Recursive Descent Parser in C

rdparser.c

#include <stdio.h>
char input[100];
int i;
int T();
int F();
int TP();
int EP();

int E()
{
	if(T())
	{
		if(EP())
			return(1);
		else return(0);
	}
	else
		return(0);
}

int EP()
{
	if(input[i]=='+')
	{
		i++;
		if(T())
		{
			if(EP())
				return(1);
			else
				return(0);
		}
		else
			return(0);
	}
	else
		return(1);
}

int T()
{
	if(F())
	{
		if(TP())
			return(1);
		else
			return(0);
	}
	else
		return(0);
}

int TP()
{
	if(input[i]=='*')
	{
		i++;
		if(F())
		{
			if(TP())
				return(1);
			else
				return(0);
		}
		else
			return(0);
	}
	else
		return(1);
}

int F()
{
	if(input[i]=='(')
	{
		i++;
		if(E())
		{
			if(input[i]==')')
			{
				i++;
				return(1);
			}
			else
				return(0);
		}
		else
			return(0);
	}
	else
		if(input[i]>='a'&&input[i]<='z'||input[i]>='A'&&input[i]<='Z')
		{
			i++;
			return(1);
		}
		else
			return(0);
}

//Main Program
void main(){
  printf("Recursive Decent Parser\n");
  printf("E->TE'\nE'->TE'/@\nT->FT'\nT'->*FT'/@\nF->(E)/ID\n");
  gets(input);

  if (E()){
      if (input[i+1]=='\0'){
        printf("String is accepted\n");
      }
      else{
        printf("String is not accepted\n");
      }
  }
  else{
      printf("String is not accepted\n");
  }
}