#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#include <math.h>
#include <time.h>

/* ================================================================
   MS BASIC-80 Full C Port
   Ported from Z80 assembly disassembly (FNCTAB/WORDS/EVAL/NEWSTT)
   ================================================================ */

#define MAXLINES  2000
#define MAXBUF    512
#define MAXVARS   512
#define MAXARR    64
#define MAXARRLEN 1024
#define MAXSTACK  256
#define MAXDATA   2048
#define MAXSTR    256
#define MAXFILES  8

/* ---- Program storage ---- */
typedef struct { int num; char text[MAXBUF]; } Line;
Line program[MAXLINES];
int prog_cnt = 0;

/* ---- Variable types ---- */
#define TYPE_INT  2
#define TYPE_SNG  4
#define TYPE_STR  3

typedef struct {
    char name[MAXSTR];
    int  type;
    double num;
    char str[MAXSTR];
} Var;

Var variables[MAXVARS];
int var_cnt = 0;

/* ---- Arrays ---- */
typedef struct {
    char name[MAXSTR];
    int  type;
    int  dims[4];
    int  ndims;
    int  base; /* OPTION BASE */
    double *nums;
    char   (*strs)[MAXSTR];
} Arr;

Arr arrays[MAXARR];
int arr_cnt = 0;
int option_base = 0;

/* ---- DATA pool (FDTLP) ---- */
char data_pool[MAXDATA][MAXSTR];
int  data_count = 0;
int  data_pos   = 0;

/* ---- GOSUB stack (BAKSTK) ---- */
int call_stack[MAXSTACK];
int call_sp = 0;

/* ---- FOR/NEXT stack ---- */
typedef struct {
    int  var_idx;
    double limit;
    double step;
    int  line_idx;
} ForEntry;
ForEntry for_stack[MAXSTACK];
int for_sp = 0;

/* ---- WHILE/WEND stack ---- */
int while_stack[MAXSTACK];
int while_sp = 0;

/* ---- ON ERROR ---- */
int on_error_line = -1;
int err_number    = 0;
int err_line      = 0;

/* ---- Globals ---- */
double fac;
int    cur_line_idx;
int    running;
int    tron_flag = 0;
int    null_count = 0;  /* NULL() */
char   last_inkey = 0;
int    cont_idx = -1;   /* for CONT */

/* ---- File handles (OPEN/CLOSE) ---- */
FILE *file_handles[MAXFILES];
char file_modes[MAXFILES]; /* 'I','O','A','R' */

/* ============================================================
   UTILS
   ============================================================ */
static void skip_ws(char **p) { while (**p == ' ' || **p == '\t') (*p)++; }

static char *strupr_local(char *s) {
    for (char *p = s; *p; p++) *p = toupper(*p);
    return s;
}

/* ============================================================
   LINE MANAGEMENT (SRCHLN / INSERT)
   ============================================================ */
int find_line(int num) {
    for (int i = 0; i < prog_cnt; i++)
        if (program[i].num == num) return i;
    return -1;
}

void insert_line(int num, char *text) {
    for (int i = 0; i < prog_cnt; i++) {
        if (program[i].num == num) {
            if (!text || !*text) {
                for (int j = i; j < prog_cnt-1; j++) program[j] = program[j+1];
                prog_cnt--; return;
            }
            strncpy(program[i].text, text, MAXBUF-1);
            return;
        }
    }
    if (!text || !*text) return;
    program[prog_cnt].num = num;
    strncpy(program[prog_cnt].text, text, MAXBUF-1);
    prog_cnt++;
    for (int i = prog_cnt-1; i > 0 && program[i].num < program[i-1].num; i--) {
        Line tmp = program[i]; program[i] = program[i-1]; program[i-1] = tmp;
    }
}

/* ============================================================
   VARIABLE MANAGEMENT (PTRGET / GETVAR)
   ============================================================ */
int ptrget(const char *name) {
    for (int i = 0; i < var_cnt; i++)
        if (strcasecmp(name, variables[i].name) == 0) return i;
    strncpy(variables[var_cnt].name, name, MAXSTR-1);
    variables[var_cnt].type = TYPE_SNG;
    variables[var_cnt].num  = 0;
    variables[var_cnt].str[0] = 0;
    return var_cnt++;
}

int is_str_var(const char *name) {
    return name[strlen(name)-1] == '$';
}

/* ============================================================
   ARRAY MANAGEMENT (DIM / SBSCPT)
   ============================================================ */
Arr *find_arr(const char *name) {
    for (int i = 0; i < arr_cnt; i++)
        if (strcasecmp(name, arrays[i].name) == 0) return &arrays[i];
    return NULL;
}

Arr *make_arr(const char *name, int *dims, int ndims) {
    Arr *a = &arrays[arr_cnt++];
    strncpy(a->name, name, MAXSTR-1);
    a->ndims = ndims; a->base = option_base;
    int total = 1;
    for (int i = 0; i < ndims; i++) { a->dims[i] = dims[i]+1; total *= (dims[i]+1); }
    a->type = is_str_var(name) ? TYPE_STR : TYPE_SNG;
    if (a->type == TYPE_STR) a->strs = calloc(total, sizeof(*a->strs));
    else a->nums = calloc(total, sizeof(double));
    return a;
}

/* ============================================================
   EXPRESSION PARSER (EVAL / OPRND / PRITAB)
   Full: + - * / ^ unary- relational AND OR NOT
   Functions: ABS SQR RND SIN COS TAN ATN LOG EXP INT FIX SGN
              LEN VAL ASC CHR$ STR$ LEFT$ RIGHT$ MID$ SPACE$
              HEX$ OCT$ CINT CSNG CDBL INSTR STRING$ FRE POS
   ============================================================ */
double expr(char **p);
void   run_from(int idx);
void   execute_stmt(char *p);
void   basic_error(int code, char *msg);

static char str_result[MAXSTR]; /* scratch for string functions */

static double parse_string_fn(char **p) {
    /* Returns 0, result in str_result */
    str_result[0] = 0;
    return 0;
}

