Silver Oak Group of Institutes
Silver Oak College of Engineering & Technology
Aditya Silver Oak Institute of Technology
GUJARAT TECHNOLOGICAL UNIVERSITY BACHELOR OF
ENGINEERING
COMPILER DESIGN
(3170701)
COMPUTER ENGINEERING / INFORMATION TECHNOLOGY
DEPARTMENT

ii
COMPILER DESIGN PRACTICAL BOOK DEPARTMENT
OF COMPUTER ENGINEERING PREFACE
It gives us immense pleasure to present the first edition of Compiler Design Practical Book for the
B. Tech. 4th year students for SILVER OAK GROUP OFINSTITUTES.
The Compiler Design theory and laboratory course at SILVER OAK GROUP OF INSTITUTES,
AHMEDABAD is designed in such a way that students develop the basic understanding of the
Compiler Design and various applications in the theory classes and then try their hands on the
experiments to realize the various aspects of Compiler Design.
This laboratory course is intended to make the students experiment on the basic techniques of
compiler construction and tools that can used to perform syntax-directed translation of a high-
level programming language into an executable code. Students will design and implement
language processors in C by using tools to automate parts of the implementation process. This
will provide deeper insights into the more advanced semantics aspects of programming
languages, code generation, machine independent optimizations, dynamic memory allocation,
and objectorientation
Hopefully this Compiler Design Practical Book will serve the purpose for which it has been
developed.
Lab Manual Revisedby:Prof.Monali Suthar, SilverOakCollege of EngineeringandTechnology
Prof. Jalpa Shah, Aditya Silver Oak Institute of Technology
Lab Manual Revision No.: SOGI_2170701_LM_2019_1

iii
INSTRUCTIONS TO STUDENTS
1. While entering into the LAB students should wear their ID cards and arrange your shoes in
properway.
2. All the students must come with the lab manual in every practicalsession.
3. Students have to maintain their lab manual on regular basis(it means evaluation of practical
will be doneweekly)
4. Questions given in the lab manual must be attempted and solved on the givendate.
5. Feedback and conclusion section of each practical must be filled with utmostsincerity.
6. Lab manual must be filled only after performing thepractical.
7. Students should maintain decorum inside thelaboratory.
8. All the observations have to be neatly recorded in the Practical Class Notebook and verified
by the instructor before leaving thelaboratory.
9. Write the answers of all the questions at the end of each experiment in the PracticalBook.
10. Lab Manual records need to be submitted on or before date ofsubmission.
11. The grades for the Practical course work will be awarded based on your performance in the
laboratory, regularity, obtaining of experiments results, labquiz, regular viva-voice and end-term
examination.
12. Students are restricted to not to use mobile phones inside thelaboratory.
13. After completing the laboratory exercise make sure to shut down the systemand switch off
all the amities properly. Also rearrange the chair in the properway.

iv
CERTIFICATE
This is to certify that
Mr. Dhaval r tukadiya withenrolmentno.180770107240, Semester 7
DIV-D has successfully completed his laboratory experiments in the Compiler
Design (2170701) from the department of Computer Engineering during the
academic year ...2020............ -..2021.....
Date ofSubmission:..5-10-2020....................... Staff in charge:...........................
Head of Department: ...........................................

v
TABLE OF CONTENT
Sr.
No Experiment Title
Page No
Date of
Start
Date of
Completion Sign
Marks
(out of
10)
From To
1
To study the various types of
errors in compiler.
1 4
2
Study of Lex/Yacc of
Compiler Writing.
5 8
3
Write a Program to check
whether a string belongs to
grammar or not.
9 13
4
Write a Program to check
whether a string belongs to
grammar or not.
14 18
5
Write a program to compute
FIRST of non-terminals
19 24
6
Write a program to check
whether a string is keyword
and constant.
25 28

vi
7
Write a program to count
number of new lines and
white spaces.
29 30
8
Write a program to count the
number of vowels and
consonants in a given string.
31 33
9
Write a program to count
number of characters, words,
spaces, end of lines in a given
input file.
34 37

vi
10
Write a program to recognize
whether a given sentence is
simple 30/9/14 or compound.
38 40
11
Write a program to test the
validity of a simple
expression involving
operators +, -,* and /.
41 43
12
nested IF control statements
and display the levels of
nesting.
44 47
13
strings ‘aaab’, ‘abbb’, ‘ab’, and
‘a’ using grammar.
48 51

1
PRACTICAL SET-1
Types of program errors
We distinguish between the following types of errors:
1. Syntax errors: errors due to the fact that the syntax of the language is notrespected.
2. Semantic errors: errors due to an improper use of programstatements.
3. Logical errors: errors due to the fact that the specification is notrespected.
From the point of view of when errors are detected, we distinguish:
1. Compile time errors: syntax errors and static semantic errors indicated by thecompiler.
2. Runtime errors: dynamic semantic errors, and logical errors, that cannot be detected
by the compiler(debugging).

