linchk;
					break;
		}//end switch
    }while(ps == run);//end do while loop
	if ( ps != fin ) {
		printf("\n");
		printf("halt at %5d because of", pc);
		printf("\n");
		switch (ps) {
			case 3: printf("undefined case\n"); break;
			case 4: printf("division by 0\n"); break;
			case 5: printf("invalid index\n"); break;
			case 6: printf("storage overflow\n"); break;
			case 7: printf("too much output\n"); break;
			case 8: printf("line too long\n"); break;
			case 9: printf("reading past the end of file\n"); break;
		}
		h1 = b;
		blkcnt = 10;
		do{
			printf("\n");
			blkcnt = blkcnt - 1;
			if ( blkcnt == 0 ) h1 = 0;
			h2 = s[h1+4].i;
			if ( h1 != 0 ) printf(" %s called at %5d", tab[h2].name, s[h1+4].i);
			h2 = btab[tab[h2].ref].last;
			while ( h2 != 0 ){
				if ( tab[h2].obj == variable )
					if ( testtyp(stantyps, tab[h2].typ) ){
						printf("     %s = ", tab[h2].name);
						if ( tab[h2].normal ) h3 = h1+tab[h2].adr;
						else h3 = s[h1+tab[h2].adr].i;
						
						switch (tab[h2].typ){
							case 1: printf("%d\n", s[h3].i); break;
							case 2: printf("%f\n", s[h3].r); break;
							case 3: printf("%d\n", s[h3].b); break;
							case 4: printf("%c\n", s[h3].c); break;
						}//switch
					}//if testtyp
				h2 = tab[h2].link;
			}//end while
			h1 = s[h1+3].i;
		}while(h1 >= 0);
	}//end if(ps!=fin)
	printf("\n"); printf("%d steps\n", ocnt);
}/*end interpret*/