/* Parse a string literal or string expression, result -> str_result */
static void parse_str_expr(char **p, char *out) {
    skip_ws(p);
    if (**p == '"') {
        (*p)++; int i=0;
        while (**p && **p != '"') out[i++] = *(*p)++;
        out[i]=0; if(**p=='"')(*p)++;
    } else if (isalpha(**p)) {
        char name[MAXSTR]={0}; char *q=*p;
        int i=0;
        while (isalnum(**p) || **p=='$' || **p=='_') name[i++]=*(*p)++;
        name[i]=0;
        if (is_str_var(name)) {
            strcpy(out, variables[ptrget(name)].str);
        } else { *p=q; sprintf(out,"%g",expr(p)); }
    } else { sprintf(out,"%g",expr(p)); }
}

static double primary(char **p) {
    skip_ws(p);
    double x = 0;
    if (**p == '-') { (*p)++; return -primary(p); }
    if (**p == '+') { (*p)++; return primary(p); }
    if (**p == '(') { (*p)++; x=expr(p); skip_ws(p); if(**p==')')(*p)++; return x; }

    /* Functions */
    #define MATHFN1(nm,fn) if(strncasecmp(*p,nm"(",strlen(nm)+1)==0){*p+=strlen(nm)+1;x=fn(expr(p));skip_ws(p);if(**p==')')(*p)++;return x;}
    MATHFN1("ABS",fabs) MATHFN1("SQR",sqrt) MATHFN1("SIN",sin)
    MATHFN1("COS",cos)  MATHFN1("TAN",tan)  MATHFN1("ATN",atan)
    MATHFN1("LOG",log)  MATHFN1("EXP",exp)  MATHFN1("INT",floor)
    MATHFN1("FIX",trunc)
    #undef MATHFN1

    if (strncasecmp(*p,"SGN(",4)==0){ *p+=4; x=expr(p); skip_ws(p); if(**p==')')(*p)++; return (x>0)-(x<0); }
    if (strncasecmp(*p,"RND(",4)==0){ *p+=4; double a=expr(p); skip_ws(p); if(**p==')')(*p)++; (void)a; return (double)rand()/RAND_MAX; }
    if (strncasecmp(*p,"CINT(",5)==0){ *p+=5; x=round(expr(p)); skip_ws(p); if(**p==')')(*p)++; return (int)x; }
    if (strncasecmp(*p,"CSNG(",5)==0){ *p+=5; x=expr(p); skip_ws(p); if(**p==')')(*p)++; return (float)x; }
    if (strncasecmp(*p,"CDBL(",5)==0){ *p+=5; x=expr(p); skip_ws(p); if(**p==')')(*p)++; return x; }
    if (strncasecmp(*p,"FRE(",4)==0) { *p+=4; expr(p); skip_ws(p); if(**p==')')(*p)++; return 60000; }
    if (strncasecmp(*p,"POS(",4)==0) { *p+=4; expr(p); skip_ws(p); if(**p==')')(*p)++; return 0; }
    if (strncasecmp(*p,"LEN(",4)==0) { *p+=4; char tmp[MAXSTR]; parse_str_expr(p,tmp); skip_ws(p); if(**p==')')(*p)++; return strlen(tmp); }
    if (strncasecmp(*p,"ASC(",4)==0) { *p+=4; char tmp[MAXSTR]; parse_str_expr(p,tmp); skip_ws(p); if(**p==')')(*p)++; return tmp[0]; }
    if (strncasecmp(*p,"VAL(",4)==0) { *p+=4; char tmp[MAXSTR]; parse_str_expr(p,tmp); skip_ws(p); if(**p==')')(*p)++; return atof(tmp); }
    if (strncasecmp(*p,"PEEK(",5)==0){ *p+=5; x=expr(p); skip_ws(p); if(**p==')')(*p)++; return 0; } /* stub */
    if (strncasecmp(*p,"INP(",4)==0) { *p+=4; x=expr(p); skip_ws(p); if(**p==')')(*p)++; return 0; } /* stub */
    if (strncasecmp(*p,"LPOS(",5)==0){ *p+=5; x=expr(p); skip_ws(p); if(**p==')')(*p)++; return 0; }

    if (strncasecmp(*p,"INSTR(",6)==0) {
        *p+=6; double start=1; char h[MAXSTR],n[MAXSTR];
        /* INSTR([start,] hay, needle) */
        char *save=*p; double t=expr(p); skip_ws(p);
        if (**p==',') { start=t; (*p)++; parse_str_expr(p,h); }
        else { *p=save; parse_str_expr(p,h); }
        skip_ws(p); if(**p==',')(*p)++;
        parse_str_expr(p,n);
        skip_ws(p); if(**p==')')(*p)++;
        char *found=strstr(h+(int)start-1,n);
        return found ? (found-h+1) : 0;
    }

    /* NOT */
    if (strncasecmp(*p,"NOT",3)==0 && !isalnum((*p)[3])) { *p+=3; return ~(int)primary(p); }

    /* Number literal */
    if (isdigit(**p) || **p=='.') {
        char *end; x=strtod(*p,&end); *p=end; return x;
    }

    /* Hex &H / Octal &O */
    if (**p=='&') {
        (*p)++;
        if (toupper(**p)=='H') { (*p)++; x=(double)strtol(*p,p,16); return x; }
        if (toupper(**p)=='O') { (*p)++; x=(double)strtol(*p,p,8);  return x; }
        x=(double)strtol(*p,p,8); return x;
    }

    /* Variable or array element */
    if (isalpha(**p)) {
        char name[MAXSTR]={0}; int i=0;
        while (isalnum(**p)||**p=='$'||**p=='_') name[i++]=*(*p)++;
        name[i]=0;
        skip_ws(p);
        /* Array element */
        if (**p=='(') {
            (*p)++;
            int idx[4]={0}; int nd=0;
            while (**p && **p!=')') {
                idx[nd++]=(int)expr(p); skip_ws(p);
                if(**p==',')(*p)++;
            }
            if(**p==')')(*p)++;
            Arr *a = find_arr(name);
            if (!a) { /* auto-dim 0..10 */ int d=10; a=make_arr(name,&d,1); }
            int flat=0;
            if (nd>=1) flat=idx[0]-option_base;
            if (nd>=2) flat=flat*(a->dims[1])+idx[1]-option_base;
            if (flat<0) flat=0;
            if (a->type==TYPE_STR) { /* str arrays not returned as number */ return 0; }
            else return a->nums[flat];
        }
        return variables[ptrget(name)].num;
    }
    return 0;
}