2
AIM: To study the various types of errors in compiler.
// C program to illustrate
// syntax error
#include<stdio.h>
void main()
{
int x = 10;
int y = 15;
printf("%d", (x, y)) // semicolon missed
}
Error:
error: expected ';' before '}' token
Syntax of a basic construct is written wrong. For example : while loop
// syntax error
#include<stdio.h>
int main(void)
{
// while() cannot contain "." as an argument.
while(.)
{
printf("hello");
}
return 0;

3
}
Error:
error: expected expression before '.' token
while(.)
In the given example, the syntax of while loop is incorrect. This causes a syntax error.
Run-time Errors: Errors which occur during program execution(run-time) after successful compilation are called
run-time errors. One of the most common run-time error is division by zero also known as Division error. These
types of error are hard to find as the compiler doesn’t point to the line at which the error occurs. For more
understanding run the example given below.
// run-time error
#include<stdio.h>
void main()
{
int n = 9, div = 0;
// wrong logic
// number is divided by 0,
// so this program abnormally terminates
div = n/0;
printf("resut = %d", div);
}
Error:
warning: division by zero [-Wdiv-by-zero]
div = n/0;

4
In the given example, there is Division by zero error. This is an example of run-time error i.e errors occurring while
running the program.
Linker Errors: These error occurs when after compilation we link the different object files with main’s object
using Ctrl+F9 key(RUN). These are errors generated when the executable of the program cannot be generated. This
may be due to wrong function prototyping, incorrect header files. One of the most common linker error is writing
Main() instead of main().
// linker error
#include<stdio.h>
void Main() // Here Main() should be main()
{
int a = 10;
printf("%d", a);
}
Error:
(.text+0x20): undefined reference to `main'
Logical Errors : On compilation and execution of a program, desired output is not obtained when certain input
values are given. These types of errors which provide incorrect output but appears to be error free are called logical
errors. These are one of the most common errors done by beginners of programming. These errors solely depend on
the logical thinking of the programmer and are easy to detect if we follow the line of execution and determine why
the program takes that path of execution.
// logical error

5
int main()
{
int i = 0;
// logical error : a semicolon after loop
for(i = 0; i < 3; i++);
{
printf("loop ");
continue;
}
getchar();
return 0;
}
No output
Semantic errors: This error occurs when the statements written in the program are not meaningful to the compiler.
// semantic error
void main()
{
int a, b, c;
a + b = c; //semantic error
}
Error
Error: lvalue required as left operand of assignment
a + b = c; //semantic error

6
Question Answers:
1. Consider the following C declaration. int x[10], y,z; What kind of error does following
statement contain? z == x+y;
a. Syntaxerror
b. Semantic error
c. Logicalerror
d. All of theabove
2. Write down types of errorsgenerated.
Logical error
Semantic error
Syntax error
3. All syntax errors and some of the semantic errors (the static semantic errors) are
detected bythe Compiler.
4. Errors that occur when you violate the rules of writing C/C++ syntax are knownas
Syntax error .

7
5. Error is an illegal operation performed by the user which results in abnormal working of
the program. State TRUE orFALSE.
TRUE

8
PRACTICAL SET-2
Lex/Yacc compiler
A compiler or interpreter for a programming language is often decomposed into two parts:
1. Read the source program and discover itsstructure.
2. Process this structure, e.g. to generate the target program.
Lex and Yacc can generate program fragments that solve the first task.
The task of discovering the source structure again is decomposed into subtasks:
1. Split the source file intotokens(Lex).
2. Find the hierarchical structure of the program(Yacc).

9
AIM: Study of Lex/Yacc of Compiler Writing.
A compiler or interpreter for a programming language is often decomposed into two parts:
1. Read the source program and discover its structure.
2. Process this structure, e.g. to generate the target program.
Lex and Yacc can generate program fragments that solve the first task.
The task of discovering the source structure again is decomposed into subtasks:
1. Split the source file into tokens (Lex).
2. Find the hierarchical structure of the program (Yacc).
Description:
Some of the most time consuming and tedious parts of writing a compiler involve the lexical scanning and syntax
analysis. Luckily there is freely available software to assist in these functions. While they will not do everything for
you, they will enable faster implementation of the basic functions. Lex and Yacc are the most commonly used
packages with Lex managing the token recognition and Yacc handling the syntax. They work well together, but
conceivably can be used individually as well.
Both operate in a similar manner in which instructions for token recognition or grammar are written in a special file
format. The text files are then read by lex and/or yacc to produce c code. This resulting source code is compiled to
make the final application. In practice the lexical instruction file has a “.l” suffix and the grammar file has a “.y”
suffix. This process is shown in Figure 1.
Figure 1.Lex and Yacc Process (based on a diagram on page 5 of “A Compact Guide to Lex & Yacc” by Thomas
Niemann)
The file format for a lex file consists of (4) basic sections
• The first is an area for c code that will be place verbatim at the beginning of the generated source code. Typically
is will be used for things like #include, #defines, and variable declarations.
• The next section is for definitions of token types to be recognized. These are not mandatory, but in general makes
the next section easier to read and shorter.
• The third section set the pattern for each token that is to be recognized, and can also include c code to be called
when that token is identified

