Algorithm:-
begin
if a,e,I,o,u or A,E,I,O,U
then
printf “It is a vowel”
else
printf “It is a consonant”
end

1. LEX program to count number of vowels and consonants in a given input string

%%
{printf(“it is vowel”);}
{printf(“it is consonant”);}
%%
main()
{
yylex();
}
int yywrap()
{
return 1;
}


Output:

$./a.out
a
it is a vowel
g
it is a consonant
..............etc

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Objective
Program in “C/Lex” to check whether Identifier is valid or not
#include
#include
void main()
{
clrscr();
int i=0,j=0,flag=1;
char ch,ip;
while((ch=getchar())!='\n')
{
ip=ch;
i++;
}
ip='*';
if((ip>='a'&&ip<='z')||(ip>='A'&&ip<='Z'))
{
j++;
while(ip!='*')
{
if((ip>='a'&&ip<='z')||(ip>='A'&&ip<='Z')||(ip>='0'&&ip<='9')||ip=='_')
{
j++;
}
else
{
flag=0;
goto loop;
}
}
}
else
flag=0;
lo..............etc

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Objective
Program in “LEX” to count number of Characters, Words, Lines.

%{
int nchar=0,nword=0,nline=0;
#include
%}
%%
\n {nline++;nchar++;}
+ {nword++;nchar+=yyleng;}
. {nchar++;}
%%
int main()
{
yylex();
printf(%d%d%d,nchar,nword,nline);
}
..............etc

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Objective
Program in “LEX” to count number of vowels and consonants .

%{
int count1=0;
int count2=0;
%}
%%
aIeIiIoIu {printf(%s is vowel,yytext);count1++;}
{printf(%s is constonant,yytext);count2++;}
.I\n {ECHO;}
%%
main()
{
yylex();
printf(%d Vowel =%d constonant=,count1,count2);
}
..............etc

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Objective
Program in “LEX” to count the verb in a given line of text.

%{
%}
%%
isI
areI
amI printf(%s is verb,yytext );
+ {printf(%s is not a verb,yytext);}
.I\n {ECHO;}
%%
main()
{
yylex();
}
..............etc

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Objective
Program in “LEX” to count number of Identifiers and Keywords.

digit
letter
%{
int count1=0;
int count2=0;
%}
%%
intI
floatI
char {count++;printf(%s is keyword,yytext);}
{letter}I({letter}I{digit})*{count2++;}
+ {printf(%s is not keyword,yytext);}
.I\n {ECHO;}
%%
main()
{
yylex();
printf(%d no of keyword %d no of id,count1,count2);
}
..............etc

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lex program to recognise and count number of identifiers in a given file ?..............etc

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..............etc

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could you please send me the lex program to specify decimal numbers..............etc

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C++ Lex using CSharp is a system software ( Lexical Analyzer) project where the input program is broken down into many fragments called tokens. Basically lexical analysis involves scanning the program to be compiled and recognizing the tokens that make up the source statements. Scanners are usually designed to recognize keywords, operators, and identifiers, as well as integers, floating point numbers, character strings, and other similar items that are written as part of source program. The exact set of tokens to be recognized depends upon the ..............etc

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