static double power_e(char **p) {
    double x=primary(p); skip_ws(p);
    if (**p=='^') { (*p)++; x=pow(x,primary(p)); }
    return x;
}
static double term(char **p) {
    double x=power_e(p); skip_ws(p);
    while(**p=='*'||**p=='/') { char op=*(*p)++; double y=power_e(p); x=(op=='*')?x*y:(y?x/y:(basic_error(11,"Division by zero"),1.0)); skip_ws(p); }
    return x;
}
static double add_sub(char **p) {
    double x=term(p); skip_ws(p);
    while(**p=='+'||**p=='-') { char op=*(*p)++; double y=term(p); x=(op=='+')?x+y:x-y; skip_ws(p); }
    return x;
}
static double relational(char **p) {
    double x=add_sub(p); skip_ws(p);
    if (strncmp(*p,"<>",2)==0){*p+=2;return x!=add_sub(p);}
    if (strncmp(*p,"<=",2)==0){*p+=2;return x<=add_sub(p);}
    if (strncmp(*p,">=",2)==0){*p+=2;return x>=add_sub(p);}
    if (**p=='<'){(*p)++;return x<add_sub(p);}
    if (**p=='>'){(*p)++;return x>add_sub(p);}
    if (**p=='='){(*p)++;return x==add_sub(p);}
    return x;
}
static double and_or(char **p) {
    double x=relational(p); skip_ws(p);
    while(1){
        if (strncasecmp(*p,"AND",3)==0&&!isalnum((*p)[3])){ *p+=3; x=(int)x&(int)relational(p); }
        else if(strncasecmp(*p,"OR",2)==0&&!isalnum((*p)[2])){ *p+=2; x=(int)x|(int)relational(p); }
        else if(strncasecmp(*p,"XOR",3)==0&&!isalnum((*p)[3])){ *p+=3; x=(int)x^(int)relational(p); }
        else break;
        skip_ws(p);
    }
    return x;
}
double expr(char **p) { return fac=and_or(p); }

/* String expression: result in out */
static void str_expr(char **p, char *out) {
    skip_ws(p);
    /* CHR$ */
    if (strncasecmp(*p,"CHR$(",5)==0){ *p+=5; int c=(int)expr(p); skip_ws(p); if(**p==')')(*p)++; out[0]=c; out[1]=0; return; }
    /* STR$ */
    if (strncasecmp(*p,"STR$(",5)==0){ *p+=5; double v=expr(p); skip_ws(p); if(**p==')')(*p)++; sprintf(out,"%g",v); return; }
    /* LEFT$ */
    if (strncasecmp(*p,"LEFT$(",6)==0){ *p+=6; char s[MAXSTR]; parse_str_expr(p,s); skip_ws(p); if(**p==',')(*p)++; int n=(int)expr(p); skip_ws(p); if(**p==')')(*p)++; strncpy(out,s,n); out[n]=0; return; }
    /* RIGHT$ */
    if (strncasecmp(*p,"RIGHT$(",7)==0){ *p+=7; char s[MAXSTR]; parse_str_expr(p,s); skip_ws(p); if(**p==',')(*p)++; int n=(int)expr(p); skip_ws(p); if(**p==')')(*p)++; int l=strlen(s); int st=l-n; if(st<0)st=0; strcpy(out,s+st); return; }
    /* MID$ */
    if (strncasecmp(*p,"MID$(",5)==0){ *p+=5; char s[MAXSTR]; parse_str_expr(p,s); skip_ws(p); if(**p==',')(*p)++; int st=(int)expr(p)-1; skip_ws(p); int n=strlen(s); if(**p==','){ (*p)++; n=(int)expr(p); } skip_ws(p); if(**p==')')(*p)++; if(st<0)st=0; strncpy(out,s+st,n); out[n]=0; return; }
    /* SPACE$ */
    if (strncasecmp(*p,"SPACE$(",7)==0){ *p+=7; int n=(int)expr(p); skip_ws(p); if(**p==')')(*p)++; memset(out,' ',n); out[n]=0; return; }
    /* STRING$ */
    if (strncasecmp(*p,"STRING$(",8)==0){ *p+=8; int n=(int)expr(p); skip_ws(p); if(**p==',')(*p)++; char tmp[MAXSTR]; if(**p=='"'){ parse_str_expr(p,tmp); memset(out,tmp[0],n); } else { int c=(int)expr(p); memset(out,c,n); } out[n]=0; skip_ws(p); if(**p==')')(*p)++; return; }
    /* HEX$ */
    if (strncasecmp(*p,"HEX$(",5)==0){ *p+=5; int v=(int)expr(p); skip_ws(p); if(**p==')')(*p)++; sprintf(out,"%X",v); return; }
    /* OCT$ */
    if (strncasecmp(*p,"OCT$(",5)==0){ *p+=5; int v=(int)expr(p); skip_ws(p); if(**p==')')(*p)++; sprintf(out,"%o",v); return; }
    /* MKI$ MKS$ MKD$ */
    if (strncasecmp(*p,"MKI$(",5)==0){ *p+=5; int v=(int)expr(p); skip_ws(p); if(**p==')')(*p)++; memcpy(out,&v,2); out[2]=0; return; }
    if (strncasecmp(*p,"MKS$(",5)==0){ *p+=5; float v=(float)expr(p); skip_ws(p); if(**p==')')(*p)++; memcpy(out,&v,4); out[4]=0; return; }
    if (strncasecmp(*p,"MKD$(",5)==0){ *p+=5; double v=expr(p); skip_ws(p); if(**p==')')(*p)++; memcpy(out,&v,8); out[8]=0; return; }
    /* INKEY$ */
    if (strncasecmp(*p,"INKEY$",6)==0){ *p+=6; out[0]=last_inkey; out[1]=0; last_inkey=0; return; }
    /* Fallthrough: parse as string var or literal */
    parse_str_expr(p, out);
}

/* ============================================================
   COLLECT DATA (FDTLP)
   ============================================================ */
void collect_data() {
    data_count=0; data_pos=0;
    for (int i=0;i<prog_cnt;i++) {
        char *p=program[i].text;
        while (*p) {
            if (strncasecmp(p,"DATA",4)==0) {
                p+=4;
                while (*p && *p!='\n') {
                    skip_ws(&p);
                    if (*p==',') { p++; continue; }
                    if (!*p) break;
                    char *dst=data_pool[data_count];
                    if (*p=='"') { p++; int i2=0; while(*p&&*p!='"') dst[i2++]=*p++; dst[i2]=0; if(*p=='"')p++; }
                    else { int i2=0; while(*p&&*p!=','&&*p!='\n') dst[i2++]=*p++; dst[i2]=0; }
                    data_count++;
                    skip_ws(&p);
                }
                break;
            }
            p++;
        }
    }
}