10
• The last section is for more c code (generally subroutines) that will be appended to the end of the generated c
code. This would typically include a main function if lex is to be used by itself.
• The format is applied as follows (the use and placement of the % symbols are necessary):
%
{
//header c code
%}
//definitions
%%
//rules
%%
//subroutines
The format for a yacc file is similar, but includes a few extras.
• The first area (preceded by a %token) is a list of terminal symbols. You do not need to list single character ASCII
symbols, but anything else including multiple ASCII symbols need to be in this list (i.e. “==”).
• The next is an area for c code that will be place verbatim at the beginning of the generated source code.Typically
is will be used for things like #include, #defines, and variable declarations.
• The next section is for definitions - none of the following examples utilize this area • The fourth section set the
pattern for each token that is to be recognized, and can also include c code to be called when that token is identified
• The last section is for more c code (generally subroutines) that will be appended to the end of the generated c
code. This would typically include a main function if lex is to be used by itself.
• The format is applied as follows (the use and placement of the % symbols are necessary):
%tokens RESERVED, WORDS, GO, HERE
%{
//header c code
%}
//definitions
%%

11
//rules
%%
//subroutines
These formats and general usage will be covered in greater detail in the following (4) sections. In general it is best
not to modify the resulting c code as it is overwritten each time lex or yacc is run. Most desired functionality can be
handled within the lexical and grammar files, but there are some things that are difficult to achieve that may require
editing of the c file.

12
Question Answers:
1. YACC is a computerprogramfor
operationsystem
.
b. DOS
c. Unix
d.
d. openSUSE
2. Input of Lexis
a. Set to regular
expression
b. Statement
c. Numeric data
d. ASCII data
3. Which of the following software tool is parser
generator? a.Lex
b. Yacc
c. Both of the
mentioned
d. None of
thementioned
a.Windows

13
4.
5. Yacc semantic action is a sequence of C Program State TRUE or FALSE.
TRUE
The YACC takes C code as inputandoutputsfile whoch contain souce code that can be combined
into actual parser. .

14
PRACTICAL SET-3
Grammar
Definition − A context-free grammar (CFG) consisting of a finite set of grammar rules is a
quadruple (N, T, P, S) where
N is a set of non-terminalsymbols.
 T is a set of terminals where N ∩ T =NULL.
 P is a set of rules, P: N → (N ∪T)*, i.e., the left-hand side of the production rule P does
have any right context or leftcontext.
S is the startsymbol.
Example
 The grammar ({A}, {a, b, c}, P, A), P : A → aA, A→abc.
 The grammar ({S, a, b}, {a, b}, P, S), P: S → aSa, S → bSb, S→ε
 The grammar ({S, F}, {0, 1}, P, S), P: S → 00S | 11F, F → 00F|ε
The set of all strings that can be derived from a grammar is said to be the language generated
from that grammar. A language generated by a grammar G is a subset formally definedby
 L(G)={W|W ∈ ∑*, S ⇒GW}
If L(G1) = L(G2), the Grammar G1 is equivalent to the Grammar
G2.Example
If there is a grammar
G: N = {S, A, B} T = {a, b} P = {S → AB, A → a, B → b}

15
Here S produces AB, and we can replace A by a, and B by b. Here, the only accepted
string is ab, i.e.,
L(G) = {ab}
Example
Suppose we have the following grammar −
G: N = {S, A, B} T = {a, b} P = {S → AB, A → aA|a, B → bB|b}
The language generated by this grammar −
L(G) = {ab, a2b, ab2, a2b2, ………}
= {am bn | m ≥ 1 and n ≥ 1}

16
AIM: Write a Program to check whether a string belongs to grammar ornot.
Code:
#include<stdio.h>
#include<conio.h>
#include<string.h>
void main() {
char string[50];
int flag,count=o;
clrscr();
printf("The grammar is: S->aS, S->Sb, S->abn");
printf("Enter the string to be checked:n");
gets(string);
if(string[0]=='a') {
flag=0;
for (count=1;string[count-1]!='0';count++) {
if(string[count]=='b') {
flag=1;
continue;
} else if((flag==1)&&(string[count]=='a')) {
printf("The string does not belong to the specified grammar");
break;
} else if(string[count]=='a')
continue; else if(flag==1)&&(string[count]='0')) {
printf("String accepted…..!!!!");
break;
} else {
printf("String not accepted");
}
}
}
getch();
}

17
Output:
The grammar is
s-> as
s->sb
s->ab
Enter the string to be checked: aab
String accecpted…!!!

18
Question Answers:
1. Which of the following statement isfalse?
a. Context free language is the subset of context sensitive
language b. Regular language is the subset of context
sensitivelanguage
c. Recursively ennumerable language is the super set of regular language
d. Context sensitive language is a subset of context free language
2. The minimum number of productions required to produce a language
consistingof palindrome strings over ∑={a,b}is
a. 3
b. 7
c. 5
d. 6
3. Find a regular expression for a grammar which generates a language which states:
L contains a set of strings starting wth an a and ending with a b, with something in
the middle.
a. a(a*Ub*)
bb.
a*(aUb)b*
c.a(a*b*)b
d. None of the mentioned

19
4. Which of the following is the correct representation of grammar for the given
regular expression?a(aUb)*b
a. S →aMb
M → e
M → aM
M →bM
b. (1) S →aMb
(2) M →Mab
(3) M →aM
(4) M → bM
c. (1) S →aMb
(2) M →e
(3) M →aMb
(4) M → bMa
d. None of thementioned
5. Define of Context freeGrammar.
Context-free grammars(CFGs) are usedtodescribe context-free languages.A context-freegrammarisa setofrecursive
rulesusedtogenerate patterns of strings ....CFG's are usedto describe programminglanguagesandparserprograms in
compilerscanbe generatedautomaticallyfromcontext-free grammars.

