07-05-2011, 12:49 PM
Objective
Program in “C/Lex” to check whether Identifier is valid or not
Code:
#include<stdio.h>
#include<conio.h>
void main()
{
clrscr();
int i=0,j=0,flag=1;
char ch,ip[100];
while((ch=getchar())!='\n')
{
ip[i]=ch;
i++;
}
ip[i]='*';
if((ip[j]>='a'&&ip[j]<='z')||(ip[j]>='A'&&ip[j]<='Z'))
{
j++;
while(ip[j]!='*')
{
if((ip[j]>='a'&&ip[j]<='z')||(ip[j]>='A'&&ip[j]<='Z')||(ip[j]>='0'&&ip[j]<='9')||ip[j]=='_')
{
j++;
}
else
{
flag=0;
goto loop;
}
}
}
else
flag=0;
loop:
if(flag==0)
printf("invalid");
else
printf("valid");
getch();
}