/* ============================================================
   ERROR HANDLING (ERRORREPORT)
   ============================================================ */
void basic_error(int code, char *msg) {
    fprintf(stderr,"?%s error in %d\n", msg, (prog_cnt>0 && cur_line_idx<prog_cnt)?program[cur_line_idx].num:0);
    err_number=code;
    if (on_error_line>=0) { cur_line_idx=find_line(on_error_line); running=2; return; }
    running=0;
}

/* ============================================================
   PRINT USING (USING / PUFOUT) - basic implementation
   ============================================================ */
static void print_using(char *fmt, double val) {
    /* Handle # . , + - $ simple format chars */
    char buf[MAXBUF]; int w=0,d=0;
    for (char *f=fmt;*f;f++) if(*f=='#') w++; else if(*f=='.') { for(char *g=f+1;*g=='#';g++) d++; break; }
    if (d>0) printf("%*.*f",w,d,val);
    else printf("%*g",w,val);
}

/* ============================================================
   WRITE statement (csv output)
   ============================================================ */
static void do_write(char **p, FILE *fp) {
    while (**p) {
        skip_ws(p);
        if (**p=='"' || (isalpha(**p) && is_str_var(*p))) {
            char s[MAXSTR]; str_expr(p,s);
            fprintf(fp,"\"%s\"",s);
        } else {
            fprintf(fp,"%g",expr(p));
        }
        skip_ws(p);
        if (**p==',') { fprintf(fp,","); (*p)++; }
        else break;
    }
    fprintf(fp,"\n");
}

/* ============================================================
   EXECUTE ONE STATEMENT (NEWSTT / EXEC / FNCTAB)
   ============================================================ */
void execute_stmt(char *p) {
    skip_ws(&p);
    if (!*p) return;

    /* REM / ' */
    if (strncasecmp(p,"REM",3)==0||*p=='\'') return;

    /* PRINT / LPRINT */
    if (strncasecmp(p,"LPRINT",6)==0||strncasecmp(p,"PRINT",5)==0) {
        FILE *fp=stdout; int is_lp=(strncasecmp(p,"LPRINT",6)==0);
        p += is_lp?6:5;
        /* PRINT USING */
        if (strncasecmp(p," USING",6)==0||strncasecmp(p,"USING",5)==0) {
            if(*p==' ')p++; p+=5; skip_ws(&p);
            char fmt[MAXBUF]; str_expr(&p,fmt);
            skip_ws(&p); if(*p==';')p++;
            double v=expr(&p);
            print_using(fmt,v);
            fprintf(fp,"\n"); return;
        }
        int newline=1;
        while (*p) {
            skip_ws(&p);
            if (!*p) break;
            if (*p==';') { p++; newline=0; continue; }
            if (*p==',') { fprintf(fp,"\t"); p++; newline=0; continue; }
            /* TAB( */
            if (strncasecmp(p,"TAB(",4)==0) { p+=4; int n=(int)expr(&p); skip_ws(&p); if(*p==')')p++; for(int i=0;i<n;i++) fputc(' ',fp); newline=0; continue; }
            /* SPC( */
            if (strncasecmp(p,"SPC(",4)==0) { p+=4; int n=(int)expr(&p); skip_ws(&p); if(*p==')')p++; for(int i=0;i<n;i++) fputc(' ',fp); newline=0; continue; }
            newline=1;
            if (*p=='"'||(isalpha(*p)&&is_str_var(p))) {
                char s[MAXSTR]; str_expr(&p,s); fprintf(fp,"%s",s);
            } else {
                double v=expr(&p); 
                if (v==(long)v) fprintf(fp,"%.0f",v); else fprintf(fp,"%g",v);
                fputc(' ',fp);
            }
            skip_ws(&p);
        }
        if (newline) fprintf(fp,"\n");
        return;
    }

    /* INPUT / LINE INPUT */
    if (strncasecmp(p,"LINE INPUT",10)==0) {
        p+=10; skip_ws(&p); if(*p=='#'){p++; expr(&p); skip_ws(&p); if(*p==',')p++;} /* file# stub */
        char name[MAXSTR]={0}; int i=0; skip_ws(&p);
        while(isalnum(*p)||*p=='$') name[i++]=*p++;
        name[i]=0;
        char line[MAXBUF]; if(!fgets(line,MAXBUF,stdin)) line[0]=0;
        line[strcspn(line,"\n")]=0;
        int vi=ptrget(name); strncpy(variables[vi].str,line,MAXSTR-1); variables[vi].type=TYPE_STR;
        return;
    }
    if (strncasecmp(p,"INPUT",5)==0) {
        p+=5; skip_ws(&p);
        int file_no=-1;
        if (*p=='#') { p++; file_no=(int)expr(&p); skip_ws(&p); if(*p==',')p++; }
        char prompt[MAXBUF]="? ";
        if (*p=='"') { p++; int i=0; while(*p&&*p!='"') prompt[i++]=*p++; prompt[i]=0; if(*p=='"')p++; if(*p==';'||*p==',')p++; strcat(prompt,"? "); }
        while (*p) {
            skip_ws(&p);
            if (*p==',') { p++; continue; }
            char name[MAXSTR]={0}; int i=0;
            while(isalnum(*p)||*p=='$') name[i++]=*p++;
            name[i]=0;
            if (!name[0]) break;
            printf("%s",prompt); prompt[0]=0; strcpy(prompt,"");
            char ibuf[MAXBUF];
            if (file_no>=0 && file_handles[file_no]) { fgets(ibuf,MAXBUF,file_handles[file_no]); }
            else { fgets(ibuf,MAXBUF,stdin); }
            ibuf[strcspn(ibuf,"\n")]=0;
            int vi=ptrget(name);
            if (is_str_var(name)) { strncpy(variables[vi].str,ibuf,MAXSTR-1); variables[vi].type=TYPE_STR; }
            else { variables[vi].num=atof(ibuf); variables[vi].type=TYPE_SNG; }
            skip_ws(&p);
        }
        return;
    }