20
PRACTICAL SET-4
Parse Tree:
A parse tree is an entity which represents the structure of the derivation of aterminal string from
some non-terminal (not necessarily the start symbol). The definition is as in the book. Key
features to define are the root ∈ V and yield ∈Σ* of each tree.
 For each σ ∈Σ, there is a tree with root σ and no children; its yield isσ
 For each rule A → ε, there is a tree with root A and one child ε; its yieldisε
 If t1, t2, ..., tn are parse trees with roots r1, r2, ..., rn and respective yields y1, y2, ..., yn, and
A → r1r2...rn is a production, then there is a parse tree with root A whose children are t1,
t2, ..., tn. Its root is A and its yield isy1y2...yn
Observe that parse trees are constructed from bottom up, not top down. The actual
construction of "adding children" should be made more precise, but we intuitively know what's
going on.
As an example, here are all the parse (sub) trees used to build the parse tree for the arithmetic
expression 4 + 3 * 2 using the expression grammar
E → E + T | E - T | T
T → T * F | F
F → a | ( E )
where a represents an operand of some type, be it a number or variable. The trees are grouped by
height.
The following code is supposed to generate a parse tree of the input expression, but the
problem is that the output E, T, F, S (functions used in the code).

21
AIM: Write a Program to generate a parse tree.
Code:
#include <stdio.h>
#include <stdlib.h>
#include <ctype.h>
char next;
void E(void);void T(void);
void S(void);void F(void);
void error(int);void scan(void);
void enter(char);
void leave(char);
void spaces(int);
int level = 0;
//The main should always be very simple
//First scan the string
//second checkfor end of string reached , if yes success and if not error.
//P ---> E '#'
int main(void){
printf("Input:");
scan(); E();
if (next != '#') error(1);
else printf("***** Successful parse *****n");
}

22
//E ---> T {('+'|'-') T}
void E(void){
enter('E');
T();
while (next == '+' || next == '-') {
scan();
T();
}
leave('E');
}
//T ---> S {('*'|'/') S}
void T(void)
{
enter('T'); S();
while (next == '*' || next == '/') {
scan(); S();
}
leave('T');
}
//S ---> F '^' S | F
void S(void)
{
enter('S'); F();
if (next == '^') {
scan(); S();
}
leave('S');}

23
//F ---> char | '(' E ')'
void F(void)
{
enter('F');
if (isalpha(next))
{
scan();
}
else if (next == '(') {
scan(); E();
if (next == ')')
scan();
else
error(2);
}
else {
error(3);
}
leave('F');
}
//Scan the entire input
void scan(void){
while (isspace(next = getchar()));
}
void error(int n)

24
{
printf("n*** ERROR: %in", n);
exit(1);
}
void enter(char name)
{
spaces(level++);
printf("+-%cn", name);
}
void leave(char name)
{
spaces(--level);
printf("+-%cn", name);
}
//TO display the parse tree
void spaces(int local_level)
{
while (local_level-- > 0)
printf("| ");
}

25
Question Answers:
1. Which among the following is the root of the parse
tree? a. Production P
b. Terminal T
c. Variable V
d. Starting Variable S
2. A grammar with more than one parse tree is
called: a.Unambiguous
b. Ambiguous
c. Regular
d. None of the mentioned
3. Directed Acyclic graphs is the acyclic graphical representation of agrammar.
4. Grammar is ambiguous if
a. it has 2 parsetrees
b. it has two left mostderivations
c. it has two right most
derivations d. All of theabove
5. Draw parse tree from given grammar for 3*2+5string.
E -> I
E -> E + EE
-> E * EE->
(E)
I -> ε | 0 | 1 | … | 9

26
PRACTICAL SET-5
First of NonTerminals
The rules for finding FIRST of a given grammar is: If
X is terminal, FIRST(X) = {X}.
If X → ε is a production, then add ε to FIRST(X).
If X is a non-terminal, and X → Y1 Y2 … Yk is a production, and ε is in all of FIRST(Y1), …,
FIRST(Yk), then add ε to FIRST(X).
If X is a non-terminal, and X → Y1 Y2 … Yk is a production, then add a to FIRST(X) if for
some i, a is in FIRST(Yi), and ε is in all of FIRST(Y1), …, FIRST(Yi-1).
Assumptions:
Each Non-terminal character is represented by one Uppercase letter.
Each Terminal character is represented by one lowercase letter.
LHS and RHS of each production will be separated by a "=" symbol.
There will be no Blank space within a production string.
Assumed that Left recursion is avoided in all input productions.

