Implementation of simple lexical analyzer

Compiling a compiled program for a simple subset of languages using C language in a single scan

#include <iostream> #include <string.h> #include <ctype.h> Char Prog[80],token[8]; Char ch; int syn,p,m,n,sum=0; Char *rwtab[6]={' begin ', ' if ', ' then ', ' while ', ' Do ', ' end '}; void Scanner () { m=0; for (n=0;n<8;n++) Token[n]=null; Ch=prog[p++]; while (ch== ") ch=prog[p++]; if (Isalpha (CH))//alphabetic character { while (isdigit (ch) | | Isalpha (CH))//alphabetic or numeric characters { Token[m++]=ch; Ch=prog[p++]; } Token[m++]= ' ";p--;syn=10; for (n=0;n<6;n++) if (strcmp (Token,rwtab[n]) ==0) { syn=n+1; Break } } else if (isdigit (CH))//numeric characters { sum=0; while (IsDigit (CH))//shuzi { sum=sum*10+ch-' 0 '; Ch=prog[p++]; } p--; syn=11; } Else Switch (CH) { Case ' < ': m=0; Token[m++]=ch; Ch=prog[p++]; if (ch== ' > ') { syn=22; Token[m++]=ch; } else if (ch== ' = ') { syn=22; Token[m++]=ch; } Else { syn=20; p--; } Break Case ' > ': token[m++]=ch; Ch=prog[p++]; if (ch== ' = ') { syn=24; Token[m++]=ch; } Else { syn=23; p--; } Break Case ': ': token[m++]=ch; Ch=prog[p++]; if (ch== ' = ') { syn=18; Token[m++]=ch; } Else { syn=17; p--; } Break Case ' + ': syn=13;token[0]=ch;break; Case '-': syn=14;token[0]=ch;break; Case ' * ': syn=15;token[0]=ch;break; Case '/': syn=16;token[0]=ch;break; Case ' = ': syn=25;token[0]=ch;break; Case '; ': syn=26;token[0]=ch;break; Case ' (': syn=27;token[0]=ch;break; Case ') ': syn=28;token[0]=ch;break; Case ' # ': syn=0;token[0]=ch;break; Default:syn=-1; } } void Main () { using namespace Std; P=0; int i; printf ("\ n Please input string:\n"); do{ Ch=getchar (); Prog[p++]=ch; }while (ch!= ' # '); P=0; do{ Scanner (); Switch (SYN) { Case 11:printf ("(%d,%d)", syn,sum); Break case-1:printf ("error!"); Break Default printf ("(%d,", SYN); For (I=0;i<strlen (token); i++) { printf ("%c", Token[i]); } printf (")"); } }while (syn!=0); }

Implementation of simple lexical analyzer