    /* LET / assignment */
    if (strncasecmp(p,"LET",3)==0&&!isalnum(p[3])) p+=3;
    if (isalpha(*p)) {
        char name[MAXSTR]={0}; char *save=p; int i=0;
        while(isalnum(*p)||*p=='$') name[i++]=*p++;
        name[i]=0;
        skip_ws(&p);
        /* Array assignment */
        if (*p=='(') {
            (*p==0); p++;
            int idx[4]={0}; int nd=0;
            while(*p&&*p!=')') { idx[nd++]=(int)expr(&p); skip_ws(&p); if(*p==',')p++; }
            if(*p==')')p++;
            skip_ws(&p); if(*p=='=')p++;
            Arr *a=find_arr(name);
            if(!a){int d=10;a=make_arr(name,&d,1);}
            int flat=idx[0]-option_base;
            if (nd>=2) flat=flat*(a->dims[1])+idx[1]-option_base;
            if (flat<0) flat=0;
            if (a->type==TYPE_STR){char s[MAXSTR];str_expr(&p,s);strncpy(a->strs[flat],s,MAXSTR-1);}
            else a->nums[flat]=expr(&p);
            return;
        }
        if (*p=='=') {
            p++;
            int vi=ptrget(name);
            if (is_str_var(name)) {
                char s[MAXSTR]; str_expr(&p,s);
                strncpy(variables[vi].str,s,MAXSTR-1);
                variables[vi].type=TYPE_STR;
            } else {
                variables[vi].num=expr(&p);
                variables[vi].type=TYPE_SNG;
            }
            return;
        }
        p=save;
    }

    /* IF / THEN / ELSE */
    if (strncasecmp(p,"IF",2)==0&&!isalnum(p[2])) {
        p+=2; skip_ws(&p);
        double cond=expr(&p);
        skip_ws(&p);
        if (strncasecmp(p,"THEN",4)==0&&!isalnum(p[4])) p+=4;
        skip_ws(&p);
        /* THEN line_number */
        if (isdigit(*p)) {
            int tgt=(int)strtol(p,&p,10);
            if (cond) { int idx=find_line(tgt); if(idx>=0){cur_line_idx=idx;running=2;} } 
            else {
                /* find ELSE */
                skip_ws(&p);
                if (strncasecmp(p,"ELSE",4)==0) { p+=4; skip_ws(&p);
                    if(isdigit(*p)){ int t=(int)strtol(p,&p,10); int idx=find_line(t); if(idx>=0){cur_line_idx=idx;running=2;}}
                    else execute_stmt(p);
                }
            }
            return;
        }
        char *else_p=NULL;
        /* find ELSE in remainder */
        char *scan=p; int depth=0;
        while(*scan){
            if(*scan=='(')depth++; else if(*scan==')')depth--;
            if(depth==0&&strncasecmp(scan,"ELSE",4)==0&&!isalnum(scan[4])&&!isalnum(scan[-1])){ else_p=scan; break; }
            scan++;
        }
        if (cond) { char tmp[MAXBUF]; if(else_p){int len=else_p-p;strncpy(tmp,p,len);tmp[len]=0;execute_stmt(tmp);}else execute_stmt(p); }
        else if (else_p) { execute_stmt(else_p+4); }
        return;
    }

    /* GOTO */
    if (strncasecmp(p,"GOTO",4)==0&&!isalnum(p[4])) {
        p+=4; int tgt=(int)expr(&p);
        int idx=find_line(tgt);
        if(idx<0){basic_error(8,"Undefined line");return;}
        cur_line_idx=idx; running=2; return;
    }

    /* GOSUB */
    if (strncasecmp(p,"GOSUB",5)==0&&!isalnum(p[5])) {
        p+=5; int tgt=(int)expr(&p);
        int idx=find_line(tgt);
        if(idx<0){basic_error(8,"Undefined line");return;}
        call_stack[call_sp++]=cur_line_idx+1;
        cur_line_idx=idx; running=2; return;
    }

    /* RETURN */
    if (strncasecmp(p,"RETURN",6)==0&&!isalnum(p[6])) {
        if(call_sp<=0){basic_error(3,"RETURN without GOSUB");return;}
        cur_line_idx=call_stack[--call_sp]; running=2; return;
    }

    /* ON GOTO / ON GOSUB / ON ERROR */
    if (strncasecmp(p,"ON",2)==0&&!isalnum(p[2])) {
        p+=2; skip_ws(&p);
        if (strncasecmp(p,"ERROR",5)==0) {
            p+=5; skip_ws(&p);
            if (strncasecmp(p,"GOTO",4)==0){p+=4; on_error_line=(int)expr(&p);}
            else if(strncasecmp(p,"RESUME",6)==0){p+=6;skip_ws(&p);if(strncasecmp(p,"NEXT",4)==0)p+=4;}
            return;
        }
        double n=expr(&p); skip_ws(&p);
        int is_sub=(strncasecmp(p,"GOSUB",5)==0);
        p += is_sub?5:4;
        int targets[64]; int tc=0;
        while(*p){skip_ws(&p);if(!isdigit(*p))break;targets[tc++]=(int)strtol(p,&p,10);skip_ws(&p);if(*p==',')p++;}
        int ni=(int)n-1;
        if(ni>=0&&ni<tc){
            int idx=find_line(targets[ni]);
            if(idx>=0){
                if(is_sub){call_stack[call_sp++]=cur_line_idx+1;}
                cur_line_idx=idx; running=2;
            }
        }
        return;
    }

    /* FOR */
    if (strncasecmp(p,"FOR",3)==0&&!isalnum(p[3])) {
        p+=3; skip_ws(&p);
        char name[MAXSTR]={0}; int i=0;
        while(isalnum(*p)||*p=='$') name[i++]=*p++;
        name[i]=0;
        skip_ws(&p); if(*p=='=')p++;
        double start=expr(&p);
        skip_ws(&p); if(strncasecmp(p,"TO",2)==0&&!isalnum(p[2]))p+=2;
        double limit=expr(&p);
        double step=1.0;
        skip_ws(&p); if(strncasecmp(p,"STEP",4)==0&&!isalnum(p[4])){p+=4;step=expr(&p);}
        int vi=ptrget(name); variables[vi].num=start; variables[vi].type=TYPE_SNG;
        for_stack[for_sp].var_idx=vi;
        for_stack[for_sp].limit=limit;
        for_stack[for_sp].step=step;
        for_stack[for_sp].line_idx=cur_line_idx;
        for_sp++;
        return;
    }

    /* NEXT */
    if (strncasecmp(p,"NEXT",4)==0&&!isalnum(p[4])) {
        if(for_sp<=0){basic_error(1,"NEXT without FOR");return;}
        ForEntry *fe=&for_stack[for_sp-1];
        variables[fe->var_idx].num+=fe->step;
        if((fe->step>0&&variables[fe->var_idx].num<=fe->limit)||
           (fe->step<0&&variables[fe->var_idx].num>=fe->limit)){
            cur_line_idx=fe->line_idx; running=2;
        } else for_sp--;
        return;
    }