27
AIM: Write a program to compute FIRST of non-terminals
Code:
#include<stdio.h>
#include<conio.h>
char array[10][20],temp[10];
int c,n;
void fun(int,int[]);
int fun2(int i,int j,int p[],int );
void main()
{
int p[2],i,j;
printf("Enter the no. of productions :");
scanf("%d",&n);
printf("Enter the productions :n");
for(i=0;i<n;i++)
scanf("%s",array[i]);

28
for(i=0;i<n;i++)
{
c=-1,p[0]=-1,p[1]=-1;
fun(i,p);
printf("First(%c) : [ ",array[i][0]);
for(j=0;j<=c;j++)
printf("%c,",temp[j]);
printf("b ].n");
getch();
}
}
int fun2(int i,int j,int p[],int key)
{
int k;
if(!key)
{
for(k=0;k<n;k++)
if(array[i][j]==array[k][0])
break;

29
p[0]=i;p[1]=j+1;
fun(k,p);
return 0;
}
else
{
for(k=0;k<=c;k++)
{
if(array[i][j]==temp[k])
break;
}
if(k>c)return 1;
else return 0;
}
}
void fun(int i,int p[])
{
int j,k,key;
for(j=2;array[i][j] != NULL; j++)

39
{
if(array[i][j-1]=='/')
{
if(array[i][j]>= 'A' && array[i][j]<='Z')
{
key=0;
fun2(i,j,p,key);
}
else
{
key = 1;
if(fun2(i,j,p,key))
temp[++c] = array[i][j];
if(array[i][j]== '@'&& p[0]!=-1) //taking '@' as null symbol
{
if(array[p[0]][p[1]]>='A' && array[p[0]][p[1]] <='Z')
{
key=0;
fun2(p[0],p[1],p,key);

31
Output:
}
else
if(array[p[0]][p[1]] != '/'&& array[p[0]][p[1]]!=NULL)
{
if(fun2(p[0],p[1],p,key))
temp[++c]=array[p[0]][p[1]];
}
}
}
}
}
}

32
Question Answers:
1. What is terminal in grammar? How can you identify it in thegivengrammar?
A terminal is a symbol which does not appear on the left-hand side of any production.
A grammar contains a set of terminal symbols (tokens) such as the plus sign, +, the times sign, *,
and other tokens defined by the lexical analyzer such as Identifiers.
Eg: E- E+T
E- a
T - b
Here a,b,+ are terminals.
2. What is non-terminal in grammar? How can you identify it in the givengrammar?
Explain withexample.
Non-terminals are syntactic variables that denote sets of strings. The non-
terminals define sets of strings that help define the language generated by
the grammar. A set of tokens, known as terminal symbols (Σ). Terminals are the
basic symbols from which strings are formed
Eg: E- E+T
E- a
T - b
Here E,T are non terminals
3. If you find NULL or ε in the grammar then whatwill be the procedure forfindingtheFIRST?
It will be directlyincludedinfirsttable

33
4. Find the FIRST of the givengrammar.
S ->cAd
A -> bc|a
S: c
A: a,b
5. Find FIRST of the givengrammar
S→ABa /bCA
A→cBCD / є
B→CdA / ad
C→eC / є
D→bsf / a
Ans:
First of s: b,c,e
First of A: c, Ƹ
First of B: a,e,Ƹ
First of C: e ,Ƹ
First of D : a,b

34
PRACTICAL SET-6
Constants in C
As the name suggests the name constants is given to such variables or values in C programming
language which cannot be modified once they are defined. They are fixed values in a program.
There can be any types of constants like integer, float, octal, hexadecimal, character constants
etc. Every constant has some range. The integers that are too big to fit into an int willbe taken as
a long. Now there are various ranges that differ from unsigned to signed bits. Under signed bit
the range of an int, varies from -128 to +127 and under unsigned bit int varies from 0to255.
How to define constants?
In C program we can define constants in two ways as shown below:
1. using #define preprocessordirective
2. Using a constkeyword.
Keywords in C
Keywords are specific reserved words in C each of which has a specific feature associated with
it. Almost all of the words which help us use the functionality of the C language are included in
the list of keywords. So you can imagine that the list of keywords is not going to be a small one!
There are a total of 32 keywords in C:
auto, break, case, char, const, continue, default , do, double, else, enum, extern , float , for,
goto, if, int , long , register ,return ,short, signed, sizeof, static , struct ,switch, typedef ,union
,unsigned , void, volatile , while

35
AIM : Write a program to check whether a string is keyword and constant. Code:
#include <stdio.h>
#include <string.h>
int main() {
char keyword[32][10]={
"auto","double","int","struct","break","else","long",
"switch","case","enum","register","typedef","char",
"extern","return","union","const","float","short",
"unsigned","continue","for","signed","void","default",
"goto","sizeof","voltile","do","if","static","while"
} ;
char str[]="which";
int flag=0,i;
for(i = 0; i < 32; i++) {
if(strcmp(str,keyword[i])==0) {
flag=1;
}
}
if(flag==1)
printf("%s is a keyword",str);
else
printf("%s is not a keyword",str);
}
Output:
Which is not a keyword

