0917. Group Lexical analysis

#include <stdio.h>
#include <string.h>
Char input[200];//Store Input string
Char token[5];//holds the string that makes up the word symbol
Char ch; Holds the current read-in character
int p; Input[] Subscript
int FG; Switch tag
int num; Store shaping values

Two-dimensional character array, storing the keyword
Char index[6][6]={' begin ', ' if ', ' then ', ' while ', ' Do ', ' end '};
Main ()
{
P=0;
printf ("Intput string (End with ' # '): \ n");
Do
{
Ch=getchar ();
Input[p++]=ch;
}while (ch!= ' # ');
P=0;
Do
{
Scaner ();
Switch (FG)
{
Case 11:printf ("(%d,%d)", fg,num);
case-1:printf ("Input error\n"); Break
Default:printf ("(%d,%s)", Fg,token);
}
}while (fg!=0);
Getch (); For the program to stay on the display page
}
/* Lexical scanner: */
Scaner ()
{
int m=0;//token[] Subscript
int n;

Empty token[]
for (n=0;n<5;n++)
Token[n]=null;

Gets the first one that is not 0 characters
Ch=input[p++];
while (ch== ") ch=input[p++];

Keyword (identifier) processing process
if ((ch<= ' z ' &&ch>= ' a ') | | (ch<= ' Z ' &&ch>= ' A '))
{
while ((ch<= ' z ' &&ch>= ' a ') | | (ch<= ' Z ' &&ch>= ' A ') | | (ch<= ' 9 ' &&ch>= ' 0 '))
{
Token[m++]=ch;
Ch=input[p++];
}
token[m++]= ' + ';
CH=INPUT[--P];
fg=10;
for (n=0;n<6;n++)
if (strcmp (Token,index[n]) ==0)//strcmp () compares two strings, equals returns 0
{
fg=n+1;
Break
}
}

Digital processing Flow
else if ((ch<= ' 9 ' &&ch>= ' 0 '))
{
num=0;
while ((ch<= ' 9 ' &&ch>= ' 0 '))
{
num=num*10+ch-' 0 ';
Ch=input[p++];
}
CH=INPUT[--P];
fg=11;
}

Operator interface Processing Flow
Else
Switch (CH)
{
Case ' < ':
m=0;
Token[m++]=ch;
Ch=input[p++];
if (ch== ' > ')//Generate <>
{
fg=21;
Token[m++]=ch;
}
else if (ch== ' = ')//Generate <=
{
fg=22;
Token[m++]=ch;
}
Else
{
fg=20;
CH=INPUT[--P];
}
Break
Case ' > ':
Token[m++]=ch;
Ch=input[p++];
if (ch== ' = ')//Generate >=
{
fg=24;
Token[m++]=ch;
}
else//Generate >
{
fg=23;
CH=INPUT[--P];
}
Break
Case ': ':
Token[m++]=ch;
Ch=input[p++];
if (ch== ' = ')//generated: =
{
fg=18;
Token[m++]=ch;
}
else//Generate:
{
fg=17;
CH=INPUT[--P];
}
Break
Case ' + ': fg=13;token[0]=ch;break;
Case '-': fg=14;token[0]=ch;break;
Case ' * ': fg=15;token[0]=ch;break;
Case '/': fg=16;token[0]=ch;break;
Case ': = ': Fg=18;token[0]=ch;break;
Case ' <> ': fg=21;token[0]=ch;break;
Case ' <= ': fg=22;token[0]=ch;break;
Case ' >= ': fg=24;token[0]=ch;break;
Case ' = ': fg=25;token[0]=ch;break;
Case '; ': fg=26;token[0]=ch;break;
Case ' (': fg=27;token[0]=ch;break;
Case ') ': fg=28;token[0]=ch;break;
Case ' # ': fg=0;token[0]=ch;break;
Default:fg=-1;
}
}

0917. Group Lexical analysis