    /* WHILE */
    if (strncasecmp(p,"WHILE",5)==0&&!isalnum(p[5])) {
        p+=5;
        if (!expr(&p)) {
            /* skip to WEND */
            int depth=1;
            while(++cur_line_idx<prog_cnt&&depth>0){
                if(strstr(program[cur_line_idx].text,"WHILE"))depth++;
                if(strstr(program[cur_line_idx].text,"WEND"))depth--;
            }
        } else {
            while_stack[while_sp++]=cur_line_idx;
        }
        return;
    }

    /* WEND */
    if (strncasecmp(p,"WEND",4)==0&&!isalnum(p[4])) {
        if(while_sp<=0){basic_error(23,"WEND without WHILE");return;}
        cur_line_idx=while_stack[--while_sp]-1;
        running=2; return;
    }

    /* DATA */
    if (strncasecmp(p,"DATA",4)==0) return;

    /* READ */
    if (strncasecmp(p,"READ",4)==0&&!isalnum(p[4])) {
        p+=4;
        while(*p){
            skip_ws(&p); if(*p==',')p++; skip_ws(&p); if(!*p)break;
            char name[MAXSTR]={0}; int i=0;
            while(isalnum(*p)||*p=='$') name[i++]=*p++;
            name[i]=0; if(!name[0])break;
            if(data_pos>=data_count){basic_error(4,"Out of DATA");return;}
            int vi=ptrget(name);
            if(is_str_var(name)){strncpy(variables[vi].str,data_pool[data_pos++],MAXSTR-1);variables[vi].type=TYPE_STR;}
            else{variables[vi].num=atof(data_pool[data_pos++]);variables[vi].type=TYPE_SNG;}
        }
        return;
    }

    /* RESTORE */
    if (strncasecmp(p,"RESTORE",7)==0) { 
        p+=7; skip_ws(&p);
        if(isdigit(*p)){int tgt=(int)strtol(p,&p,10);(void)tgt;} /* stub: restore to line */
        data_pos=0; return;
    }

    /* DIM */
    if (strncasecmp(p,"DIM",3)==0&&!isalnum(p[3])) {
        p+=3;
        while(*p){
            skip_ws(&p); if(*p==',')p++; skip_ws(&p); if(!*p)break;
            char name[MAXSTR]={0}; int i=0;
            while(isalnum(*p)||*p=='$') name[i++]=*p++;
            name[i]=0;
            skip_ws(&p);
            int dims[4]={10,10,10,10}; int ndims=0;
            if(*p=='('){
                p++;
                while(*p&&*p!=')'){skip_ws(&p);dims[ndims++]=(int)expr(&p);skip_ws(&p);if(*p==',')p++;}
                if(*p==')')p++;
            }
            if(ndims==0)ndims=1;
            make_arr(name,dims,ndims);
        }
        return;
    }

    /* SWAP */
    if (strncasecmp(p,"SWAP",4)==0&&!isalnum(p[4])) {
        p+=4; skip_ws(&p);
        char n1[MAXSTR]={0}; int i=0; while(isalnum(*p)||*p=='$') n1[i++]=*p++; n1[i]=0;
        skip_ws(&p); if(*p==',')p++; skip_ws(&p);
        char n2[MAXSTR]={0}; i=0; while(isalnum(*p)||*p=='$') n2[i++]=*p++; n2[i]=0;
        int v1=ptrget(n1),v2=ptrget(n2);
        double tmp=variables[v1].num; variables[v1].num=variables[v2].num; variables[v2].num=tmp;
        char ts[MAXSTR]; strcpy(ts,variables[v1].str); strcpy(variables[v1].str,variables[v2].str); strcpy(variables[v2].str,ts);
        return;
    }

    /* POKE */
    if (strncasecmp(p,"POKE",4)==0&&!isalnum(p[4])) {
        p+=4; expr(&p); skip_ws(&p); if(*p==',')p++; expr(&p); /* stub */
        return;
    }

    /* WAIT */
    if (strncasecmp(p,"WAIT",4)==0&&!isalnum(p[4])) { p+=4; expr(&p); skip_ws(&p); if(*p==',')p++; expr(&p); return; }

    /* OUT */
    if (strncasecmp(p,"OUT",3)==0&&!isalnum(p[3])) { p+=3; expr(&p); skip_ws(&p); if(*p==',')p++; expr(&p); return; }

    /* LSET / RSET */
    if (strncasecmp(p,"LSET",4)==0&&!isalnum(p[4])) {
        p+=4; skip_ws(&p); char name[MAXSTR]={0}; int i=0;
        while(isalnum(*p)||*p=='$') name[i++]=*p++;
        name[i]=0; skip_ws(&p); if(*p=='=')p++;
        char s[MAXSTR]; str_expr(&p,s);
        int vi=ptrget(name); strncpy(variables[vi].str,s,MAXSTR-1); variables[vi].type=TYPE_STR;
        return;
    }
    if (strncasecmp(p,"RSET",4)==0&&!isalnum(p[4])) {
        p+=4; skip_ws(&p); char name[MAXSTR]={0}; int i=0;
        while(isalnum(*p)||*p=='$') name[i++]=*p++;
        name[i]=0; skip_ws(&p); if(*p=='=')p++;
        char s[MAXSTR]; str_expr(&p,s);
        int vi=ptrget(name); strncpy(variables[vi].str,s,MAXSTR-1); variables[vi].type=TYPE_STR;
        return;
    }

    /* WRITE */
    if (strncasecmp(p,"WRITE",5)==0&&!isalnum(p[5])) {
        p+=5; skip_ws(&p);
        FILE *fp=stdout; if(*p=='#'){p++;int fn=(int)expr(&p);skip_ws(&p);if(*p==',')p++;if(fn>=0&&fn<MAXFILES&&file_handles[fn])fp=file_handles[fn];}
        do_write(&p,fp); return;
    }

    /* OPEN */
    if (strncasecmp(p,"OPEN",4)==0&&!isalnum(p[4])) {
        p+=4; skip_ws(&p);
        char fname[MAXBUF]; str_expr(&p,fname); skip_ws(&p);
        char mode_str[8]="O";
        if(strncasecmp(p,"FOR",3)==0&&!isalnum(p[3])){
            p+=3; skip_ws(&p);
            if(strncasecmp(p,"INPUT",5)==0){strcpy(mode_str,"r");p+=5;}
            else if(strncasecmp(p,"OUTPUT",6)==0){strcpy(mode_str,"w");p+=6;}
            else if(strncasecmp(p,"APPEND",6)==0){strcpy(mode_str,"a");p+=6;}
            skip_ws(&p);
        }
        if(strncasecmp(p,"AS",2)==0&&!isalnum(p[2])){p+=2;skip_ws(&p);}
        if(*p=='#')p++;
        int fn=(int)expr(&p);
        if(fn>=0&&fn<MAXFILES){ if(file_handles[fn])fclose(file_handles[fn]); file_handles[fn]=fopen(fname,mode_str); }
        return;
    }