36
Question Answers:
1. Use of “struct”keyword.
struct is used to declare a new data-type. Basically this means grouping variables together. For
example, a struct data type could be used to declare the format of the file.
2. Which keyword is used for define decimalvalues?
Float is used.
3. Why we need constant in C? Explain withexample.
Constants refer to fixed values that the program may not alter during its execution. These fixed values
are also called literals. Constants can be of any of the basic data types like an integer constant, a
floating constant, a character constant, or a string literal. There are enumeration constants as well.
4. Use of “sizeof” keyword.
The sizeof operator is the most common operator in C. It is a compile-time unary operator and used tocompute
the size of its operand. It returns the size of a variable......When sizeof() is used with the data types, it simply
returns the amount of memory allocated to that data type.
5. Which one of the following is not a reserved keyword for C?
a.Auto
b.Case
c.Main
d.default

37
PRACTICAL SET-7
Lexical Analysis
Lexical analysis is the first phase of a compiler. It takes the modified source code from language
preprocessors that are written in the form of sentences. The lexical analyzer breaks these
syntaxes into a series of tokens, by removing any whitespace or comments in the sourcecode.
AIM: Write a program to count number of new lines and white spaces.
Code:
#include<stdio.h>
#include<stdlib.h>
void main()
{
FILE *fp;
char ch;
int character = 0, space = 0, tab = 0, line = 0;
fp = fopen("/home/tusharsoni/Desktop/TestFile","r");
if(fp == NULL)
{
printf("File Not Foundn");
exit(1);
}
else
{
while(1)
{
ch = fgetc(fp);
if(ch == EOF)
{
break;
}
character++;
if(ch == ' ')
space++;
else if(ch == 't')
tab++;
else if(ch == 'n')
line++;
}

38
}
fclose(fp);
printf("nNumber of Characters = %dn", character);
printf("nNumber of Tabs = %dn", tab);
printf("nNumber of New Lines = %dn", line);
printf("nNumber of Spaces = %dn", space);
Output:

39
Question Answers:
1. The number of tokens in the following C statement is printf("i = %d, &i = %x", i,&i);
a.3 b.26 c.10 d.21
2. The output of a lexical analyzeris
a. A parsetree
b. Intermediate code
c. Machine code
d. A stream ofTokens
3. The number of tokens infollowing
program? # define M100
int main ( )
{
//
declarevariables
int n = 2020;
return n %M;
}
Answer:16
4. Number of tokens in the
statement: printf(“i=%d,&i=%x”,i,&bi);
Answer:
Printf(“i=%d,&i=%x”,I,&,I,);

40
5. Count the number of
tokens; voidmain()
{
i/* nt */a=10;
return;
}
Answer:13

42
PRACTICAL-8
lex
Lexis a programdesigned to generate scanners,also known as tokenizers, which recognize lexical
patterns in text. Lex is an acronym that stands for "lexical analyzer generator." It is intended
primarily for Unix-based systems. The code for Lex was originally developed by Eric Schmidt and
Mike Lesk.
FOR COMPILE AND EXECUTE:
lex file.l
gcc lex.yy.c -ly -ll
./a.out
AIM: Write a program to count the numberof vowels and consonants in a givenstring.
Code:
%{
int vow_count=0;
int const_count =0;
%}
%%
[aeiouAEIOU] {vow_count++;}
[a-zA-Z] {const_count++;}
%%
main()

43
{
printf("Enter the string of vowels and consonents:");
yylex();
printf("The number of vowels are: %dn",vow);
printf("The number of consonants are: %dn",cons);
return 0;
}
Output:
Enter the string of vowels and consonents
My name is Hina
The number of vowels are: 5
The number of consonants are: 7

44
Question Answers:
1. Which of the following is not a feature ofcompiler?
a. Scans the entire program first and then translate it into machinecode
b. When all the syntax errors are removed execution takesplace
c. Slow fordebugging
d. Execution time ismore
2. Input of Lexis?
a. Set to regularexpression
b. Statement
c. Numeric data
d. ASCIIdata
3. A Lex compilergenerates?
a. Lex objectcode
b. b.Transitiontables
c. CTokens
d. None ofabove

45
4. Analysis which determines the meaning of a statement onceitsgrammatical
e becomes known is termedas
a. Semantic analysis
b. Syntaxanalysis
c. Regularanalysis
d. Generalanalysis
structur

46
PRACTICAL SET-9
How to count Word,Character?
public int GetNumOfCharsInFile(string filePath)
{
int count = 0;
using (var sr = new StreamReader(filePath))
{
while (sr.Read() != -1)
count++;
}
return count;
}
FOR COMPILE AND EXECUTE:
lex file.l
./a.out

47
AIM: Write a program to count number of characters, words, spaces, end of lines in a given
input file.
Code:
%{
int ch=0,wd=0,l=0,sp=0;
%}
%%
(" ") {sp++;}
[n] {l++;}
[^ t n]+ {wd++; ch=ch+yyleng;}
%%
main()
{
yyin=fopen("kit.txt","r");
yylex();
printf("char=%d t words=%d t spaces=%d t lines=%d",ch,wd,sp,l);
}
Output:
(Content in file)
I love program ming.
Working with files in C program ming is fun.
I am learning C program ming at Codeforwin.
(Output)
Total characters = 106
Total words = 18
Total lines = 3

48
Question Answers:
1. Inacompiler checks every character of the sourcetext.
a. The lexicalanalyzer
b. The syntaxanalyzer
c. The codegenerator
d. The codeoptimizer
2. How many tokens are there in the following Cstatement?
a. printf (“j=%d, &j=%x”,j&j)
b. 4
c. 5
d. 9
e. 10
3. In a compiler, when is the keyboards of a language arerecognized?
a. During the lexical analysis of aprogram
b. During parsing of theprogram
c. During the codegeneration
d. During the data flowanalysis
4. The lexical analysis forJavaneeds _ in a necessary and sufficientsense.
a. Turingmachine
b. Non-deterministic push downautomata
c. Deterministic push downautomata
d. Finite stateautomata

49
PRACTICAL SET-10
For Compile And Execute:
lex file.l
./a.out
AIM: Write a program to recognize whether a given sentence is simple orcompound.
Code:
%{
int flag=0;
%}
%%
(""[aA][nN][dD]"")|(""[oO][rR]"")|(""[bB][uU][tT]"") {flag=1;}
%%
int main()
{
printf("Enter the sentencen");
yylex();
if(flag==1)
printf("nCompound sentencen");
else
printf("nSimple sentencen");
return 0;
}

50
Output:
$./a.out
Enter the sentence
I am Pooja
I am Pooja
[Ctrl-d]
Simple sentence
$./a.out
Enter the sentence
CSE or ISE
CSE or ISE
[Ctrl-d]
Compound sentence

51
Question Answers:
1. is not an advantage of using shared; dynamically linked libraries as
opposed to using statically linkedlibraries.
a. Lesser overall page fault rate inthesystem
b. Faster programstartup
c. Existing programs need not be relinked to take advantage of newerversions
d. Smaller sizes of executablefiles
2. The number of derivation trees for the correct answer strings to question 30is
a. 4
b. 1
c. 3
d. 2
3. Assuming that the input is scanned in left to right order, while parsing an input string
the top-down parseruse
a. Rightmostderivation
b. Leftmostderivation
c. Rightmost derivation that is traced out inreverse
d. Leftmost derivation that is traced out inreverse
4. is atop-downparser
a. Operator precedenceparser
b. An LALR (k)parser
c. An LR (k)parser
d. Recursive descentparser

52
PRACTICAL SET-11
YACC:
YACC program also consists of three sections, "Definitions", "Context Free Grammar and action
for each production","Subroutines/Functions".
In first section, we can mention C language code which may consist of header files inclusion,
globalvariables/Constants definition/declaration. C languagecode can bementioned inbetween
the symbols %{ and %}. Alsowe can define tokens in the first section. In above program, NUMBER
is the token. We can define the associativity of the operations (i.e. left associativity or right
associativity). In above yacc program, we have specified left associativity for all operators.
Priorities among the operators can also be specified. It is in the increasing order "from top to
bottom". For e.g. in our above yaccprogram, round brackets '(',')' has the higherpriority than '*',
'/', '%' which has higher priority than '+', '-'. Operators in the same statement have the same
priority. For e.g. in our above program all of the '*', '/', '%' have the samepriority.
In second section, we mention the grammar productions and the action for each production.
$$ refer to the top of the stack position while $1 for the first value, $2 for the second value
in the stack.
Third section consists ofthe subroutines. We have to call yyparse() to initiatethe parsing process.
yyerror() function is called when all productions in the grammar in second section do not match
to the inputstatement.
For compile and execute:-
yacc -d y2.y
lex y2.l
cc lex.yy.c y.tab.c -ll
./a.out

53
AIM: Write a program to test the validity of a simple expression involving operators +, -,*
and /.
Code:
%{
#include<stdio.h>
#include<stdlib.h>
%}
%token NUMBER ID NL
%left '+' '-'
%left '*' '/'
%%
stmt: exp NL {printf("valid expressionn"); exit(0);}
;
exp: exp '+' exp | exp '-' exp | exp '*' exp | exp '/' exp | '(' exp ')' | ID | NUMBER
;
%%
int yyerror(char *msg)
{
printf("Invalid expressionn");
exit(0);
}

54
main()
{
printf("enter the expression: n");
yyparse();
}
LEX PART:
CODE:(sarith.l)
%{
#include"y.tab.h"
%}
%%
[0-9]+ {return NUMBER;}
[a-zA-Z][a-zA-Z0-9_]* {return ID;}
n {return NL;}
. {return yytext[0];}
%%

55
Output:
yacc -d sarith.y
lex sarith.l
cc y.tab.clex.yy.c-ly-ll
./a.out
enterthe expression:
a+10
validexpression
yacc -d sarith.y
lex sarith.l
./a.out
enterthe expression:
10-
Invalidexpression

56
Questions Answers:
1.
a. Windows
b. DOS
c. Unix
d. OpenSUSE
2. The table is created byYACC.
a. LALRparsing
b. LLparsing
c. GLRparsing
3. The YACC takes C code as input andoutputs
a. Top downparsers
b. Bottom upparsers
c. Machine code
4. Input of Lex is?
a. Set of regularexpression
b. Statement
c. Numeric data
YACC is a computerprogramfor operationsystem.