    /* CLOSE */
    if (strncasecmp(p,"CLOSE",5)==0&&!isalnum(p[5])) {
        p+=5; skip_ws(&p);
        if(!*p){for(int i=0;i<MAXFILES;i++){if(file_handles[i])fclose(file_handles[i]);file_handles[i]=NULL;}return;}
        while(*p){skip_ws(&p);if(*p=='#')p++;int fn=(int)expr(&p);if(fn>=0&&fn<MAXFILES&&file_handles[fn]){fclose(file_handles[fn]);file_handles[fn]=NULL;}skip_ws(&p);if(*p==',')p++;}
        return;
    }

    /* LOAD */
    if (strncasecmp(p,"LOAD",4)==0&&!isalnum(p[4])) {
        p+=4; skip_ws(&p); char fname[MAXBUF]; str_expr(&p,fname);
        FILE *f=fopen(fname,"r"); if(!f){fprintf(stderr,"?File not found: %s\n",fname);return;}
        char line[MAXBUF];
        while(fgets(line,MAXBUF,f)){
            line[strcspn(line,"\n")]=0;
            char *q=line; skip_ws(&q);
            if(isdigit(*q)){int num=(int)strtol(q,&q,10);skip_ws(&q);insert_line(num,q);}
        }
        fclose(f); collect_data(); return;
    }

    /* SAVE */
    if (strncasecmp(p,"SAVE",4)==0&&!isalnum(p[4])) {
        p+=4; skip_ws(&p); char fname[MAXBUF]; str_expr(&p,fname);
        FILE *f=fopen(fname,"w"); if(!f){fprintf(stderr,"?Cannot save\n");return;}
        for(int i=0;i<prog_cnt;i++) fprintf(f,"%d %s\n",program[i].num,program[i].text);
        fclose(f); return;
    }

    /* KILL */
    if (strncasecmp(p,"KILL",4)==0&&!isalnum(p[4])) {
        p+=4; skip_ws(&p); char fname[MAXBUF]; str_expr(&p,fname); remove(fname); return;
    }

    /* NAME */
    if (strncasecmp(p,"NAME",4)==0&&!isalnum(p[4])) {
        p+=4; skip_ws(&p); char old[MAXBUF],new_[MAXBUF];
        str_expr(&p,old); skip_ws(&p);
        if(strncasecmp(p,"AS",2)==0)p+=2; skip_ws(&p);
        str_expr(&p,new_); rename(old,new_); return;
    }

    /* FILES */
    if (strncasecmp(p,"FILES",5)==0&&!isalnum(p[5])) {
        system("ls"); return; /* stub */
    }

    /* WIDTH */
    if (strncasecmp(p,"WIDTH",5)==0&&!isalnum(p[5])) {
        p+=5; expr(&p); return; /* stub */
    }

    /* TRON / TROFF */
    if (strncasecmp(p,"TRON",4)==0&&!isalnum(p[4])) { tron_flag=1; return; }
    if (strncasecmp(p,"TROFF",5)==0&&!isalnum(p[5])) { tron_flag=0; return; }

    /* ERASE */
    if (strncasecmp(p,"ERASE",5)==0&&!isalnum(p[5])) {
        p+=5; skip_ws(&p); char name[MAXSTR]={0}; int i=0;
        while(isalnum(*p)||*p=='$') name[i++]=*p++;
        name[i]=0;
        for(int j=0;j<arr_cnt;j++) if(strcasecmp(arrays[j].name,name)==0){
            if(arrays[j].nums)free(arrays[j].nums);
            if(arrays[j].strs)free(arrays[j].strs);
            for(int k=j;k<arr_cnt-1;k++) arrays[k]=arrays[k+1]; arr_cnt--; break;
        }
        return;
    }

    /* RANDOMIZE */
    if (strncasecmp(p,"RANDOMIZE",9)==0&&!isalnum(p[9])) {
        p+=9; skip_ws(&p);
        if(*p) srand((unsigned)expr(&p)); else srand((unsigned)time(NULL));
        return;
    }

    /* OPTION BASE */
    if (strncasecmp(p,"OPTION",6)==0&&!isalnum(p[6])) {
        p+=6; skip_ws(&p);
        if(strncasecmp(p,"BASE",4)==0){p+=4;option_base=(int)expr(&p);}
        return;
    }

    /* DEF FN */
    if (strncasecmp(p,"DEF",3)==0&&!isalnum(p[3])) {
        /* stub - user functions not yet supported */
        return;
    }

    /* DEFSTR/DEFINT/DEFSNG/DEFDBL */
    if (strncasecmp(p,"DEFSTR",6)==0||strncasecmp(p,"DEFINT",6)==0||
        strncasecmp(p,"DEFSNG",6)==0||strncasecmp(p,"DEFDBL",6)==0) return; /* stub */

    /* RESUME */
    if (strncasecmp(p,"RESUME",6)==0&&!isalnum(p[6])) {
        p+=6; skip_ws(&p);
        if(strncasecmp(p,"NEXT",4)==0) cur_line_idx++;
        err_number=0; on_error_line=-1; running=1; return;
    }

    /* ERROR */
    if (strncasecmp(p,"ERROR",5)==0&&!isalnum(p[5])) {
        p+=5; int code=(int)expr(&p); basic_error(code,"User"); return;
    }

    /* DELETE */
    if (strncasecmp(p,"DELETE",6)==0&&!isalnum(p[6])) {
        p+=6; skip_ws(&p); int n1=(int)strtol(p,&p,10); int n2=n1;
        if(*p=='-'){p++;n2=(int)strtol(p,&p,10);}
        for(int i=n1;i<=n2;i++) insert_line(i,"");
        return;
    }

    /* RENUM */
    if (strncasecmp(p,"RENUM",5)==0&&!isalnum(p[5])) {
        p+=5; int start=10, step=10;
        skip_ws(&p); if(isdigit(*p)){start=(int)strtol(p,&p,10);skip_ws(&p);if(*p==','){p++;step=(int)strtol(p,&p,10);}}
        for(int i=0;i<prog_cnt;i++) program[i].num=start+i*step;
        return;
    }