57
PRACTICAL SET-12
Nested if :
Syntax:
if (condition1){ Statement1; }
else_if(condition2)
{ Statement2; }
else Statement 3;Description:
If condition 1 is false, then condition 2 is checked and statements are
executed if it is true. If condition 2 also gets failure, then else part is executed.
AIM: Write a program to recognize nested IF control statements and display
the levels of nesting.
Code:
LEX CODE
%option noyywrap
%{
#include "y.tab.h"
%}
%%
"if" {return IF;}
[sS][0-9]* {return S;}
"<"|">"|"=="|"<="|">="|"!=" {return RELOP;}
[0-9]+ {return NUMBER;}
[a-z][a-zA-Z0-9_]* {return ID;}
n {return NL;}
. {return yytext[0];}
%%

58
YACC CODE
%{
#include<stdio.h>
#include<stdlib.h>
int count=0;
%}
%token IF RELOP S NUMBER ID NL
%%
stmt: if_stmt NL {printf("No. of nested if statements=%dn",count);exit(0);}
;
if_stmt : IF'('cond')''{'if_stmt'}' {count++;}
|S
;
cond: x RELOP x
;
x:ID | NUMBER
;
%%
int yyerror(char *msg)
{
printf("the statement is invalidn");
exit(0);
}
main()
{
printf("enter the statementn");
yyparse();
}

59
Output:
yacc -d nif.y
lex nif.l
./a.out
enterthe statement
if(a<b){s}
No.of nestedif statements=1
./a.out
enterthe statement
if(a>b){if(a>b){s}}
No.of nestedif statements=2

60
Question Answers:
1. What will be the output of following program?
#include<stdio.h>i
ntmain()
{
int a=10;
if(a==10)
{
printf("Hello...");
break;
printf("Ok");
}
else
{
}
printf("Hii");

61
return 0;
}
a. Hello...
b. Hello...OK
c. OK
d. Error
2. What will be the output of following program
? #include <stdio.h>
int main()
{
if( (-100 && 100)||(20 && -20) )
printf("%s","Condition is true.");
else
printf("%s","Condition is false.");
return 0;
}
a. Condition istrue.
b. Condition isfalse.
c. No output
d. ERROR

62
3. Comment on the following codebelow
#include <stdio.h>
void main(){
int x = 5;
if (true);
printf("hello");
}
a. It will displayhello
b. It will throw anerror
c. Nothing will bedisplayed
d. Compilerdependent
4. The output of the code below
is #include<stdio.h>
void main()
{
int x = 0; if
(x == 0)
Printf("hi");
else
printf("how are
u"); printf("hello");
}
a. hi

63
b. how areyou
c. hello
d. hihello

64
PRACTICAL SET-13
String Recognization
Pattern searching is animportant problem in computer science.When we do searchfor astring
in notepad/word file or browser or database, pattern searching algorithms are used to show
the search results.
Matching Overview
txt = "AAAAABAAABA" pat =
"AAAA"
We compare first window of txt with pat
txt = "AAAAABAAABA"
pat = "AAAA" [Initial position]
We find a match. This is same as Naive String Matching. In the next step, we compare next
window of txt with pat.
txt = "AAAAABAAABA"
pat = "AAAA" [Pattern shifted one position]
This is where KMP does optimization over Naive. In this second window, we only compare fourth
A of pattern with fourth character of current window of text to decide whether current window
matches or not. Since we know first three characters will anyway match, we skipped matching
first three characters.

65
AIM: Write a program to recognize strings ‘aaab’, ‘abbb’, ‘ab’, and ‘a’ using grammar
Code:
LEX PART
YACC PART
%{
#include<stdio.h>
intvalid=1;
%}
%token A B
%%
str:S'n'{return0;}
S:A S B
|
;
%%
main()
{
printf("Enter the string:n");
yyparse();
if(valid==1)
printf("nvalid string");
}
%{
#include "y.tab.h"
%}
%%
a returnA;
b returnB;
.|n returnyytext[0];
%%

66
Output:
$ lex prog5b.l
$ yacc -d prog5b.y
$ cc -c lex.yy.c y.tab.c
$ cc -o a.out lex.yy.o y.tab.o -lfl
$ ./a.out
Enter the string: aaaabb
Invalid string
$ ./a.out
Enter the string: aaabbb
Valid string

67
Question Answers:
1. A language is represented by a regular expression (a)*(a+ ba). Which of the following
string does not belong to the regular set represented by the aboveexpression?
a. aaa
b. aba
c. ababa
d. aa
2. The following production rules of a regular grammar generate a language L: SaS /bS/
a / b The regular expression of Lis
a. a +b
b. (a +b)*
c. (a + b)(a +b)*
d. (aa + bb)a*b*
3. The regular expression (a/b)(a/b) denotes theset
a. { a, b, ab, aa}
b. { a, b, ba, bb}
c. Both a) andb)
d. None ofthese.
4. a*(a+b)* is equivalentto
a. a* +b*
b. a*b*
c. (ab)*
d. None ofthese

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