    /* AUTO */
    if (strncasecmp(p,"AUTO",4)==0&&!isalnum(p[4])) { printf("[AUTO mode not supported interactively]\n"); return; }

    /* EDIT */
    if (strncasecmp(p,"EDIT",4)==0&&!isalnum(p[4])) {
        p+=4; skip_ws(&p); int n=(int)strtol(p,&p,10);
        int idx=find_line(n);
        if(idx>=0) printf("%d %s\n",program[idx].num,program[idx].text);
        return;
    }

    /* NULL */
    if (strncasecmp(p,"NULL",4)==0&&!isalnum(p[4])) { p+=4; null_count=(int)expr(&p); return; }

    /* CALL */
    if (strncasecmp(p,"CALL",4)==0&&!isalnum(p[4])) { p+=4; expr(&p); return; /* stub */ }

    /* CHAIN */
    if (strncasecmp(p,"CHAIN",5)==0&&!isalnum(p[5])) {
        p+=5; skip_ws(&p); char fname[MAXBUF]; str_expr(&p,fname);
        execute_stmt("NEW"); execute_stmt("LOAD");
        return;
    }

    /* SYSTEM */
    if (strncasecmp(p,"SYSTEM",6)==0&&!isalnum(p[6])) { printf("\n"); exit(0); }

    /* END / STOP */
    if (strncasecmp(p,"END",3)==0&&!isalnum(p[3])) { cont_idx=cur_line_idx; running=0; return; }
    if (strncasecmp(p,"STOP",4)==0&&!isalnum(p[4])) { printf("Break in %d\n", program[cur_line_idx].num); cont_idx=cur_line_idx+1; running=0; return; }

    /* CONT */
    if (strncasecmp(p,"CONT",4)==0&&!isalnum(p[4])) {
        if(cont_idx<0){printf("?Can't continue\n");return;}
        run_from(cont_idx); return;
    }

    /* LIST [n[-m]] */
    if (strncasecmp(p,"LIST",4)==0&&!isalnum(p[4])) {
        p+=4; skip_ws(&p);
        int n1=0,n2=999999;
        if(isdigit(*p)){n1=(int)strtol(p,&p,10);n2=n1;skip_ws(&p);if(*p=='-'){p++;if(isdigit(*p))n2=(int)strtol(p,&p,10);else n2=999999;}}
        for(int i=0;i<prog_cnt;i++) if(program[i].num>=n1&&program[i].num<=n2) printf("%d %s\n",program[i].num,program[i].text);
        return;
    }

    /* RUN */
    if (strncasecmp(p,"RUN",3)==0&&!isalnum(p[3])) {
        p+=3; skip_ws(&p); int start=0;
        if(isdigit(*p)){int n=(int)strtol(p,&p,10);start=find_line(n);if(start<0)start=0;}
        collect_data(); data_pos=0; call_sp=0; for_sp=0; while_sp=0; var_cnt=0; arr_cnt=0;
        run_from(start); return;
    }

    /* NEW */
    if (strncasecmp(p,"NEW",3)==0&&!isalnum(p[3])) {
        prog_cnt=0; var_cnt=0; arr_cnt=0; call_sp=0; for_sp=0; while_sp=0; data_count=0; on_error_line=-1;
        return;
    }

    /* CLEAR */
    if (strncasecmp(p,"CLEAR",5)==0&&!isalnum(p[5])) {
        var_cnt=0; arr_cnt=0; call_sp=0; for_sp=0; while_sp=0; data_pos=0; return;
    }

    /* MERGE */
    if (strncasecmp(p,"MERGE",5)==0&&!isalnum(p[5])) {
        p+=5; skip_ws(&p); char fname[MAXBUF]; str_expr(&p,fname);
        FILE *f=fopen(fname,"r"); if(!f)return;
        char line[MAXBUF]; while(fgets(line,MAXBUF,f)){
            line[strcspn(line,"\n")]=0; char *q=line; skip_ws(&q);
            if(isdigit(*q)){int num=(int)strtol(q,&q,10);skip_ws(&q);insert_line(num,q);}
        } fclose(f); return;
    }

    /* GET / PUT (file) */
    if (strncasecmp(p,"GET",3)==0&&!isalnum(p[3])) { p+=3; /* stub */ return; }
    if (strncasecmp(p,"PUT",3)==0&&!isalnum(p[3])) { p+=3; /* stub */ return; }

    /* FIELD */
    if (strncasecmp(p,"FIELD",5)==0&&!isalnum(p[5])) { return; /* stub */ }

    /* RESET */
    if (strncasecmp(p,"RESET",5)==0&&!isalnum(p[5])) { return; /* stub */ }

    printf("?Syntax error: %.40s\n",p);
}

/* Execute : separated stmts on a line */
void execute_line(char *text) {
    char buf[MAXBUF]; strncpy(buf,text,MAXBUF-1); buf[MAXBUF-1]=0;
    char *p=buf;
    while(*p && running!=0) {
        char stmt[MAXBUF]; int i=0;
        int in_q=0;
        while(*p){
            if(*p=='"') in_q=!in_q;
            if(*p==':' && !in_q){ p++; break; }
            stmt[i++]=*p++;
        }
        stmt[i]=0;
        int prev_running=running;
        execute_stmt(stmt);
        if(running==2) return; /* jump happened */
    }
}

void run_from(int idx) {
    running=1; cur_line_idx=idx;
    while(running==1 && cur_line_idx>=0 && cur_line_idx<prog_cnt){
        if(tron_flag) printf("[%d]",program[cur_line_idx].num);
        int save=cur_line_idx;
        execute_line(program[cur_line_idx].text);
        if(running==2){ running=1; }
        else if(running==1) cur_line_idx++;
    }
    running=0;
}

/* ============================================================
   MAIN - READY loop (asm READY/PROMPT)
   ============================================================ */
int main() {
    srand((unsigned)time(NULL));
    memset(file_handles,0,sizeof(file_handles));
    on_error_line=-1;
    printf("MS BASIC-80 C Port\nOk\n");
    char input[MAXBUF];
    while(1){
        printf("> ");
        fflush(stdout);
        if(!fgets(input,MAXBUF,stdin)) break;
        input[strcspn(input,"\n")]=0;
        if(!*input) continue;
        char *p=input; skip_ws(&p);
        if(isdigit(*p)){
            int num=(int)strtol(p,&p,10); skip_ws(&p);
            insert_line(num,*p?p:"");
        } else {
            execute_stmt(p);
        }
        if(!running) printf("Ok\n");
    }
    return 0;
}